Doppler Distortion - Fact or Fiction

[Bob Cain]

I've got an argument that so far has withstood some scrutiny
which shows that Doppler distortion in a myth.

What would refute it and point out any flaw in the reasoning
would be the dynamical expression for the time varying
function of the pressure wave in an infinite tube with an
ideal piston as a function of an arbitrary, time varying
function of the force applied to that piston. I've asked
numerous places for that, including alt.sci.acoustics,
sci.physics and sci.physics.research and have looked hard
for a solution in the literature. Nothing to date. I think
there is a good reason for that; the force and pressure in
the wave are simply proportional and thus there is no such
thing as Doppler distortion. At least that is what my
reasoning from first principles says.

So I'm issuing a challenge to anyone here that thinks they
might be able to analyze it and produce an equation that
isn't a simple proportionality and is non-linear, as it must
be for the frequency modulation required of this so called
Doppler distortion. If you do it and it withstands peer
scrutiny, you get the pleasure of knowing that I have a
leather hat meal awaiting me (and the strong possiblity that
you've gone where no one else has gone before.) :-)

No heuristic arguments involving two tones, please, but a
real (or complex) equation that applies to any signal.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Phil Allison]

"Bob Cain"
>
> I've got an argument that so far has withstood some scrutiny
> which shows that Doppler distortion in a myth.


** Doppler distortion from what cause ???????

The air ?

Some moving cone driver ????




........... Phil

[William Sommerwerck]

I think there are two simple refutations, one theoretical, the other practical.

Theoretical -- If the output of a driver accurately follows its input waveform,
how can there be Doppler distortion?

Practical -- It should be trivial to compute the sidebands produced by combining
(say) a 60Hz signal and 6000 Hz signal. By looking at the phase of the
sidebands, it should be possible to determine what part of them is IM distortion
(AM components) and what part is Doppler (FM components).

[Phil Allison]

"William Sommerwerck"

> I think there are two simple refutations, one theoretical, the other
practical.
>
> Theoretical -- If the output of a driver accurately follows its input
waveform,
> how can there be Doppler distortion?


** No driver ever does that - the excursion quadruples every octave
lower you go for the same voltage input.


> Practical -- It should be trivial to compute the sidebands produced by
combining
> (say) a 60Hz signal and 6000 Hz signal. By looking at the phase of the
> sidebands, it should be possible to determine what part of them is IM
distortion
> (AM components) and what part is Doppler (FM components).
>

** Bob Cain never mentioned drivers at all.

He may well be referring to Doppler in the air itself.



.............. Phil

[Carey Carlan]

As a non-mathematical type I understood Doppler distortion to be caused
when a high frequency was generated by a driver already in motion with a
low frequency.

The example was a woofer moving full excursion on a very low tone while
generating a higher tone. Let's do an extreme case of a 10 Hz excursion
and a 1000 Hz tone. Every 20th of a second (change in direction at 10 Hz)
the pitch of the 1000 Hz tone would change as its vibrating medium (the
woofer cone) changed from moving toward the listener to moving away.

[Arny Krueger]

"Carey Carlan" > wrote in message
. 203

> As a non-mathematical type I understood Doppler distortion to be
> caused when a high frequency was generated by a driver already in
> motion with a low frequency.

That's it.

> The example was a woofer moving full excursion on a very low tone
> while generating a higher tone. Let's do an extreme case of a 10 Hz
> excursion and a 1000 Hz tone. Every 20th of a second (change in
> direction at 10 Hz) the pitch of the 1000 Hz tone would change as its
> vibrating medium (the woofer cone) changed from moving toward the
> listener to moving away.

Yes, that's it. Just like the whistle on a busy train engine in a switch
yard. No amplitude modulation distortion required.

I probably have an easier time than most with this sort of thing because of
my long-ago tour with Uncle Sam as a Doppler Radar technican.

If some of the arguments presented were taken to their logical conclusion,
the whole missle system I worked on would have never worked.

While high tech military toys of that era tended to be dodgy, the one I
worked on could at least partially work, and did I see the most important
parts of it work from incoming bogey to big bang in the sky.

[Arny Krueger]

"Bob Cain" > wrote in message


> I've got an argument that so far has withstood some scrutiny
> which shows that Doppler distortion in a myth.

> What would refute it and point out any flaw in the reasoning
> would be the dynamical expression for the time varying
> function of the pressure wave in an infinite tube with an
> ideal piston as a function of an arbitrary, time varying
> function of the force applied to that piston.

Fool that I am, I'm kinda stuck down here in the real world. Forget the
math, forget the long-winded discussions, the question that interests me
most is whether or not there's Doppler distortion where it really matters -
in the sound field in front of the speaker.

A couple of us have been pursuing the measurement route, and as often the
case the results are practically speaking, not all that startling.

First off, we've found that actually measuring Doppler distortion is not all
that easy. This is complexified by the fact that speakers have lots of
distortion of many kinds, and at most loudspeaker Doppler distortion is
relatively small. BTW, along the way, I've found reason to doubt a lot of
published jitter measurements. They don't seem to distinguish AM from FM.

But bottom line, we think we are measuring some Doppler distortion.
However, there's so many other kinds of distortion of a similar nature
happening at the same time, that it's practically a non-issue.

People who like looking at raw evidence can visit:
http://www.pcavtech.com/techtalk/doppler/ .

It might be most informative to compare these two sets of graphs and data:

"Triple Tone Lab Measurements - 316 millivolts RMS" and "Triple Tone Lab
Measurements - 10 Volts RMS"

Triple Tone Lab Measurements - 316 millivolts RMS shows a speaker operating
at a 1 meter SPL of about 78 dB. The background noise in the room actually
masks harmonics generated by the 50 Hz fundamental. Most visible distortion
products are 60 dB or more down (0.1%). Of course 0.1% is an absolutely
rediculously huge amount of distortion compared to the 0.003% THD that some
on RAP seem to want to worry about.

Triple Tone Lab Measurements - 10 Volts RMS shows a speaker operating at a
1 meter SPL of about 105 dB SPL. Don't be confused by the 1 meter SPL of 105
dB, out in the room the SPL is loud enough, but fairly modest (under 100 dB)
by modern standards.

Frankly, with 10 volts applied to its voice coil, this speaker has been
turned just about every which way but loose. 50 Hz THD is some place around
10%. IM is around 3%. It sounds pretty badly stressed, in real life.

The driver under test is a Peerless 6.5" speaker that is similar to what you
might find in one of the better near-field monitors. I would imagine that a
speaker like this would be rated for a maximum 1 meter SPL in excess of 110
dB. You can imagine how distorted it is under those conditions!

[Scott Dorsey]

Arny Krueger > wrote:
>"Bob Cain" > wrote in message
>
>> I've got an argument that so far has withstood some scrutiny
>> which shows that Doppler distortion in a myth.
>
>> What would refute it and point out any flaw in the reasoning
>> would be the dynamical expression for the time varying
>> function of the pressure wave in an infinite tube with an
>> ideal piston as a function of an arbitrary, time varying
>> function of the force applied to that piston.
>
>Fool that I am, I'm kinda stuck down here in the real world. Forget the
>math, forget the long-winded discussions, the question that interests me
>most is whether or not there's Doppler distortion where it really matters -
>in the sound field in front of the speaker.

Well, surprisingly enough, Phil actually made the good point that the woofer
position does not directly follow the input signal, but that the excursion
at lower frequencies is exaggerated. This is indeed the reason that we get
Doppler distortion. But, how do we compensate for this? And can we, even?

Of course, reducing the bandwidth to each driver and reducing the driver
excursion as much as possible are crude ways around the problem.

A more exaggerated example of the distortion, though, is found in coaxial
speakers where the moving woofer cone is used as the horn for the tweeter.
Here, though, I am not sure the math model is quite so easy, and it would
be interesting to see if anyone can model the boundary effects near the
moving woofer cone.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"Scott Dorsey" > wrote in message

> Arny Krueger > wrote:

>> "Bob Cain" > wrote in message

>>> I've got an argument that so far has withstood some scrutiny
>>> which shows that Doppler distortion in a myth.

>>> What would refute it and point out any flaw in the reasoning
>>> would be the dynamical expression for the time varying
>>> function of the pressure wave in an infinite tube with an
>>> ideal piston as a function of an arbitrary, time varying
>>> function of the force applied to that piston.

>> Fool that I am, I'm kinda stuck down here in the real world. Forget
>> the math, forget the long-winded discussions, the question that
>> interests me most is whether or not there's Doppler distortion where
>> it really matters - in the sound field in front of the speaker.

> Well, surprisingly enough, Phil actually made the good point that the
> woofer position does not directly follow the input signal, but that
> the excursion at lower frequencies is exaggerated. This is indeed
> the reason that we get Doppler distortion.

I would say that the exaggerated excursion at low frequencies is a
contributing cause for Doppler distortion, but not the only cause.

> But, how do we compensate for this? And can we, even?

> Of course, reducing the bandwidth to each driver and reducing the
> driver excursion as much as possible are crude ways around the problem.

Crude but effective! ;-)

Doppler is exactly proportional to the upper frequency being modulated. Drop
the upper crossover frequency on that woofer by a factor of two, and you
drop the Doppler distortion by 2. Double the diaphragm area, and you get the
same benefit. Subwoofers make even more sense!

BTW, this effect is the justification for the triple-tone tests posted at
http://www.pcavtech.com/techtalk/doppler/ . The FM-related sidebands on the
uppermost tone (4.25 KHz) will be about 4 times larger, compared to the
carrier, as those on the middle tone (1.0 KHz). The two tones are not even
multiples of each other so that the sidebands from each tone will not be
unlikely to land on top the sidebands of the other.

> A more exaggerated example of the distortion, though, is found in
> coaxial speakers where the moving woofer cone is used as the horn for
> the tweeter.

Yes, and I even have a KEF Q-15 to test that with.

However, our preliminary results show that even with a reasonable worst case
(small woofer, relatively high upper frequency) the Doppler tends to get
lost in the AM distortion. Claiming it isn't there is wrong, but getting
worked up about it seems a little foolish.

>Here, though, I am not sure the math model is quite so
> easy, and it would be interesting to see if anyone can model the
> boundary effects near the moving woofer cone.

It's tough enough to work with the case we're working with, which seems to
be far simpler.

[Scott Dorsey]

Arny Krueger > wrote:
>"Scott Dorsey" > wrote in message
>
>> Well, surprisingly enough, Phil actually made the good point that the
>> woofer position does not directly follow the input signal, but that
>> the excursion at lower frequencies is exaggerated. This is indeed
>> the reason that we get Doppler distortion.
>
>I would say that the exaggerated excursion at low frequencies is a
>contributing cause for Doppler distortion, but not the only cause.

On a typical full-range speaker _not_ breaking up, what other good
causes are there? With coaxials and with speakers in breakup, there
are all kinds of wacky things going on.

The only other cause I can think of has to do with compressibility of
air and it would seem to be a comparatively small issue.

>> But, how do we compensate for this? And can we, even?
>
>> Of course, reducing the bandwidth to each driver and reducing the
>> driver excursion as much as possible are crude ways around the problem.
>
>Crude but effective! ;-)
>
>Doppler is exactly proportional to the upper frequency being modulated. Drop
>the upper crossover frequency on that woofer by a factor of two, and you
>drop the Doppler distortion by 2.

That's reducing the bandwidth.

>Double the diaphragm area, and you get the
>same benefit.

That's reducing the driver excursion.

>Subwoofers make even more sense!

Yes, but they bring another whole set of issues along with them.

>> A more exaggerated example of the distortion, though, is found in
>> coaxial speakers where the moving woofer cone is used as the horn for
>> the tweeter.
>
>Yes, and I even have a KEF Q-15 to test that with.

A better one would be one of the Radian drivers, which are really bad about
it.

It would be interesting to see if the Urei horn assemblies on the Altec
coaxial drivers really do minimize doppler modulation compared with the
original Altec horn assemblies. That was one of the arguments the Urei
guys used for the extended horns they employed.

>However, our preliminary results show that even with a reasonable worst case
>(small woofer, relatively high upper frequency) the Doppler tends to get
>lost in the AM distortion. Claiming it isn't there is wrong, but getting
>worked up about it seems a little foolish.

Yes, but how audible is it? You can treat the doppler modulation sort of
like spurious sidebands, BUT they are sidebands that are modulated by
the signal. Does it make it mode or less audible than a fixed sideband?

>>Here, though, I am not sure the math model is quite so
>> easy, and it would be interesting to see if anyone can model the
>> boundary effects near the moving woofer cone.
>
>It's tough enough to work with the case we're working with, which seems to
>be far simpler.

Right, because you have pretty much one dominant distortion source, and it
is an easy one to model. You should be able to plug and chug and get a
simple value for doppler distortion due to increased excursion at low
frequencies, knowing little more than the tone frequencies and the driver
excursion for a given cabinet. How does that compare with the measured
doppler modulation on that cabinet? That will tell you if there are any
other hidden effects to worry about.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[U-CDK_CHARLES\\Charles]

"Bob Cain" > wrote in message
>
> I've got an argument that so far has withstood some scrutiny
> which shows that Doppler distortion in a myth.
>
> What would refute it and point out any flaw in the reasoning
> would be the dynamical expression for the time varying
> function of the pressure wave in an infinite tube with an
> ideal piston as a function of an arbitrary, time varying
> function of the force applied to that piston.
>

I would be willing to wager that it's damn near unmeasurable and
impossible to hear, compared to the other types of distortion
loudspeakers introduce.

Of course "It can be shown" that it exists for any mechanical
transducer--effectively a moving sound source, and be relatively easy to
calculate--it's a fairly straightforward manipulation of the wave
function for velocity, then make the velocity a function of the input
signal . . .

"Easy" to set up . . . but the algebra and trig gets a smidgeon knotty.

Anyone have Maple or Mathematica handy?

[Robert Morein]

"William Sommerwerck" > wrote in message
...
> I think there are two simple refutations, one theoretical, the other
practical.
>
> Theoretical -- If the output of a driver accurately follows its input
waveform,
> how can there be Doppler distortion?

If the driver converted voltage to air pressure, there could be no Doppler
distortion.
However, the driver, even under the best of circumstances, does not do that.
It converts, approximately, to displacement.

Displacement is not equivalent to air pressure.
>
> Practical -- It should be trivial to compute the sidebands produced by
combining
> (say) a 60Hz signal and 6000 Hz signal. By looking at the phase of the
> sidebands, it should be possible to determine what part of them is IM
distortion
> (AM components) and what part is Doppler (FM components).
>

[ScotFraser]

<< It would be interesting to see if the Urei horn assemblies on the Altec
coaxial drivers really do minimize doppler modulation compared with the
original Altec horn assemblies. That was one of the arguments the Urei
guys used for the extended horns they employed. >>

I think they traded one problem for another. By building the horn flare out
they may have avoided modulating the HF by the 15" cone, but in so doing they
also placed a substantial acoustic mask in front of the woofer. Still, the UREI
implementation was more successful than the Altec device it replaced, with its
hard edges, sectoral dividers, & straight sides.


Scott Fraser

[ScotFraser]

I recorded some violins, viola & cello through a nice speaker last week, a
lovely lacquered maple cabinet made by somebody named Leslie. I'll be damned if
there wasn't a ton of distortion AND doppler shifting. Just couldn't get rid of
it. It kind of made everybody seasick, but they all loved it anyway.

Scott Fraser

[William Sommerwerck]

Doppler distortion obviously exists. The question is one of how audible it is.

My feelings are "not very." You don't hear people who own full-range
electrostatics complaining about Doppler distortion.

Consider the following. Suppose an electrostatic speaker is reproducting 60Hz at
a peak-to-peak excursion of 0.25". That means its maximum velocity would be
around 30 inches per second. That's less than 1/4 of 1% of the speed of sound!

I really, really doubt that's audible.

[William Sommerwerck]

>> Consider the following. Suppose an electrostatic speaker is
>> reproducing 60Hz at a peak-to-peak excursion of 0.25".

>> That means its maximum velocity would be around 30 inches
>> per second. That's less than 1/4 of 1% of the speed of sound!

> It appears that a practical inter-electrode gap for an electrostatic
> speaker might be 2 mm or about 0.05". I believe that bad things
> might happen if the diaphragm traversed a great deal of that gap.

> In the +20 example posted at http://www.pcavtech.com/techtalk/doppler,
> the cone excursion was very roughly on the order of 1/8". There was
> a ton of distortion, almost all of which was AM distortion, not FM.

I deliberately chose an obviously extreme (!!!) situation to make the point.


> I admit it, my interest in Doppler distortion was peaked by someone
> who had doubts about high-Xmax woofers because of the exposure
> to Doppler distortion.

piqued

[JoVee]

so, anybody see where bob went...?

[Bob Cain]

William Sommerwerck wrote:

> I think there are two simple refutations, one theoretical, the other practical.
>
> Theoretical -- If the output of a driver accurately follows its input waveform,
> how can there be Doppler distortion?

Precisely, and an argument by reciprocity shows that to be
the case. If you measure the particle (voxel if you don't
like discrete) velocity and then make the reproducing system
follow that velocity function then what goes out as a wave
will be the same as what was measured.

>
> Practical -- It should be trivial to compute the sidebands produced by combining
> (say) a 60Hz signal and 6000 Hz signal. By looking at the phase of the
> sidebands, it should be possible to determine what part of them is IM distortion
> (AM components) and what part is Doppler (FM components).
>

Non-linearities mix in very wierd ways. The only real
experimental test would require a super-linear driver and
those are hard to find.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Robert Morein wrote:


> If the driver converted voltage to air pressure, there could be no Doppler
> distortion.
> However, the driver, even under the best of circumstances, does not do that.
> It converts, approximately, to displacement.

I'm afraid this is incorrect. The heuristics usually used
to describe this effect apply equally well to an ideal
system where a massless, infinitely compliant and lossless
piston is driven by a force function.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Scott Dorsey]

William Sommerwerck > wrote:
>Doppler distortion obviously exists. The question is one of how audible it is.
>
>My feelings are "not very." You don't hear people who own full-range
>electrostatics complaining about Doppler distortion.
>
>Consider the following. Suppose an electrostatic speaker is reproducting 60Hz at
>a peak-to-peak excursion of 0.25". That means its maximum velocity would be
>around 30 inches per second. That's less than 1/4 of 1% of the speed of sound!

Right, but this is a speaker that has a huge surface area and therefore has
a very low total excursion. This is a _good_ thing. When your woofer
excursion starts getting to be an order of magnitude larger, the numbers
change. But the large surface area of an electrostatic panel means you can
get considerable bass without substantial excursion... which is good because
nonlinearities in the field become a big issue when there is substantial
excursion.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Bob Cain]

Carey Carlan wrote:

> As a non-mathematical type I understood Doppler distortion to be caused
> when a high frequency was generated by a driver already in motion with a
> low frequency.

That's the definition. What is needed to put the question
to bed is a general dynamical equation for what happens at a
piston-air interface which will yield that result when
applied to a sum of such sinusiods. No such equation has
been forthcoming in places where it should be a trivial
exercise for those in attendance.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Arny Krueger wrote:

> Fool that I am, I'm kinda stuck down here in the real world. Forget the
> math,

Then we are whistling in the dark. I admire your
experimentalist approach. Experiment trumps theory, always.

I just ask that you draw no conclusions from a system that
contains measurable non-linearity in the transducer itself.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Robert Morein]

"William Sommerwerck" > wrote in message
...
> Doppler distortion obviously exists. The question is one of how audible it
is.
>
> My feelings are "not very." You don't hear people who own full-range
> electrostatics complaining about Doppler distortion.
>
> Consider the following. Suppose an electrostatic speaker is reproducting
60Hz at
> a peak-to-peak excursion of 0.25". That means its maximum velocity would
be
> around 30 inches per second. That's less than 1/4 of 1% of the speed of
sound!
>
> I really, really doubt that's audible.
>
Electrostatics should be less prone to doppler than many other speakers,
because of the large diaphram size.
1/4" is an impossible excursion for an electrostatic, because electric force
is much weaker than magnetic force.
The diaphrams of these speakers move minutely, inversely proportional to the
size of the diaphram for a given SPL.

The most serious examples would be:
1. a two-way, with a bass/mid driver that's really pumping
2. A three-way with a small driver optimized for dispersion, in which case
both the bass and mid drivers might be stressed.

I'm not commenting on the audibility of Doppler, only that an electrostat is
not a good example.

I do own Acoustat 2+2's, and I do not complain about Doppler distortion :)
Unless it were introduced to me in a laboratory setting, I would have no way
of recognizing it.

[Bob Cain]

Scott Dorsey wrote:


> No. If the motion of the cone perfectly follows the waveform, and the air
> is not compressable, the pressure waveform that results in the air will be
> a perfect representation of the original wave. If you can somehow arrange
> for perfect coupling so that the woofer excursion perfectly matches the
> input signal, doppler effects should be a non-issue. Unfortunately this
> does not go along well with accurate frequency response in the real world.

However, for it to be a real, non-linear effect it must be
demonstrable in a hyperlinear transducer. All linear
imperfections in the system can be cancelled by a suitable
linear function block between the input and the transducer
such that the cone follows the waveform. If there are
non-linearities in the transducer all bets are off because
we don't really know what is the cause of the resulting
non-linear output.

[theory alert]
The reason that it must be a non-linear effect is that any
linear system has sinusoids as eigenfunctions.
Eigenfunctions are those functions which when presented to
the system as input, in any summation, result in an output
that contains only complex scalings of the magnitudes of the
input eigenfunctions, which are called the eigenvalues.
Scaling zero results in zero which means that no non-zero
eigenvalues can result in the output which were zero in the
input. The hypothetical Doppler distortion fails this test.
[end alert]


> Right. It's very easy to model that effect.

Actually, for an arbitrary input it has not been done.
There is no model even that will quantitatively predict the
measured result of experiments with two tones.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[William Sommerwerck]

>> Doppler distortion obviously exists. The question is one of how audible it
is.
>> My feelings are "not very." You don't hear people who own full-range
>> electrostatics complaining about Doppler distortion.

>> Consider the following. Suppose an electrostatic speaker is reproducting 60Hz
at
>> a peak-to-peak excursion of 0.25". That means its maximum velocity would be
>> around 30 inches per second. That's less than 1/4 of 1% of the speed of
sound!

> Right, but this is a speaker that has a huge surface area and therefore has
> a very low total excursion. This is a _good_ thing. When your woofer
> excursion starts getting to be an order of magnitude larger, the numbers
> change. But the large surface area of an electrostatic panel means you can
> get considerable bass without substantial excursion... which is good because
> nonlinearities in the field become a big issue when there is substantial
> excursion.

All correct, but multi-way dynamic systems with such large excursions eliminate
much of the potential for Doppler distortion, simply because the higher
frequencies are reproduced through a separate driver.

Note, also, that such a large excursion would usually occur on a bass transient,
not during "normal" (???) music.

[Goofball_star_dot_etal]

On Wed, 11 Aug 2004 10:56:27 -0700, Bob Cain
> wrote:

>
>
>Arny Krueger wrote:
>
>> Fool that I am, I'm kinda stuck down here in the real world. Forget the
>> math,
>
>Then we are whistling in the dark. I admire your
>experimentalist approach. Experiment trumps theory, always.
>
>I just ask that you draw no conclusions from a system that
>contains measurable non-linearity in the transducer itself.
>
>

That does not seem fair. . .

>Bob
>--
>
>"Things should be described as simply as possible, but no
>simpler."
>
> A. Einstein

[Arny Krueger]

"Bob Cain" > wrote in message


> Arny Krueger wrote:

>> Fool that I am, I'm kinda stuck down here in the real world. Forget
>> the math,

> Then we are whistling in the dark. I admire your
> experimentalist approach. Experiment trumps theory, always.

> I just ask that you draw no conclusions from a system that
> contains measurable non-linearity in the transducer itself.

I think that's being too restrictive. We have at least two ways to
distinguish AM from FM. The fact that we're finding so much AM is probably a
guide to the most practical answer.

[Scott Dorsey]

William Sommerwerck > wrote:
>>> Consider the following. Suppose an electrostatic speaker is reproducting 60Hz
>at
>>> a peak-to-peak excursion of 0.25". That means its maximum velocity would be
>>> around 30 inches per second. That's less than 1/4 of 1% of the speed of
>sound!
>
>> Right, but this is a speaker that has a huge surface area and therefore has
>> a very low total excursion. This is a _good_ thing. When your woofer
>> excursion starts getting to be an order of magnitude larger, the numbers
>> change. But the large surface area of an electrostatic panel means you can
>> get considerable bass without substantial excursion... which is good because
>> nonlinearities in the field become a big issue when there is substantial
>> excursion.
>
>All correct, but multi-way dynamic systems with such large excursions eliminate
>much of the potential for Doppler distortion, simply because the higher
>frequencies are reproduced through a separate driver.

In most cases, yes. When Doppler distortion becomes a big problem is in
systems like the Lowther when you have both large excursions and wide
bandwidth through a driver. Or, in coaxial systems, where the seperate
driver is still using the bass driver cone. In typical multi-way systems,
the issue is much smaller.

>Note, also, that such a large excursion would usually occur on a bass transient,
>not during "normal" (???) music.

Right. But what if if the string section is playing a nice long note that
is held for a while, and there is a hit on the tympani? Can you hear the
strings being modulated? The "Ondekoza" track I submitted to one of the RAP
CDS should be a real torture test since it has some clean flute notes combined
with heavy low end . I can't hear any modulation at all on the Magnepans,
but I can hear lots on my father's old Wharfdales (which have 6 dB/octave
crossovers on the top and bottom and run the midrange full range).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Ben Bradley]

On Wed, 11 Aug 2004 11:47:23 -0400, "Arny Krueger" >
wrote:

>"Scott Dorsey" > wrote in message


>>If the motion of the cone perfectly follows the waveform, and
>> the air is not compressable,

Air is compressible, even water is compressible, and that's why the
speed of sound in air and water are finite.

>> the pressure waveform that results in
>> the air will be a perfect representation of the original wave.
>
>Scott, I think you've missed a critical point. A speaker is a transducer,
>and that means that in the process of following the waveform ideally, the
>results in the air can be a little different than what was intended.
>
>> If you can somehow arrange for perfect coupling so that the woofer
>> excursion perfectly matches the input signal, doppler effects should
>> be a non-issue.

If you made a transducer that increases and decreases the air
pressure without using physical movement, there would be no doppler
distortion. You could have two valves that alternately open and close,
connected to a source of compressed air and the other to a vacuum,
which would cause increase and decrease in air pressure without
movement, but this doesn't seem practical for good audio reproduction.
The problem is that the cone moves, and its movement is significant
in relation to the speed of sound in air.

>No. Imperfect woofer excursion is more along the line of AM effects.
>
>> Unfortunately this does not go along well with
>> accurate frequency response in the real world.
>
>I think that this issue of imperfect cone motion has some light shed on it
>by contemplating a system with a tweeter, versus a system that lacks one. In
>both cases the respective signals are transduced into the air with ideal
>waveforms. The Doppler comes from the fact that the HF gets transduced into
>the air from a platform with large-scale motion due to some other signal.
>The tweeter does not have this situation.
>
>It's like the train whistle. The whistle itself need not be affected by its
>motion through the air. The fact that the whistle is moving w/r/t the
>listener

AND that the speed of sound is finite, and that the speed of the
train is a significant percentage of the speed of sound...

>is the root cause of the Doppler effect.

A lot of stuff has already been covered (and uncovered and
discovered and recovered...) on "another forum." If anyone wants to
read some "background info" before posting further (I suggest it just
to see what has already been rehashed), read these threads "Drum dB's"
and "Doppler Distoriton?" on alt.music.home-studio:

http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&threadm=YOHRc.3553%24LH.817%40bignews4.bellsouth.n et&prev=/groups%3Fq%3Dalt.music.home-studio%26ie%3DUTF-8%26hl%3Den%26btnG%3DGoogle%2BSearch
or
http://makeashorterlink.com/?R2DD35609

http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&threadm=cf9fv202ass%40enews4.newsguy.com&prev=/groups%3Fq%3Dalt.music.home-studio%26ie%3DUTF-8%26hl%3Den%26btnG%3DGoogle%2BSearch
or
http://makeashorterlink.com/?H2ED62609

And a heads up, "Porky" over there is quite similar in demeanor to
"Phil Allison" here on RAP.

-----
http://mindspring.com/~benbradley

[Bob Cain]

U-CDK_CHARLES\Charles wrote:

>
> Of course "It can be shown" that it exists for any mechanical
> transducer--effectively a moving sound source, and be relatively easy to
> calculate--it's a fairly straightforward manipulation of the wave
> function for velocity, then make the velocity a function of the input
> signal . . .
>
> "Easy" to set up . . . but the algebra and trig gets a smidgeon knotty.
>
> Anyone have Maple or Mathematica handy?

Nope, or I'd lend it to you. If it can be "shown" in a
fully general way that withstands scrutiny I really want to
know the answer.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Robert Morein wrote:


>>I'm afraid this is incorrect. The heuristics usually used
>>to describe this effect apply equally well to an ideal
>>system where a massless, infinitely compliant and lossless
>>piston is driven by a force function.
>>
>
> 1. You can't contradict what I said with a heuristic. See
> http://www.hyperdictionary.com/dictionary/heuristic

I'm not trying to; I'm trying to cast doubt on the heuristic
description. All too often when this is attempted, the
result is a failure of intuition.

>
> 2. The "heuristic", by which you probably mean approximation, is exactly
> that and no more, a very useful approximation.

Can you state an expression for it? That, if it is
justifiable from first principles, eliminates heuristics.

>
> 3. The subject under discussion is whether the "heuristic" breaks down in a
> meaningful fashion. This is the very core of the discussion. If Doppler
> effect influences the sound output, then, to the extent which it does, the
> "heuristic" is invalid.

No, it is whether it has any validity at all.

>
> 4. I do not imply by the above that Doppler is important, or is not. But
> please understand that the following is an equivalence relationship:
>
> a. If Doppler is unimportant, then the heuristic you mention is, for all
> practical purposes, a very good one.

It is just hand waving to this point.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Ben Bradley wrote:


>
> If you made a transducer that increases and decreases the air
> pressure without using physical movement, there would be no doppler
> distortion.

Impossible on first principles of acoustics. Increasing and
decreasing the air pressure results in totally predictable
changes in the velocity of the air. The are simply
proportional through the (real) characteristic impedence of air.

If the SPL is high enough, yes, nonlinearities occur in the
air and the above isn't true but you have to get pretty
darned high for that to have any signifigance. At the
levels we listen to, air is highly linear.

My argument is simply that if you can reproduce velocity of
air then by the above, the pressure has no choice but to
remain in phase and proportional if it remains in the linear
regime. If you can measure it you can reproduce it by
moving a piston with the measured velocity. Exactly. The
resulting pressure wave contains no distortion.

The above argument stands whether we are talking about
reproducing pressure or velocity because in air they are in
phase and proportional in a plane wave and deviations from
planarity only have linear consequences.


> And a heads up, "Porky" over there is quite similar in demeanor to
> "Phil Allison" here on RAP.

Actually, Porky has been nothing but congenial and careful
of late. It was on that tentative basis that I chose to
address his post.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Arny Krueger]

"Bob Cain" > wrote in message

> Arny Krueger wrote:
>
>>> I just ask that you draw no conclusions from a system that
>>> contains measurable non-linearity in the transducer itself.
>>
>>
>> I think that's being too restrictive. We have at least two ways to
>> distinguish AM from FM. The fact that we're finding so much AM is
>> probably a guide to the most practical answer.
>
> Arny, when you start mixing distributed non-linearities such
> as that in the surround, that of cone distortion, that of
> the magnetic circuit, etc. It is not generally possible to
> describe the resulting form of distortion.

What, whether it is AM or FM or what proportion of which?

Sources don't matter, all that matter is a clean enough signal to analyze.

> It most likely
> involves recursion and thus results in chaotic effects. I
> can see no reason why FM cannot occur as a consequence of
> these mixed factors. Just about any form of non-linearity
> can result from them.

Lets go down your list:

(1) that in the surround - doesn't matter where the Doppler comes from,
just that it is.
(2) that of cone distortion - doesn't matter where the Doppler comes from,
just that it is.
(3) the magnetic circuit - not moving, so it can't cause Doppler


> In fact, when I simulated a simple model of the described
> effect, the distortion produced was chaotic and broadband,
> not isolated spectral lines.

We get pretty clean isolated spectral lines from real-world measurements.
Guess what that says about the simulation?

>Until that can be done the effect described remains hypothetical from an
experimental standpoint.

We don't need a working theory to have believable experimental results.

[Chris Hornbeck]

On Wed, 11 Aug 2004 10:56:27 -0700, Bob Cain
> wrote:

>I just ask that you draw no conclusions from a system that
>contains measurable non-linearity in the transducer itself.

No amplitude non-linearity is needed to generate phase or
frequency modulation.

I'm not following this discussion at all. Are you asking
if a train whistle's pitch changes as it passes by?

Or that a recorded train whistle played through a speaker
doesn't change pitch as it passes by?


Chris Hornbeck

[Arny Krueger]

""Granma" Dave Schein II, CSO" > wrote in message


> In layman's terms, what, exactly, is Doppler Distortion?

http://www.swee****er.com/insync/word.php?find=Doppler

The Doppler effect, named after a German physicist (how come things are
always named after a German physicist?), is the apparent change in pitch of
the sound that occurs when the source of the sound is moving relative to the
listener. For example: A car horn will sound higher in pitch as it
approaches, and lower in pitch after it passes us. This is one principle
that is employed in a rotating speaker system like a Leslie. The rapid
movement of the horn to and away from the listener creates a sort of vibrato
effect. There are many modern effects units that simulate the Leslie sound,
and also offer other types of Doppler effects.

If a loudspeaker is producing both low and high frequencies, the low
frequencies will cause the cone to move alternatingly toward and away from
the listener (obviously high frequencies do this too, but the lows are much
more pronounced). As this is happening the perceived pitch of the higher
frequency sounds rise and fall at a rate (or rates) equal to the low
frequencies moving the cone. This is actually Frequency Modulation of the
high frequency by the low frequency, and is called "Doppler Distortion." It
manifests itself as a sort of "muddiness" (subjective audio term #108) of
the sound.

[\Granma\ Dave Schein II, CSO]

wow! NEAT!

It makes total sense, but I had never thought about it in terms of Doppler.
I have found this to be a problem with my home stereo, and I've solved it in
my own experience by using crossovers and filters to isolate the output of
the speakers.

A question about the Leslie, though: I thought the Leslie had two speakers,
one high and one low, rotating at user-defined rates. Would that cause
Doppler, or simply a tremolo effect based around the directionality of the
speaker? I.e., if the speaker is pointed away from the microphone (or ear),
the volume would be softer, and vice-versa?

Thank you for your information,

-gran

--
Dave Schein II, CSO
Printergy, Inc. - Moving a Million Documents to the Web!
www.printergy.com
DOCHighway, Inc. - Wherever You Are! Wireless!
www.dochighway.com
CDs, DVDs, Scanning, Document Management, Knowledge Sharing...
...The Future!
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443-803-2119 - Direct


"Arny Krueger" > wrote in message
...
> ""Granma" Dave Schein II, CSO" > wrote in message
>
>
> > In layman's terms, what, exactly, is Doppler Distortion?
>
> http://www.swee****er.com/insync/word.php?find=Doppler
>
> The Doppler effect, named after a German physicist (how come things are
> always named after a German physicist?), is the apparent change in pitch
of
> the sound that occurs when the source of the sound is moving relative to
the
> listener. For example: A car horn will sound higher in pitch as it
> approaches, and lower in pitch after it passes us. This is one principle
> that is employed in a rotating speaker system like a Leslie. The rapid
> movement of the horn to and away from the listener creates a sort of
vibrato
> effect. There are many modern effects units that simulate the Leslie
sound,
> and also offer other types of Doppler effects.
>
> If a loudspeaker is producing both low and high frequencies, the low
> frequencies will cause the cone to move alternatingly toward and away from
> the listener (obviously high frequencies do this too, but the lows are
much
> more pronounced). As this is happening the perceived pitch of the higher
> frequency sounds rise and fall at a rate (or rates) equal to the low
> frequencies moving the cone. This is actually Frequency Modulation of the
> high frequency by the low frequency, and is called "Doppler Distortion."
It
> manifests itself as a sort of "muddiness" (subjective audio term #108) of
> the sound.
>
>

[Scott Dorsey]

\"Granma\" Dave Schein II, CSO > wrote:
>wow! NEAT!
>
>A question about the Leslie, though: I thought the Leslie had two speakers,
>one high and one low, rotating at user-defined rates. Would that cause
>Doppler, or simply a tremolo effect based around the directionality of the
>speaker? I.e., if the speaker is pointed away from the microphone (or ear),
>the volume would be softer, and vice-versa?

This is true, but the pitch also changes as the thing rotates. Play a
note, and you not only hear tremolo caused by changing amplitude, you
also hear vibrato caused by changing frequency. This is part of why the
Leslie is so hard to model accurately and why most of the Leslie simulators
don't sound like the real thing.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Edi Zubovic]

On 11 Aug 2004 18:14:09 -0400, (Scott Dorsey) wrote:

>\"Granma\" Dave Schein II, CSO > wrote:
>>wow! NEAT!
>>
>>A question about the Leslie, though: I thought the Leslie had two speakers,
>>one high and one low, rotating at user-defined rates. Would that cause
>>Doppler, or simply a tremolo effect based around the directionality of the
>>speaker? I.e., if the speaker is pointed away from the microphone (or ear),
>>the volume would be softer, and vice-versa?
>
>This is true, but the pitch also changes as the thing rotates. Play a
>note, and you not only hear tremolo caused by changing amplitude, you
>also hear vibrato caused by changing frequency. This is part of why the
>Leslie is so hard to model accurately and why most of the Leslie simulators
>don't sound like the real thing.
>--scott

So I've often wondered whether a Leslie was more acoustical than
electrical instrument <g>.

Edi Zubovic, Crikvenica, Croatia

[William Sommerwerck]

> What, whether it is AM or FM or what proportion of which?

> Sources don't matter, all that matter is a clean enough signal to analyze.

Point... My memory of modulation theory is that the only difference between AM
and weak FM is the phase of the sidebands. (This is how modern high-powered AM
transmitters are built -- the carrier is weakly FM modulated, then amplified,
then goes through a phase shifter. Or something like that.)

So... If you analyze the sideband frequencies into their AM (in-phase) and FM
(quadrature) components, you have the relative amounts of IM and Doppler
distortion.

The FM component is, by definition, Doppler distortion. (Right? ???) So its
source or cause doesn't matter.

[William Sommerwerck]

> The Doppler effect, named after a German physicist (how come
> things are always named after a German physicist?)...

They aren't. I own lots of Land cameras, and they're named after a
Russian/American physicist.

[Mike Tulley]

On Wed, 11 Aug 2004 01:31:04 -0700, Bob Cain
> wrote:

>
>I've got an argument that so far has withstood some scrutiny
>which shows that Doppler distortion in a myth.
>
>What would refute it and point out any flaw in the reasoning
>would be the dynamical expression for the time varying
>function of the pressure wave in an infinite tube with an
>ideal piston as a function of an arbitrary, time varying
>function of the force applied to that piston. I've asked
>numerous places for that, including alt.sci.acoustics,
>sci.physics and sci.physics.research and have looked hard
>for a solution in the literature. Nothing to date. I think
>there is a good reason for that; the force and pressure in
>the wave are simply proportional and thus there is no such
>thing as Doppler distortion. At least that is what my
>reasoning from first principles says.
>
>So I'm issuing a challenge to anyone here that thinks they
>might be able to analyze it and produce an equation that
>isn't a simple proportionality and is non-linear, as it must
>be for the frequency modulation required of this so called
>Doppler distortion. If you do it and it withstands peer
>scrutiny, you get the pleasure of knowing that I have a
>leather hat meal awaiting me (and the strong possiblity that
>you've gone where no one else has gone before.) :-)
>
>No heuristic arguments involving two tones, please, but a
>real (or complex) equation that applies to any signal.
>
>
>Bob

I think I understand what you're getting at, so let me restate it
non-mathermatically, for those of us who are sound techs rather than
audio engineers.

Example 1:

I take a tiny 2" speaker, and mount in on the center of an 18"
high-excursion driver. The tiny speaker has tiny wires leading to a
tiny amplifier. I drive it with 4KHz; it reproduces the tone.

Now I drive the 18" driver with 50Hz at maximum excursion. I hear a
50Hz vibrato on the 4KHz tone. This is Doppler distortion.

Example 2:

I generate a 4 KHz tone and a 50Hz tone. I sum them, and feed them to
a full-range speaker through an amplifier with low IM distortion. From
the speaker, I hear 4KHz and 50Hz. No vibrato, because the speaker is
accurately reproducing the waveform that is the sum of the two tones.
No Doppler distortion.

Example 3:

I take the full range speaker which is accurately reproducing the
two-tone waveform, and shake it rapidly back and forth, toward and
away from the listener. The listener hears variations in pitch.
Dopppler distortion.

Mike T.

[William Sommerwerck]

> Example 2:

> I generate a 4 KHz tone and a 50Hz tone. I sum them, and feed them to
> a full-range speaker through an amplifier with low IM distortion. From
> the speaker, I hear 4KHz and 50Hz. No vibrato, because the speaker is
> accurately reproducing the waveform that is the sum of the two tones.
> No Doppler distortion.

Well... No. The 4kHz signal is being reproduced from a source that is moving
with respect to the listener.

[Bob Cain]

Arny Krueger wrote:


>>Why? Separation of variables is essential to an experiment
>>attempting to measure the consequences of one effect.
>
>
> The reason is quite clear. The question at hand is about loudspeaker
> Doppler distortion. All known loudspeakers have copious amounts of
> measurable nonlinearity.. If we disallow experimental results from
> loudspeakers that have measurable non-linearity, we disallow all experiments
> with loudspeakers.

And rightfully so.

Please believe that I'm not trying to be right here but just
correct. I will be just as happy if someone can come up
with the formal theoretical underpinning of this
hypothetical phenomenon as I will if it is found that there
isn't one.

So far no physicist or acoustician that reads usenet has
even tried in public. What's up with that? It's not like
it's an uninteresting problem.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[ScotFraser]

<< A question about the Leslie, though: I thought the Leslie had two
speakers,>>

Yes.

<<one high and one low, rotating at user-defined rates.>>

There are two speeds, slow & fast, controllable from the organ console. You can
trim these speeds somewhat within the unit, although it isn't a realtime
performance control. And, there are two motors, so some customization is
possible by offsetting the low & high frequency slow & fast speeds. BTW, they
rotate in opposite directions.

<< Would that cause
Doppler, or simply a tremolo effect based around the directionality of the
speaker? I.e., if the speaker is pointed away from the microphone (or ear),
the volume would be softer, and vice-versa?
>>

It's complex. There is amplitude modulation, frequency modulation, phase
modulation, timbre modulation, varying amounts of overdive distortion from the
tube amps, & a whole lot of reflections inside the cabinet. In a word, they
sound fantastic.


Scott Fraser

[Kurt Riemann]

On 11 Aug 2004 18:14:09 -0400, (Scott Dorsey) wrote:

>\"Granma\" Dave Schein II, CSO > wrote:
>>wow! NEAT!
>>
>>A question about the Leslie, though: I thought the Leslie had two speakers,
>>one high and one low, rotating at user-defined rates. Would that cause
>>Doppler, or simply a tremolo effect based around the directionality of the
>>speaker? I.e., if the speaker is pointed away from the microphone (or ear),
>>the volume would be softer, and vice-versa?
>
>This is true, but the pitch also changes as the thing rotates. Play a
>note, and you not only hear tremolo caused by changing amplitude, you
>also hear vibrato caused by changing frequency. This is part of why the
>Leslie is so hard to model accurately and why most of the Leslie simulators
>don't sound like the real thing.
>--scott

Actually in a leslie the horn in front of the driver rotates, the
speaker driver remains stationary. Which creates a much more complex
phenomena than mere doppler. Doppler is supposedly in there but there
a lot of complex wavefronts being combed at once as that baby turns
insude a hard-walled cabinet, which is why simulators are too clean in
comparison. I personally hear more phasing than doppler. Someday I'll
pump a sine wave through it

Also - only one of the sides of the spinning horn is open, the other
is closed off. Unless some rocker cracked it off.

I'm sure there's literature on the Doppler effect in a Leslie, but
Doppler it's a very small component of the "sound", most of the tone
comes from the combing. You need to spend some time in front of one of
those beasts to appreciate it. I read in here once that "recording a
Leslie is like taking a picture of a sunset." Not quite the same
dimension as the original experience.



Kurt Riemann

[Bob Cain]

Arny Krueger wrote:


>>Arny, when you start mixing distributed non-linearities such
>>as that in the surround, that of cone distortion, that of
>>the magnetic circuit, etc. It is not generally possible to
>>describe the resulting form of distortion.
>
>
> What, whether it is AM or FM or what proportion of which?

Whether it is even formally describable.

>
> Sources don't matter, all that matter is a clean enough signal to analyze.

The hell they don't. If what is generating the data to be
measured cannot be characterized then neither can the data.


> Lets go down your list:
>
> (1) that in the surround - doesn't matter where the Doppler comes from,
> just that it is.

I don't follow this.

> (2) that of cone distortion - doesn't matter where the Doppler comes from,
> just that it is.'

This either.

> (3) the magnetic circuit - not moving, so it can't cause Doppler

I understand this one. The question remains whether FM can
be ruled out of an active system that has these forms of
distortion in a distributed and interacting fashion. Can it?

>>In fact, when I simulated a simple model of the described
>>effect, the distortion produced was chaotic and broadband,
>>not isolated spectral lines.
>
>
> We get pretty clean isolated spectral lines from real-world measurements.
> Guess what that says about the simulation?

What's it say about the system under test? What does it
specifically say about Doppler distortion?


> We don't need a working theory to have believable experimental results.

Absolutely agreed, but to have a believable experimental
result all factors that can contribute to the data in the
same way that the phenomenon being investigated can must
either be completely characterized or eliminated. This is
fundamental.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Arny Krueger]

"William Sommerwerck" > wrote in message

>> What, whether it is AM or FM or what proportion of which?
>
>> Sources don't matter, all that matter is a clean enough signal to
>> analyze.

> Point... My memory of modulation theory is that the only difference
> between AM and weak FM is the phase of the sidebands. (This is how
> modern high-powered AM transmitters are built -- the carrier is
> weakly FM modulated, then amplified, then goes through a phase
> shifter. Or something like that.)

Agreed.

> So... If you analyze the sideband frequencies into their AM
> (in-phase) and FM (quadrature) components, you have the relative
> amounts of IM and Doppler distortion.

Agreed.

And what we find is a mixture of AM distortion and FM distortion.

A number of other tests pass, as well.

> The FM component is, by definition, Doppler distortion. (Right? ???)

Agreed.

> So its source or cause doesn't matter.

[Chris Hornbeck]

On Wed, 11 Aug 2004 01:31:04 -0700, Bob Cain
> wrote:

>So I'm issuing a challenge to anyone here that thinks they
>might be able to analyze it and produce an equation that
>isn't a simple proportionality and is non-linear, as it must
>be for the frequency modulation required of this so called
>Doppler distortion.

OK, now I see the problem. Frequency modulation doesn't
require and, in fact, is independent of, non-linearity in
the sense used here.

FM sidebands are Bessel functions generated by expanding
the right hand side of an expression that includes angular
velocities and frequencies *only*. IOW, "linear".

Chris Hornbeck

[Bob Cain]

Mike Tulley wrote:


> I think I understand what you're getting at, so let me restate it
> non-mathermatically, for those of us who are sound techs rather than
> audio engineers.

Disqualified. :-)

>
> Example 1:
>
> I take a tiny 2" speaker, and mount in on the center of an 18"
> high-excursion driver. The tiny speaker has tiny wires leading to a
> tiny amplifier. I drive it with 4KHz; it reproduces the tone.
>
> Now I drive the 18" driver with 50Hz at maximum excursion. I hear a
> 50Hz vibrato on the 4KHz tone. This is Doppler distortion.

No you won't and I'm going to explain why in a response to
my original post since this argument in various forms has
come up frequently and was in fact the original motivation
for thinking there was such a thing.

The flaw in this and the traditional reasoning finally came
to me just now with a response to you in progress and
pending while I watched the news. Stay tuned to this
thread. :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

I've been really stuck finding the flaw in the traditional
arguement for Doppler distortion and in some of the
scenarios that have been presented here in argument for it.
It finally just came to me.

It's really simple and even easy to understand. Doppler
shift is a phenomenon that occurs when a source is moving
with respect to the medium or _through_ the medium in which
it is generating a wave. In the case of a loudspeaker, or a
little one mounted on a big one, or whatever, it is not
moving with respect to the medium, it is moving the medium.
There is a fundamental difference.

In the situation presented of a little speaker mounted on a
big one, you will get Doppler distortion only if the big one
is acoustically transparent. When it is acoustically rigid
you have an entirely different situation and no Doppler
distortion will occur.

Doppler distortion in loudspeakers is a dead issue. It does
not exist. I cannot explain the posted data other than to
wonder if the effect was accidently in the input data.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Phil Allison]

"William Sommerwerck" > wrote in message
...
> Doppler distortion obviously exists. The question is one of how audible it
is.
>
> My feelings are "not very." You don't hear people who own full-range
> electrostatics complaining about Doppler distortion.
>
> Consider the following. Suppose an electrostatic speaker is reproducting
60Hz at
> a peak-to-peak excursion of 0.25". That means its maximum velocity would
be
> around 30 inches per second. That's less than 1/4 of 1% of the speed of
sound!
>
> I really, really doubt that's audible.
>


** Try modulating a 2000 Hz tone so the frequency shifts up and down by 5
Hz - see how wrong you are.


BTW ES speakers have large diaphragm areas and small excursions so they
have less Doppler than cone
speakers.



............... Phil

[Chris Hornbeck]

On Wed, 11 Aug 2004 16:58:54 -0700, Bob Cain
> wrote:

>> No amplitude non-linearity is needed to generate phase or
>> frequency modulation.
>
>I don't know what amplitude non-linearity is. I described
>what linearity is in another post. When distributed linear
>and non-linear factors are all mixed up with an energy
>source driving the whole thing there isn't a whole lot that
>can be said about what can come out of it.

By amplitude non-linearity I only mean the stuffs in the
transfer function errors that don't include time.
Harmonic and intermodulation distortions; like that.

FM doesn't require any amplitude non-linearity. That may
be the source of several posters' confusions. It's an
interesting topic. (May you live in interesting topics!)

Chris Hornbeck

[Chris Hornbeck]

On Wed, 11 Aug 2004 18:26:42 -0700, "William Sommerwerck"
> wrote:

>Question: How does the air in front of the speaker "distinguish" between the
>cone moving back and forth, and the driver as a whole being moved back and forth
>(without any signal applied to the voice coil) at the same rate and amplitude?

Exactly right. This can be restated as "air is very low impedance".
Conventional speakers operate into something close to a short
circuit.

Chris Hornbeck

[Scott Dorsey]

Chris Hornbeck > wrote:
>On Wed, 11 Aug 2004 01:31:04 -0700, Bob Cain
> wrote:
>
>>So I'm issuing a challenge to anyone here that thinks they
>>might be able to analyze it and produce an equation that
>>isn't a simple proportionality and is non-linear, as it must
>>be for the frequency modulation required of this so called
>>Doppler distortion.
>
>OK, now I see the problem. Frequency modulation doesn't
>require and, in fact, is independent of, non-linearity in
>the sense used here.
>
>FM sidebands are Bessel functions generated by expanding
>the right hand side of an expression that includes angular
>velocities and frequencies *only*. IOW, "linear".

Right. The whole system is completely linear (if you assume perfect
drivers and noncompressable air), and can be modelled in a linear
fashion.

The easiest way to do it is to take a coaxial speaker as your example.
You got two parts, first a way to determine the woofer excursion as
an instantaneous function of input signal, which is easy to do and
a matter of some simple box modelling, and secondly a way to take the
output of that and use it to modulate the tweeter signal. And that is
just a Bessel function. You should be able to knock this out in Matlab
in fairly short order.

Doing it with a full-range driver is harder because you can't easily
just draw a line and say below this point is modulating signal and
above this point is modulated.

But yes, I don't see any reason why we have to assume anything but a
linear model.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Carey Carlan]

Bob Cain > wrote in
:

> In the situation presented of a little speaker mounted on a
> big one, you will get Doppler distortion only if the big one
> is acoustically transparent. When it is acoustically rigid
> you have an entirely different situation and no Doppler
> distortion will occur.

That equates to saying that a train whistle moving toward you at 20 mph
will have no pitch shift if it's in a 20 mph tailwind.

Try again.

[Ben Bradley]

On Wed, 11 Aug 2004 14:18:01 -0700, Bob Cain
> wrote:

>
>
>Ben Bradley wrote:
>
>
>>
>> If you made a transducer that increases and decreases the air
>> pressure without using physical movement, there would be no doppler
>> distortion.
>
>Impossible on first principles of acoustics.

Doesn't a whistle do this, make sound without any movement of
anything but the air itself? Or are we talking past each other...

>Increasing and
>decreasing the air pressure results in totally predictable
>changes in the velocity of the air.

Right. See the second "pressure =" equation in the other post I
just posted...

>The are simply
>proportional through the (real) characteristic impedence of air.

Yes, if you detect it as I describe below.

>If the SPL is high enough, yes, nonlinearities occur in the
>air and the above isn't true but you have to get pretty
>darned high for that to have any signifigance. At the
>levels we listen to, air is highly linear.

Agreed, and I am assuming SPL levels that are not unusually high.

>My argument is simply that if you can reproduce velocity of
>air then by the above, the pressure has no choice but to
>remain in phase and proportional if it remains in the linear
>regime. If you can measure it you can reproduce it by
>moving a piston with the measured velocity. Exactly. The
>resulting pressure wave contains no distortion.

To measure it with no distortion, you would have to 'follow' the
pressure wave: (this is impractical except for the lowest frequencies,
it ignores the mass of the mic diaphragm [as well as the rest of the
mic!], and lots of other detailed problems, but bear with me) have a
mic mounted on a servo (such as a voice coil of a loudspeaker) that
moves the mic back when it senses an increase in pressure and forward
when it senses a decrease, so there is practically no change in the
pressure sensed by the mic diaphragm. The servo signal to move the mic
will reproduce the acoustic wave impressing on the mic.

>The above argument stands whether we are talking about
>reproducing pressure or velocity because in air they are in
>phase and proportional in a plane wave and deviations from
>planarity only have linear consequences.
>
>
>> And a heads up, "Porky" over there is quite similar in demeanor to
>> "Phil Allison" here on RAP.
>
>Actually, Porky has been nothing but congenial and careful
>of late. It was on that tentative basis that I chose to
>address his post.

Okay, I was obviously going on previous experience. Posts from AMHS
were nonexistent for a month or two (I can only imagine Bellsouth's
feed for AMHS dried up), then I all of a sudden saw them showing up
again in the last few days.

>Bob

-----
http://mindspring.com/~benbradley

[Chris Hornbeck]

On Wed, 11 Aug 2004 22:28:36 -0400, Ben Bradley
> wrote:

>>> If you made a transducer that increases and decreases the air
>>> pressure without using physical movement, there would be no doppler
>>> distortion.
>>
>>Impossible on first principles of acoustics.
>
> Doesn't a whistle do this, make sound without any movement of
>anything but the air itself? Or are we talking past each other...

Also the modulated arc "ion" speakers and the modulated flame
(I **** thee not) speakers used in Vietnam for propaganda flights.

The latter weren't high fi but were loud enough to allow you to
fly high enough to not be seen. A definite advantage given the
mood of the crowd.

Chris Hornbeck

[Chris Hornbeck]

On 11 Aug 2004 22:14:41 -0400, (Scott Dorsey) wrote:

> The whole system is completely linear (if you assume perfect
>drivers and noncompressable air), and can be modelled in a linear
>fashion.

One other assumption for "perfect" linearity is infinite bandwidth.
It's a given for our models, but I wonder how significant it may be
in the context of related questions of audibility.

Chris Hornbeck

[Bob Cain]

William Sommerwerck wrote:

>>It's really simple and even easy to understand. Doppler
>>shift is a phenomenon that occurs when a source is moving
>>with respect to the medium or _through_ the medium in which
>>it is generating a wave. In the case of a loudspeaker, or a
>>little one mounted on a big one, or whatever, it is not
>>moving with respect to the medium, it is moving the medium.
>> There is a fundamental difference.
>
>
> Interesting. (Sounds like one of my own posts.)
>
> Question: How does the air in front of the speaker "distinguish" between the
> cone moving back and forth, and the driver as a whole being moved back and forth
> (without any signal applied to the voice coil) at the same rate and amplitude?

I don't think a question of how it distinguishes is
meaninful. The physics is simply different if the generator
is moving within the medium or moving it.

Notice the difference I alluded to between a speaker just
moving back and forth in a medium by itself and mounted to
the face of a plane that is moving the same way and itself
generating a plane wave. Does it not seem logical that
there would be a difference?

I say that the difference is that when it is mounted on a
plane that is moving it just adds to the velocity/pressure
of the wave that is generated in a linear fashion and when
it is moving the same way by itself, without being part of a
larger generator, the result is "Doppler distortion" of
whatever it is generating. Thing is, though, that the
latter doesn't describe the physics of loudspeakers we use.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Carey Carlan wrote:

> Bob Cain > wrote in
> :
>
>
>>In the situation presented of a little speaker mounted on a
>>big one, you will get Doppler distortion only if the big one
>>is acoustically transparent. When it is acoustically rigid
>>you have an entirely different situation and no Doppler
>>distortion will occur.
>
>
> That equates to saying that a train whistle moving toward you at 20 mph
> will have no pitch shift if it's in a 20 mph tailwind.
>
> Try again.

Ok. If the whistle is moving at 20 miles an hour, and so is
the wind, and you are standing on the ground then the medium
is moving with respect to you. That's the same physics as
being on the moving train listening to a stationary whistle.
Doppler shift will result.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Chris Hornbeck]

On Thu, 12 Aug 2004 02:56:06 GMT, Chris Hornbeck
> wrote:

> I wonder how significant it may be
>in the context of related questions of audibility.

On second thought, this is irrelevant ("It's not irrelevant;
it's a hippopatamus!").

Note: you have to say the quote above with the cheesiest
possible faux Viennese accent.

Anyway, just ignore me; I'm an idiot.

Chris Hornbeck

[William Sommerwerck]

> One other assumption for "perfect" linearity is infinite bandwidth.
> It's a given for our models, but I wonder how significant it may be
> in the context of related questions of audibility.

Not so. Linearity and bandwidth are not related. To put it another way, lack of
infinite bandwidth is not considered "distortion."

[Chris Hornbeck]

On Wed, 11 Aug 2004 21:00:38 -0700, "William Sommerwerck"
> wrote:

>> One other assumption for "perfect" linearity is infinite bandwidth.
>> It's a given for our models, but I wonder how significant it may be
>> in the context of related questions of audibility.
>
>Not so. Linearity and bandwidth are not related. To put it another way, lack of
>infinite bandwidth is not considered "distortion."

For FM they're (only) related in the context of a complete
modulation and demodulation. That's a poor fit to the models
we're discussing. Best to just ignore my ravings.

OTOH.....

Nahhh...

Chris Hornbeck

[Bob Cain]

William Sommerwerck wrote:

>>>Question: How does the air in front of the speaker "distinguish" between the
>>>cone moving back and forth, and the driver as a whole being moved back and
>
> forth
>
>>>(without any signal applied to the voice coil) at the same rate and
>
> amplitude?
>
>
>>I don't think a question of how it distinguishes is
>>meaninful. The physics is simply different if the generator
>>is moving within the medium or moving it.
>
>
> That's the problem. There is no difference.

Ah, but there is.

>>Notice the difference I alluded to between a speaker just
>>moving back and forth in a medium by itself and mounted to
>>the face of a plane that is moving the same way and itself
>>generating a plane wave. Does it not seem logical that
>>there would be a difference?
>
>
> Nope, I'm afraid Newtonian Relativity says otherwise.

Hmmm, do you mean that these two quite different physical
systems are going to behave in the same way? Please explain
what Newtonial relativity says about these different systems
that makes them indistinguishable.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Phil Allison]

<Kurt Riemann>
"Arny Krueger"

>>It is this added velocity that causes the Doppler distortion.
>
Except that I disagree that there IS any velocity added to the higher
> wave. The wave IS velocity. No more, no less. Complex but coherent.
>

** The source of the wave has a velocity - you moron.

That alters the frequency in the air.

The wave velocity in air is fixed.



> Given the degree to which Doppler shift is a measurable phenomena
> regulated by the speed of sound in air, and is very auduble from
> objects traveling at relatively low velocities
>
> AND
>
> Given that a speaker moves at a high rate of speed,


** Nope - 1 m/S at most.

About 2 mph.


>
> Shouldn't doppler distortion be garishly apparent?


** No - you jerk off.


> If it is so subtle
> that it has escaped everyone's attention, it must be violating some of
> Doppler's own physical laws.


** False assertion - thence a false conclusion.


>
> Even a Sawtooth wave would theoretically show doppler distortion. Not
> only that, but if you were to take the harmonic components of a
> sawtooth wave and play them all out of phase with each other, there
> would be no difference in sound, but they would theoretically be
> modulating each other.


** Ignorant bull****.

Equates summing with multiplying.




>
> Anyway, I stand by my assertions.


** Where the lunatic stands is a place for others to instantly evacuate.




............. Phil

[Ben Bradley]

On Wed, 11 Aug 2004 21:45:56 -0700, Bob Cain
> wrote:

>
>
>William Sommerwerck wrote:
>
>>>>Question: How does the air in front of the speaker "distinguish" between the
>>>>cone moving back and forth, and the driver as a whole being moved back and
>>
>> forth
>>
>>>>(without any signal applied to the voice coil) at the same rate and
>>
>> amplitude?
>>
>>
>>>I don't think a question of how it distinguishes is
>>>meaninful. The physics is simply different if the generator
>>>is moving within the medium or moving it.

How so, Bob?

>> That's the problem. There is no difference.
>
>Ah, but there is.

Bob, what's the difference if the cone is moved by an electrically
supeimposed signal of two sine waves, and if it is moved electrically
by one sine wave and the whole speaker frame is moved mechanically by
another sine wave? Does the cone not go through the same motion in
both cases?

>>>Notice the difference I alluded to between a speaker just
>>>moving back and forth in a medium by itself and mounted to
>>>the face of a plane that is moving the same way and itself
>>>generating a plane wave. Does it not seem logical that
>>>there would be a difference?

The plane will have more surface area than the speaker cone, so the
plane would make a louder sound for the same depth of motion.

But if the speaker were emitting a high frequency signal, it would
be emitted on a surface that's moving back and forth at a lower
frequency to a large depth (whether it's just the cone or the driver
and plane), and it would be frequency-modulated just the same.

>>
>>
>> Nope, I'm afraid Newtonian Relativity says otherwise.
>
>Hmmm, do you mean that these two quite different physical
>systems are going to behave in the same way? Please explain
>what Newtonial relativity says about these different systems
>that makes them indistinguishable.
>
>
>Bob
>--
>
>"Things should be described as simply as possible, but no
>simpler."
>
> A. Einstein

-----
http://mindspring.com/~benbradley

[Kurt Riemann]

Haiku for my new newsgroup stalker
--------------------------------------------------------

I wake up each day
Happy and refreshed
For I am not Phil

A great stereo
must never be listened to
only analyzed

innacuracies
in all trivial matters
make his head explode

The burden of his knowledge
Drives him to lash out
oddly, at Rivers

no social graces
and yet he knows everything
alone in his cult

Australia is home
To Phil and the vast outback
Thank God for oceans

His perfect knowlege
Hidden in his dark replies
Never sees the point

His perfect newsgroup
Would be all Phil Allisons
All noise? Or silence?

His nasty retorts
drive away the questioners
Now he will be Plonked


----------------------------------------------------------

I am Kurt Riemann
No longer seeing that jerk
On my newsreader

[Arny Krueger]

"Bob Cain" > wrote in message


> Impossible on first principles of acoustics. Increasing and
> decreasing the air pressure results in totally predictable
> changes in the velocity of the air. The are simply
> proportional through the (real) characteristic impedence of air.

Can't air pressure be changed by thermal means?

[Arny Krueger]

<Kurt Riemann> wrote in message

> On Wed, 11 Aug 2004 21:51:48 -0400, "Arny Krueger" >
> wrote:
>
>
>>> Are you thinking the 50Hz is a modulator?
>>
>> Yes, the 50 Hz is the modulator.
>>
>>> It isn't moving identically to a pure 50Hz tone, it has 4k *mixed*
>>> in which means that the speaker changes it's excursion to represent
>>> the 4k tone.
>>
>> Agreed.
>>
>>> If there is no IM distortion, then the two waveforms merely
>>> follow the waveform.
>>
>> That's what the cone does. However you must look at the situation
>> from the viewpoint of the receiver/listener, not the viewpoint of
>> the cone.
>
> Interesting.
>
>>
>> The receiver/listener *sees* a 4 KHz source that is moving back and
>> forth in accordance with the 50 Hz sine wave. The position of the
>> cone as a function of time is correct at all times. However, the 4
>> KHz source is apparently moving from the viewpoint of the listener.
>> Therefore it is Doppler-shifted.

>>> It is not "pushing" the waves of the 4k tone.

>> No, but it is moving he source of the 4 KHz tone.

> It is here where great minds disagree.

Disagreement can be good.

>> The position of the cone is analogous to the amplitude of the cone.
>> The position of the cone is correct, so there is no amplitude
>> distortion and no amplitude distortion. However, when the cone
>> correctly follows the electrical energy applied to it, the cone
>> moves a 4 KHz acoustical source (itself) back and forth with respect
>> to the receiver/listener at a 50 Hz rate. It is this added velocity
>> that causes the Doppler distortion.

> Except that I disagree that there IS any velocity added to the higher
> wave. The wave IS velocity. No more, no less. Complex but coherent.

You're right, there is no velocity added to the wave in the air. It moves at
the same speed as any other sound. It's the source that picks up the added
velocity.

> Given the degree to which Doppler shift is a measurable phenomena
> regulated by the speed of sound in air, and is very auduble from
> objects traveling at relatively low velocities

AND

> Given that a speaker moves at a high rate of speed,

> Shouldn't doppler distortion be garishly apparent?

Depends on the situation.

I don't think that a speaker cone motion due to bass is really all that
fast. A woofer cone operating at 50 Hz will move at a peak speed of about
314 inches per second, or about 27 feet per second. This is only about 2% of
the speed of sound.

> If it is so subtle that it has escaped everyone's attention, it must be
violating some of
> Doppler's own physical laws.

Doppler has not escaped the attention of the technical community. There are
a number of JAES papers about it. Audio Glossaries on the web contain
up-to-date information about it. Thing is, Doppler is a relatively simple
thing, and the issue is thought to be more-or-less settled within learned
circles. I think the last paper I found about it in the JAES archive was
from the early 1980s.

> Even a Sawtooth wave would theoretically show doppler distortion.

Yes.

> Not only that, but if you were to take the harmonic components of a
> sawtooth wave and play them all out of phase with each other, there
> would be no difference in sound, but they would theoretically be
> modulating each other.

I don't know about the "no difference in sound" in every case. What we have
learned is that Doppler FM distortion always seems to create artifacts that
in reasonable worst case real-world speakers, are always submerged in AM
effects. Perhaps when we reduce AM effects by an order of magnitude, we'll
have to look more seriously at Doppler-related effects.

[Arny Krueger]

"Phil Allison" > wrote in message



>> Given that a speaker moves at a high rate of speed,

> ** Nope - 1 m/S at most.

> About 2 mph.

Do the math Phil. The largest stroke woofers around have about 2" linear
stroke which can happen at 50 Hz. The frequency at which the maximum stroke
can be achieved is limited, because the woofer becomes heavily mass-loaded
at higher frequencies, but 50 Hz can be below that frequency for woofers
like these.

50*2*pi*2 = 628 ips = about 50 fps = a peak cone velocity about 15 m/S

In my other example, I used 1" stroke, and still came up with 27 FPS or
about 8 m/S

In fact there are commercial woofers with a lot more than 25.6 mm Xmax, and
some of them can go a bit higher than 50Hz without becoming so mass-loaded
that they can't do their full linear stroke. Speaker cones can also
sometimes substantially exceed their Xmax.

Bottom line Phil, you're off by about an order of magnitude on maximum cone
velocity. But your heart is in the right place - these aren't what could be
reasonably called "a high rate of speed".

[Arny Krueger]

"philicorda" > wrote in message
rg
> On Wed, 11 Aug 2004 16:21:24 -0700, William Sommerwerck wrote:
>
>>> Example 2:
>>
>>> I generate a 4 KHz tone and a 50Hz tone. I sum them, and feed them
>>> to a full-range speaker through an amplifier with low IM
>>> distortion. From the speaker, I hear 4KHz and 50Hz. No vibrato,
>>> because the speaker is accurately reproducing the waveform that is
>>> the sum of the two tones. No Doppler distortion.
>>
>> Well... No. The 4kHz signal is being reproduced from a source that
>> is moving with respect to the listener.
>
> Say I have a diaphram like a bass drum, and hit it, surely the same
> thing is going on (tones at higher multiple frquencies+the skin
> moving slowly at the fundamental pitch).

I believe so.

> So, would a speaker cone not have to do the same thing to reproduce it?

Remember, that a speaker does not reproduce the motion of a drum diaphragm,
it reproduces that which was picked up by a microphone that was in the
sound field of the drum. Your example would be more valid if we were in the
habit of putting transducers on bass drum diaphragms.

> Is there 'doppler distortion' on acoustic instruments?

So it would seem.

> Could the same thing be said about microphone diaphrams? By picking
> up a low frequency and high frequency sound at the same time, would
> the same effect not apply?

So it would seem. However, in the case of mics the motion of the diaphragm
is so small that its Doppler distoriton is really small.

> Sorry for all the questions. :)

Well, the big lesson is that in the current context, Doppler FM distortion
is submerged by the large amounts of AM distortion in speakers.

[Arny Krueger]

"William Sommerwerck" > wrote in message

>> One other assumption for "perfect" linearity is infinite bandwidth.
>> It's a given for our models, but I wonder how significant it may be
>> in the context of related questions of audibility.
>
> Not so. Linearity and bandwidth are not related. To put it another
> way, lack of infinite bandwidth is not considered "distortion."

Agreed. However, the phrase "Linear Distortion" applies to things like lack
of bandwidth.

[Arny Krueger]

"Chris Hornbeck" > wrote in message

> On Wed, 11 Aug 2004 18:26:42 -0700, "William Sommerwerck"
> > wrote:
>
>> Question: How does the air in front of the speaker "distinguish"
>> between the cone moving back and forth, and the driver as a whole
>> being moved back and forth (without any signal applied to the voice
>> coil) at the same rate and amplitude?

> Exactly right. This can be restated as "air is very low impedance".
> Conventional speakers operate into something close to a short
> circuit.

I don't think so. Speakers are suspension and/or enclosure air compliance
loaded below resonance. They usually become cone mass-loaded around and
above resonance.

Loudspeaker horns are acoustical transformers that match the high compliance
of the air to the relatively low source impedance of most conventional
loudspeaker drivers.

Horn-loaded drivers are the only ones that operate into an acoustical
impedance low enough to be called anything like a matched impedance, and it
still isn't anything like an acoustical short.

A driver operating into an acoustical short circuit would be motionless.

[Arny Krueger]

"Ben Bradley" > wrote in message


> Bob, what's the difference if the cone is moved by an electrically
> supeimposed signal of two sine waves, and if it is moved electrically
> by one sine wave and the whole speaker frame is moved mechanically by
> another sine wave? Does the cone not go through the same motion in
> both cases?

Good point.

[Arny Krueger]

"Chris Hornbeck" > wrote in message

> On Wed, 11 Aug 2004 18:08:28 -0700, Bob Cain
> > wrote:
>
>> Doppler
>> shift is a phenomenon that occurs when a source is moving
>> with respect to the medium or _through_ the medium in which
>> it is generating a wave. In the case of a loudspeaker, or a
>> little one mounted on a big one, or whatever, it is not
>> moving with respect to the medium, it is moving the medium.
>> There is a fundamental difference.
>
> I see two flaws here. First is that the FM exists *at the
> diaphragm* and is independent of media.

The FM exists at the receiver or listener. If the speaker and the listener
have no relative velocity, no Doppler.

People who ride on trains don't hear the whistle of their train as being
Doppler-shifted. Been there, done that.

> Second and lesser is in a way just a restatement of the
> observation that conventional diaphragms are high impedance
> and air is low impedance. Low acoustic impedance drivers
> exhibit low FM distortions (by definition, in this
> backwards description).

Agreed.

> At some point here we're going to need to talk about horns,
> but I'm dreading it. Folk get all riled up.

Sad too, its really pretty simple - a horn is an acoustical impedance
matching transformer.

[Arny Krueger]

"Bob Cain" > wrote in message

> Arny Krueger wrote:
>
>
>>> Arny, when you start mixing distributed non-linearities such
>>> as that in the surround, that of cone distortion, that of
>>> the magnetic circuit, etc. It is not generally possible to
>>> describe the resulting form of distortion.

>> What, whether it is AM or FM or what proportion of which?

> Whether it is even formally describable.

It's formally describable!

>> Sources don't matter, all that matter is a clean enough signal to
>> analyze.

> The hell they don't. If what is generating the data to be
> measured cannot be characterized then neither can the data.

Well, all we need to know is "This is the sound that is coming out of the
front of the speaker".

>> Lets go down your list:
>
>> (1) that in the surround - doesn't matter where the Doppler comes
>> from, just that it is.

> I don't follow this.

What does a speaker do? It makes sound. What do we do with speakers? We put
them in boxes. To make things simple let's consider a sealed box. The sealed
box is there to ensure that the only sound we hear comes out of the front of
the speaker, not its back. Therefore, all we need to do is characterize the
sound that is coming out of the front of the speaker.

>> (2) that of cone distortion - doesn't matter where the Doppler comes
>> from, just that it is.'

> This either.

Same story. All we need to do is characterize the sound coming out of the
front of the speaker, regardles of its source.

>> (3) the magnetic circuit - not moving, so it can't cause Doppler

> I understand this one. The question remains whether FM can
> be ruled out of an active system that has these forms of
> distortion in a distributed and interacting fashion. Can it?

The general case is that there is both AM & FM distortion. The purpose of
the measurement is to determine where or not there is FM distortion.

>>> In fact, when I simulated a simple model of the described
>>> effect, the distortion produced was chaotic and broadband,
>>> not isolated spectral lines.
>>
>>
>> We get pretty clean isolated spectral lines from real-world
>> measurements. Guess what that says about the simulation?

> What's it say about the system under test?

It's performing a lot different than the simulation that predicts chaos.

> What does it specifically say about Doppler distortion?

Our test finds some Doppler distortion.


>> We don't need a working theory to have believable experimental
>> results.

> Absolutely agreed, but to have a believable experimental
> result all factors that can contribute to the data in the
> same way that the phenomenon being investigated can must
> either be completely characterized or eliminated. This is
> fundamental.

It's not a problem here because we do have a working, believeable theory
about loudspeaker Doppler.

[Arny Krueger]

"Phil Allison" > wrote in message

> "Bob Cain"
>>
>> I've got an argument that so far has withstood some scrutiny
>> which shows that Doppler distortion in a myth.
>>
>
>
> ** This article has all the maths re the Doppler effect in woofers.
>
> http://www.geocities.com/kreskovs/Doppler1.html

I still haven't reviewed it thoroughly, but it looks a lot like some of the
JAES papers I've cited recently.

But, he blew the experiment, because his results could be and probably are
dominated by AM effects.

The expeirment part of the article was deconstructed last week in that other
forum you participate in, Phil. Forgot?

[philicorda]

On Wed, 11 Aug 2004 16:21:24 -0700, William Sommerwerck wrote:

>> Example 2:
>
>> I generate a 4 KHz tone and a 50Hz tone. I sum them, and feed them to
>> a full-range speaker through an amplifier with low IM distortion. From
>> the speaker, I hear 4KHz and 50Hz. No vibrato, because the speaker is
>> accurately reproducing the waveform that is the sum of the two tones.
>> No Doppler distortion.
>
> Well... No. The 4kHz signal is being reproduced from a source that is moving
> with respect to the listener.

Say I have a diaphram like a bass drum, and hit it, surely the same thing
is going on (tones at higher multiple frquencies+the skin moving slowly at
the fundamental pitch).

So, would a speaker cone not have to do the same thing to reproduce it?
Is there 'doppler distortion' on acoustic instruments?
Could the same thing be said about microphone diaphrams? By picking up a
low frequency and high frequency sound at the same time, would the same
effect not apply?

Sorry for all the questions. :)

[Phil Allison]

"Arny Krueger"
> "Phil Allison"
>
> >> Given that a speaker moves at a high rate of speed,
>
> > ** Nope - 1 m/S at most.
>
> > About 2 mph.
>
> Do the math Phil.


** Go pull your tiny dick - Arny.


> The largest stroke woofers around have about 2" linear
> stroke which can happen at 50 Hz.


** The OP mentioned simply "speaker" - not sub woofer.

You come back with an excursion number for the most extreme sub woofer that
exists.

Subs are not used to produce frequencies in the kHz range.


>
> 50*2*pi*2 = 628 ips = about 50 fps = a peak cone velocity about 15 m/S
>


** WRONG: V = 2*pi*f * X-max.


> In my other example, I used 1" stroke, and still came up with 27 FPS or
> about 8 m/S
>

** WRONG.


> Bottom line Phil, you're off by about an order of magnitude on maximum
cone
> velocity.


** But I was talking of a "speaker" - just as the OP was.

Speakers have an X-max of about 6mm which is reached at about 30 Hz.

2*pi*.006*30 = 1.13 m/S




.............. Phil

[Arny Krueger]

"Phil Allison" > wrote in message

> "Arny Krueger"
>> "Phil Allison"
>>
>>>> Given that a speaker moves at a high rate of speed,

>>> ** Nope - 1 m/S at most.

>>> About 2 mph.

>> Do the math Phil.

> ** Go pull your tiny dick - Arny.

How do you know what size it is, Phil? Been fantasizing about me? ;-)

>> The largest stroke woofers around have about 2" linear
>> stroke which can happen at 50 Hz.

> ** The OP mentioned simply "speaker" - not sub woofer.

Oh Phil are you saying that subwoofers aren't speakers?

> You come back with an excursion number for the most extreme sub
> woofer that exists.

No, that one has Xmax that is about 40% more than 1" - about 36 mm if I
recollect properly. I was giving you a break!

> Subs are not used to produce frequencies in the kHz range.

Agreed, but due to their long stroke, some people think they might be
candidates for Doppler distortion.

>> 50*2*pi*2 = 628 ips = about 50 fps = a peak cone velocity about 15
>> m/S

> ** WRONG: V = 2*pi*f * X-max.

Agreed, so now we're back to my original example of about 7 m/S


>> Bottom line Phil, you're off by about an order of magnitude on
>> maximum cone velocity.

> ** But I was talking of a "speaker" - just as the OP was.

Phi,l are you saying that subwoofers aren't speakers?

> Speakers have an X-max of about 6mm which is reached at about 30 Hz.

Phil, are you saying that subwoofers aren't speakers?

> 2*pi*.006*30 = 1.13 m/S

But to quote you Phil,

"Nope - 1 m/S at most."

Phil, even your example, as limited as it is, is > 1 m/S

[Phil Allison]

"Arny Krueger"
> "Phil Allison"
> > "Bob Cain"
> >>
> >> I've got an argument that so far has withstood some scrutiny
> >> which shows that Doppler distortion in a myth.
> >>
> >
> > ** This article has all the maths re the Doppler effect in woofers.
> >
> > http://www.geocities.com/kreskovs/Doppler1.html


> I still haven't reviewed it thoroughly, but it looks a lot like some of
the
> JAES papers I've cited recently.
>
> But, he blew the experiment, because his results could be and probably are
> dominated by AM effects.


** Kindly point to the "experiment" data in the article ??



> The expeirment part of the article was deconstructed last week in that
other
> forum you participate in, Phil. Forgot?


** Kindly point to the particular NG and thread ???

You are using several of the debating cheats from my list again -
Arny.



............. Phil

[Arny Krueger]

"Phil Allison" > wrote in message

> "Arny Krueger"
>> "Phil Allison"
>>> "Bob Cain"
>>>>
>>>> I've got an argument that so far has withstood some scrutiny
>>>> which shows that Doppler distortion in a myth.
>>>>
>>>
>>> ** This article has all the maths re the Doppler effect in woofers.
>>>
>>> http://www.geocities.com/kreskovs/Doppler1.html
>
>
>> I still haven't reviewed it thoroughly, but it looks a lot like some
>> of the JAES papers I've cited recently.
>>
>> But, he blew the experiment, because his results could be and
>> probably are dominated by AM effects.

> ** Kindly point to the "experiment" data in the article ??

The exact page you cited Phil has this text and a hyperlink: "On the next
page I present experimental data supporting the results predicted by the
analysis."

The hyperlink goes to:

http://www.geocities.com/kreskovs/Doppler2.html

You must really be losing it, Phil!

>> The experiment part of the article was deconstructed last week in
>> that other forum you participate in, Phil. Forgot?

> ** Kindly point to the particular NG and thread ???

http://groups.google.com/groups?selm=ssOdnd1Rdv5sBpLcRVn-sA%40comcast.com

I looked a little closer and found that you didn't participate in that
thread, Phil. Your participation in that group may be unintentional -
crossposts.

> You are using several of the debating cheats from my list again
> - Arny.

Just because something can be used as a cheat, doesn't mean that every use
of it is a cheat.

[Phil Allison]

"Arny Krueger"
> "Phil Allison" <
> >>>
> >>> ** This article has all the maths re the Doppler effect in woofers.
> >>>
> >>> http://www.geocities.com/kreskovs/Doppler1.html
> >
> >
> >> I still haven't reviewed it thoroughly, but it looks a lot like some
> >> of the JAES papers I've cited recently.
> >>
> >> But, he blew the experiment, because his results could be and
> >> probably are dominated by AM effects.
>
> > ** Kindly point to the "experiment" data in the article ??
>
> The exact page you cited Phil has this text and a hyperlink: "On the next
> page I present experimental data supporting the results predicted by the
> analysis."
>
> The hyperlink goes to:
>
> http://www.geocities.com/kreskovs/Doppler2.html
>
> You must really be losing it, Phil!


** There is no hyperlink on any of the 18 pages of the article I gave the
URL for - I simply missed the one on the synopsis page. That test data is
*indeed* pathetic.

I have grave doubts now that anything in that article is actually true.

BUT it does contain the math that allegedly supports loudspeaker Doppler -
as I stated.



> > You are using several of the debating cheats from my list again
> > - Arny.

>
> Just because something can be used as a cheat, doesn't mean that every use
> of it is a cheat.


** Another debating fallacy - arguing for the general to the
particular.




.......... Phil

[William Sommerwerck]

>> Impossible on first principles of acoustics. Increasing and
>> decreasing the air pressure results in totally predictable
>> changes in the velocity of the air. The are simply
>> proportional through the (real) characteristic impedence of air.

> Can't air pressure be changed by thermal means?

Yes. That's how plasma speakers work. (I heard this straight from the mouth of
Dr. Allen Hill.)

[William Sommerwerck]

> Bob, what's the difference if the cone is moved by an electrically
> supeimposed signal of two sine waves, and if it is moved electrically
> by one sine wave and the whole speaker frame is moved mechanically
> by another sine wave? Does the cone not go through the same motion
> in both cases?

Bingo. We have now, as Dr. Land would point out, asked the right question.

[Arny Krueger]

"William Sommerwerck" > wrote in message

>>> Impossible on first principles of acoustics. Increasing and
>>> decreasing the air pressure results in totally predictable
>>> changes in the velocity of the air. The are simply
>>> proportional through the (real) characteristic impedence of air.
>
>> Can't air pressure be changed by thermal means?
>
> Yes. That's how plasma speakers work. (I heard this straight from the
> mouth of Dr. Allen Hill.)

I guess I can then say that I've heard the thermal principle working,
straight from the mouths of a set of Plasmatronics speakers. ;-)

[Arny Krueger]

"Phil Allison" > wrote in message

> "Arny Krueger"
>> "Phil Allison" <
>>>>>
>>>>> ** This article has all the maths re the Doppler effect in
>>>>> woofers.
>>>>>
>>>>> http://www.geocities.com/kreskovs/Doppler1.html
>>>
>>>
>>>> I still haven't reviewed it thoroughly, but it looks a lot like
>>>> some of the JAES papers I've cited recently.
>>>>
>>>> But, he blew the experiment, because his results could be and
>>>> probably are dominated by AM effects.
>>
>>> ** Kindly point to the "experiment" data in the article ??
>>
>> The exact page you cited Phil has this text and a hyperlink: "On the
>> next page I present experimental data supporting the results
>> predicted by the analysis."
>>
>> The hyperlink goes to:
>>
>> http://www.geocities.com/kreskovs/Doppler2.html
>>
>> You must really be losing it, Phil!

> ** There is no hyperlink on any of the 18 pages of the article I
> gave the URL for - I simply missed the one on the synopsis page.

Hidden in plain sight, as it were!

> That test data is *indeed* pathetic.

Thanks for agreeing.

> I have grave doubts now that anything in that article is actually true.

Like I said before - it needs comparison with the relevant JAES papers.

> BUT it does contain the math that allegedly supports loudspeaker
> Doppler - as I stated.

No doubt.

>>> You are using several of the debating cheats from my list again
>>> - Arny.

>> Just because something can be used as a cheat, doesn't mean that
>> every use of it is a cheat.

> ** Another debating fallacy - arguing for the general to the
particular.

....and back at you, Phil.

The point you keep missing Phil, is that just because something is not an
airtight fact or based on indisputable logic, doesn't mean that there's not
some relevant truth somewhere near it. I find that obtaining truth is often
an interative process.

[Phil Allison]

"Bob Cain"

>
> Ok. If the whistle is moving at 20 miles an hour, and so is
> the wind, and you are standing on the ground then the medium
> is moving with respect to you. That's the same physics as
> being on the moving train listening to a stationary whistle.
> Doppler shift will result.



** If I read you correctly Bob:


1. The air volume in close proximity to the cone of a woofer performing low
frequency excursions moves with it as a whole - so they have essentially
the same velocity at all times.

2. That means there is no effective cone / air velocity differential as is
required to create the Doppler effect in air from the cone simultaneously
vibrating at some high frequency.

Is it as simple as that ?

If so, you have a very nice point.




................ Phil

[Phil Allison]

"Arny Krueger"
> "Phil Allison" <
>
> The point you keep missing Phil, is that just because something is not an
> airtight fact or based on indisputable logic, doesn't mean that there's
not
> some relevant truth somewhere near it.


** So says every audiophool - Arny.

There is an infinite number of things that are not quite true.

There are only a precious few that are.


> I find that obtaining truth is often an interative process.


** You have demonstrated no idea how to find out the truth.

Mainly by arrogantly ****ing on those who already know what you do not.



............. Phil

[Arny Krueger]

"Bob Cain" > wrote in message


> Ok. If the whistle is moving at 20 miles an hour, and so is
> the wind, and you are standing on the ground then the medium
> is moving with respect to you. That's the same physics as
> being on the moving train listening to a stationary whistle.
> Doppler shift will result.

Also true, with no wind. The relevant variable is the relative motion
between the source and the receiver.

[Arny Krueger]

"Phil Allison" > wrote in message


> ** You have demonstrated no idea how to find out the truth.
>
> Mainly by arrogantly ****ing on those who already know what you do
> not.

If irony killed we'd all be dead!

[William Sommerwerck]

> The point you keep missing Phil, is that just because something
> is not an airtight fact or based on indisputable logic, doesn't mean
> that there's not some relevant truth somewhere near it. I find that
> obtaining truth is often an iterative process.

I'm biting my tongue...

[Phil Allison]

"Arny Krueger"
> "Phil Allison"
>>
> > ** You have demonstrated no idea how to find out the truth.
> >
> > Mainly by arrogantly ****ing on those who already know what you do
> > not.
>
> If irony killed we'd all be dead!


** No case in sight ......

So no case to answer.



............ Phil

[Phil Allison]

"William Sommerwerck"

Arny Kruegar:

> > The point you keep missing Phil, is that just because something
> > is not an airtight fact or based on indisputable logic, doesn't mean
> > that there's not some relevant truth somewhere near it. I find that
> > obtaining truth is often an iterative process.
>
> I'm biting my tongue...


** So you should.

When Arny is blowing it out his arse we all should stand well back.



.............. Phil

[Scott Dorsey]

In article >,
Chris Hornbeck > wrote:
>On Thu, 12 Aug 2004 02:56:06 GMT, Chris Hornbeck
> wrote:
>
>> I wonder how significant it may be
>>in the context of related questions of audibility.
>
>On second thought, this is irrelevant ("It's not irrelevant;
>it's a hippopatamus!").
>
>Note: you have to say the quote above with the cheesiest
>possible faux Viennese accent.

No, Chico did it originally with a cheesy Italian accent.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Chris Hornbeck]

On Thu, 12 Aug 2004 07:12:30 -0400, "Arny Krueger" >
wrote:

>> This can be restated as "air is very low impedance".
>> Conventional speakers operate into something close to a short
>> circuit.
>
>I don't think so. Speakers are suspension and/or enclosure air compliance
>loaded below resonance. They usually become cone mass-loaded around and
>above resonance.

Within their passband conventional drivers contribute most of the
moving mass to the total mass (driver plus air) of the moving system.
And they are capable of exerting much greater force than can be
"used" by the high compliance of ambient air.

But because they're small compared to a wavelength, conventional
drivers have trouble imparting much particle velocity to air.
They slosh around in it, all fury and little sound, signifying
nothing.

The high force to velocity ratio describes a high mechanical
impedance compared to air. Conventional drivers are muscle-bound.

>A driver operating into an acoustical short circuit would be motionless.

Actually a conventional driver would move very similarly in a vacuum.
I think; never tried it.

Chris Hornbeck

[Goofball_star_dot_etal]

On Thu, 12 Aug 2004 23:09:49 +1000, "Phil Allison"
> wrote:

>
>"Bob Cain"
>
>>
>> Ok. If the whistle is moving at 20 miles an hour, and so is
>> the wind, and you are standing on the ground then the medium
>> is moving with respect to you. That's the same physics as
>> being on the moving train listening to a stationary whistle.
>> Doppler shift will result.
>
>
>
> ** If I read you correctly Bob:
>
>
>1. The air volume in close proximity to the cone of a woofer performing low
>frequency excursions moves with it as a whole - so they have essentially
>the same velocity at all times.
>
>2. That means there is no effective cone / air velocity differential as is
>required to create the Doppler effect in air from the cone simultaneously
>vibrating at some high frequency.
>
> Is it as simple as that ?
>
> If so, you have a very nice point.
>

Yes, but only for about a second.

The distance between the transmitter and reciever is still being
changed. If you consider two positions of the speaker cone, A ="in" ,
B="out" and a microphone at C. It basically does not matter what the
speed of air or sound,or the path is between A and C since it is also
common to B to C apart from the bit ( A to B ). Sound from B arrives
before sound from A since it is nearer to C so there is a phase
displacement which is being modulated at 50Hz and it is simply equal
to the displacement of the speaker cone converted by frequency and
speed of sound, to an angular displacement of the cone.= (cone
displacement /wavelength@50Hz ) * 2 * PI radians.The linear
displacement is converted to phase modulation and therefore frequency
modulation.

[William Sommerwerck]

>> On second thought, this is irrelevant ("It's not irrelevant;
>> it's a hippopatamus!").
>> Note: you have to say the quote above with the cheesiest
>> possible faux-Viennese accent.

"Some say the title of this song is irrelevant. But it's not irrelevant -- it's
a hippopotamus!"

"Mud, mud, glorious mud.
Sling as much as you like -- it'll stir up the blood!"

[Scott Dorsey]

Chris Hornbeck > wrote:
>
>Also the modulated arc "ion" speakers and the modulated flame
>(I **** thee not) speakers used in Vietnam for propaganda flights.
>
>The latter weren't high fi but were loud enough to allow you to
>fly high enough to not be seen. A definite advantage given the
>mood of the crowd.

You got a cite on this, or even the name of a manufacturer? I know some
aircraft guys who would be very interested in this.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Chris Hornbeck]

On 12 Aug 2004 11:05:42 -0400, (Scott Dorsey) wrote:

>You got a cite on this, or even the name of a manufacturer? I know some
>aircraft guys who would be very interested in this.

Sorry, no. Pictures I've seen looked very
much like the double-bent-horn paging speakers, only much
bigger. They talked about 140 dB SPL or so, IIRC.

I kinda remember they modulated with a solenoid operated
valve in the fuel line. But my memory is notoriously
flakey.

Chris Hornbeck

[Chris Hornbeck]

On Thu, 12 Aug 2004 07:56:54 -0700, "William Sommerwerck"
> wrote:

>"Some say the title of this song is irrelevant. But it's not irrelevant -- it's
>a hippopotamus!"
>
>"Mud, mud, glorious mud.
>Sling as much as you like -- it'll stir up the blood!"

"His inamorata,
Adjusted her garter,"

But I didn't know they were quoting Chico! Thanks, Scott.

Chris Hornbeck

[Scott Dorsey]

Chris Hornbeck > wrote:
>
>But I didn't know they were quoting Chico! Thanks, Scott.

Chico: Judge, what's a gotta four legs and a trunk?

Groucho: That's irrelevant!

Chico: That's a right!
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[William Sommerwerck]

> Also the modulated-arc "ion" speakers and the modulated flame
> (I **** thee not) speakers used in Vietnam for propaganda flights.

Flame speakers actually date to the late 19th century. They worked, but were
noisy.

There have been several ionic speakers, most notably the DuKane Ionovac tweeter,
and the Hill Plasmatronic speaker, which was ionic from 700Hz up.

[William Sommerwerck]

> "His inamorata,
> Adjusted her garter,"

> But I didn't know they were quoting Chico!

They weren't.

[Chris Hornbeck]

On Thu, 12 Aug 2004 07:16:34 -0400, "Arny Krueger" >
wrote:

>> I see two flaws here. First is that the FM exists *at the
>> diaphragm* and is independent of media.
>
>The FM exists at the receiver or listener. If the speaker and the listener
>have no relative velocity, no Doppler.
>
>People who ride on trains don't hear the whistle of their train as being
>Doppler-shifted.

You raise a very interesting point and I'm not smart enough to
figure it out myself.

Suppose the listener were mounted on a (very strong) diaphragm
driven by the same signal, EQ'ed and time-delayed, as the source
diaphragm, in order to cancel out their relative movement.

Would the listener still hear the FM sidebands?

Chris Hornbeck

[Bob Cain]

Arny Krueger wrote:

> "Bob Cain" > wrote in message
>
>
>>Arny Krueger wrote:
>>
>>
>>
>>>>Arny, when you start mixing distributed non-linearities such
>>>>as that in the surround, that of cone distortion, that of
>>>>the magnetic circuit, etc. It is not generally possible to
>>>>describe the resulting form of distortion.
>
>
>>>What, whether it is AM or FM or what proportion of which?
>
>
>>Whether it is even formally describable.
>
>
> It's formally describable!

I don't mean whether simple FM is describable but whether
the net effect of all the interacting sources of distortion
in a loudspeaker is describable in order to know whether
they might be doing some FM on the way to the piston or
through it before the force gets to the piston/air
interface. If there is I'd love to see it.

>>The hell they don't. If what is generating the data to be
>>measured cannot be characterized then neither can the data.
>
>
> Well, all we need to know is "This is the sound that is coming out of the
> front of the speaker".

If all you are doing is measuring it. If you wish to draw
any conclusions about what made it that way then you need a
whole lot more than just measurement, unless the conclusions
are of the broadest nature. For example, "the thing
distorts." What if the effect you are looking for was
actually contained, for some reason and to some degree, in
the input, driving signal? Does that not need to be
accounted for?

>
>
>>>Lets go down your list:
>>
>>>(1) that in the surround - doesn't matter where the Doppler comes
>>>from, just that it is.
>
>
>>I don't follow this.
>
>
> What does a speaker do? It makes sound. What do we do with speakers? We put
> them in boxes. To make things simple let's consider a sealed box. The sealed
> box is there to ensure that the only sound we hear comes out of the front of
> the speaker, not its back. Therefore, all we need to do is characterize the
> sound that is coming out of the front of the speaker.

Unless one is trying to disect that to see what is doing
what to arrive at the result.

>
>
>>>(2) that of cone distortion - doesn't matter where the Doppler comes
>>>from, just that it is.'
>
>
>>This either.
>
>
> Same story. All we need to do is characterize the sound coming out of the
> front of the speaker, regardles of its source.

Ya know, Arny I really have a hard time beliving that you as
an experimentalist are really this naive. All I'm doing in
this sub-thread is describing the fundamentals of scientific
investigation and I shouldn't need to do that.

>
>
>>>(3) the magnetic circuit - not moving, so it can't cause Doppler
>
>
>>I understand this one. The question remains whether FM can
>>be ruled out of an active system that has these forms of
>>distortion in a distributed and interacting fashion. Can it?
>
>
> The general case is that there is both AM & FM distortion. The purpose of
> the measurement is to determine where or not there is FM distortion.

The purpose, for this discussion at least, is to determine
if it's due to "Doppler distortion" or can be accounted for
by the intrinsic distortion within the driver itself.

>>>We get pretty clean isolated spectral lines from real-world
>>>measurements. Guess what that says about the simulation?
>
>
>>What's it say about the system under test?
>
>
> It's performing a lot different than the simulation that predicts chaos.

Exactly. Show me a model that can be physically related to
what is supposedly happening that doesn't.

>>What does it specifically say about Doppler distortion?
>
>
> Our test finds some Doppler distortion.

How do you know it is "Doppler distortion" all you know is
that you seem to be seeing evidence of frequency modulation.

>>>We don't need a working theory to have believable experimental
>>>results.
>
>
>>Absolutely agreed, but to have a believable experimental
>>result all factors that can contribute to the data in the
>>same way that the phenomenon being investigated can must
>>either be completely characterized or eliminated. This is
>>fundamental.
>
>
> It's not a problem here because we do have a working, believeable theory
> about loudspeaker Doppler.

It's a problem here precisely because we don't have that
theory (and should by now.) There is nothing to compare
experiment against and no attention given to isolating the
effect under investigation so that we even could.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Kurt Riemann wrote:


>
> Except that I disagree that there IS any velocity added to the higher
> wave. The wave IS velocity. No more, no less. Complex but coherent.

Exactly, precisely and completely.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Arny Krueger wrote:


> Doppler has not escaped the attention of the technical community. There are
> a number of JAES papers about it.

Citations, please.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Ben Bradley wrote:


>>>
>>>>I don't think a question of how it distinguishes is
>>>>meaninful. The physics is simply different if the generator
>>>>is moving within the medium or moving it.
>
>
> How so, Bob?

By inspection. They are obviously different physical
situations. It remains to be shown that they are equivalent
in any sense and I think that's because it isn't possible.

>
>
>>>That's the problem. There is no difference.
>>
>>Ah, but there is.
>
>
> Bob, what's the difference if the cone is moved by an electrically
> supeimposed signal of two sine waves, and if it is moved electrically
> by one sine wave and the whole speaker frame is moved mechanically by
> another sine wave? Does the cone not go through the same motion in
> both cases?

Gotta chew on this one and on the rest of your challenge.
It's a darned good one and I don't wanna just jerk my knee
or wave my hands.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:

>>Bob, what's the difference if the cone is moved by an electrically
>>supeimposed signal of two sine waves, and if it is moved electrically
>>by one sine wave and the whole speaker frame is moved mechanically
>>by another sine wave? Does the cone not go through the same motion
>>in both cases?
>
>
> Bingo. We have now, as Dr. Land would point out, asked the right question.

Agreed, I think. :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:

>
> ** If I read you correctly Bob:
>
>
> 1. The air volume in close proximity to the cone of a woofer performing low
> frequency excursions moves with it as a whole - so they have essentially
> the same velocity at all times.
>
> 2. That means there is no effective cone / air velocity differential as is
> required to create the Doppler effect in air from the cone simultaneously
> vibrating at some high frequency.
>
> Is it as simple as that ?

Yes, I think. Without pondering it deeply, it seems to be
an accurate, yet different, way to state it and at least
tentatively I think they are equivalent.

How's that for a noncomittal affirmative? :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Logan Shaw]

Bob Cain wrote:
> Phil Allison wrote:

>> 1. The air volume in close proximity to the cone of a woofer
>> performing low
>> frequency excursions moves with it as a whole - so they have essentially
>> the same velocity at all times.
>>
>> 2. That means there is no effective cone / air velocity differential
>> as is
>> required to create the Doppler effect in air from the cone simultaneously
>> vibrating at some high frequency.
>>
>> Is it as simple as that ?

> Yes, I think. Without pondering it deeply, it seems to be an accurate,
> yet different, way to state it and at least tentatively I think they are
> equivalent.

Hmm, OK, I haven't been closely following the discussion, but if the air
at any distance[1] from the cone is always moving at absolutely the same
velocity as the cone, then that would imply that the sound wave propagates
at infinite speed[2], i.e. that the speed of sound is infinite, right?

But if it's essentially the same speed, then doesn't that just mean it's
a very close approximation? But we already agreed doppler distortion
(if it exists) is very small.

- Logan

[1] Non-zero, finite distance, I mean.
[2] Assuming the cone is changing speeds. Which, hopefully, it is.

[Chris Hornbeck]

On Thu, 12 Aug 2004 15:19:45 -0700, Bob Cain
> wrote:

>> Doppler has not escaped the attention of the technical community. There are
>> a number of JAES papers about it.
>
>Citations, please.

The papers by Klipsch, and by Allison and Villchur, toe their
respective party lines pretty closely re: audibility.

Colloms' _High Performance Loudspeakers_ gives a good
overview and very good references. Many are offended by
its tone, but that's the par on this course.

Good fortune, great topic, thanks,

Chris Hornbeck

[Noel Bachelor]

On or about Wed, 11 Aug 2004 13:10:23 GMT, Carey Carlan allegedly wrote:

> As a non-mathematical type I understood Doppler distortion to be caused
> when a high frequency was generated by a driver already in motion with a
> low frequency.
>
> The example was a woofer moving full excursion on a very low tone while
> generating a higher tone. Let's do an extreme case of a 10 Hz excursion
> and a 1000 Hz tone. Every 20th of a second (change in direction at 10 Hz)
> the pitch of the 1000 Hz tone would change as its vibrating medium (the
> woofer cone) changed from moving toward the listener to moving away.

Thanks. That helps me get a handle on this.

If they are real sounds, and were captured by a single microphone, then a
similar doppler shifting would be encoded by the microphone, so the
speaker would simply be decoding that, and effectively restoring the HF
tone to it's original timing. Of course the mic would typically have less
excursion than the speaker, but if frequency response was flat for both,
everything should be in the same balance.

If such a doppler encoded signal from a single mic is then reproduced on a
typical two way speaker system, then the hf component would have doppler
shifting that does not get decoded. But as others have mentioned,
multiway speakers would reduce that modulating effect, so perhaps are more
suited to reproducing material that has been mixed from widely different
sources so would not have the natural doppler encoding.

Sounds like a good argument for minimalist recording (one of many), and
don't touch that eq. at all, or you'll ruin everything.


Noel Bachelor noelbachelorAT(From:_domain)
Language Recordings Inc (Darwin Australia)

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
> >
> > ** If I read you correctly Bob:
> >
> >
> > 1. The air volume in close proximity to the cone of a woofer performing
low
> > frequency excursions moves with it as a whole - so they have
essentially
> > the same velocity at all times.
> >
> > 2. That means there is no effective cone / air velocity differential as
is
> > required to create the Doppler effect in air from the cone
simultaneously
> > vibrating at some high frequency.
> >
> > Is it as simple as that ?
>
> Yes, I think. Without pondering it deeply, it seems to be
> an accurate, yet different, way to state it and at least
> tentatively I think they are equivalent.
>


** Now I am interested in the **mechanism** that allows that volume air
moving in unison with a woofer cone with a high frequency pressure wave
travelling through it to *transfer* that high frequency wave to the still
air further away.





.............. Phil

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
> >
> > ** If I read you correctly Bob:
> >
> >
> > 1. The air volume in close proximity to the cone of a woofer performing
low
> > frequency excursions moves with it as a whole - so they have
essentially
> > the same velocity at all times.
> >
> > 2. That means there is no effective cone / air velocity differential as
is
> > required to create the Doppler effect in air from the cone
simultaneously
> > vibrating at some high frequency.
> >
> > Is it as simple as that ?
>
> Yes, I think. Without pondering it deeply, it seems to be
> an accurate, yet different, way to state it and at least
> tentatively I think they are equivalent.
>


** Now I am interested in the **mechanism** that allows that volume air
moving in unison with a woofer cone with a high frequency pressure wave
travelling through it to *transfer* that high frequency wave to the still
air further away.





.............. Phil

[Chris Hornbeck]

FWIW, I just slogged through the thread on rec.audio.tech
(much improved these days!) and found that it contained a
simple foolproof hardware test solution, by Paul Guy.

Since it didn't involve computers it was ignored. Gosh.

Chris Hornbeck

[Chris Hornbeck]

FWIW, I just slogged through the thread on rec.audio.tech
(much improved these days!) and found that it contained a
simple foolproof hardware test solution, by Paul Guy.

Since it didn't involve computers it was ignored. Gosh.

Chris Hornbeck

[Bob Cain]

Phil Allison wrote:

> "Bob Cain"
>
>>I've got an argument that so far has withstood some scrutiny
>>which shows that Doppler distortion in a myth.
>>
>
>
>
> ** This article has all the maths re the Doppler effect in woofers.
>
> http://www.geocities.com/kreskovs/Doppler1.html

Thanks, I'll give it a study. I've already found a wrong
working assumption, that the sound pressure created by a
driver is proportional to its acceleration rather than its
velocity and don't know yet how far that pervades the analysis.

That is the simplest refutation of Doppler, BTW. If the
pressure it creates is proportional to its velocity, which I
will believe until I see it proved otherwise, then since
velocities add linearly so will pressure and there can't be
modulation products.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:

> "Bob Cain"
>
>>I've got an argument that so far has withstood some scrutiny
>>which shows that Doppler distortion in a myth.
>>
>
>
>
> ** This article has all the maths re the Doppler effect in woofers.
>
> http://www.geocities.com/kreskovs/Doppler1.html

Thanks, I'll give it a study. I've already found a wrong
working assumption, that the sound pressure created by a
driver is proportional to its acceleration rather than its
velocity and don't know yet how far that pervades the analysis.

That is the simplest refutation of Doppler, BTW. If the
pressure it creates is proportional to its velocity, which I
will believe until I see it proved otherwise, then since
velocities add linearly so will pressure and there can't be
modulation products.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Jay Kadis wrote:

>
> In the case of lightning, isn't it the thermal expansion of the air that causes
> the sound of thunder?

Yes, but it isn't what makes an ion speaker speak. :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Jay Kadis wrote:

>
> In the case of lightning, isn't it the thermal expansion of the air that causes
> the sound of thunder?

Yes, but it isn't what makes an ion speaker speak. :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:

>>>Yes. That's how plasma speakers work. (I heard this
>>>straight from the mouth of Dr. Allen Hill.)
>
>
>>I don't think so. The plasma is an ionized state of air
>>which means it is charged and will move in response
>>to an applied electric field.
>
>
> You might choose so, but I'm inclined to believe the good Dr. He did a huge
> amount of both practical and theoretical research on ionic speakers -- he gave
> us a slide show -- before developing the Plasmatronics speaker.

Appeals to authority can be problematic. Check the theory
for yourself. No way to transfer heat into the air fast
enough to get any kind of bandwidth.

There are microphones, specifically the MicroFlown, that
measure the thermal gradients that exist in the wave but
their bandwidth isn't very high either despite the very low
thermal mass of the tiny detectors.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:

>>>Yes. That's how plasma speakers work. (I heard this
>>>straight from the mouth of Dr. Allen Hill.)
>
>
>>I don't think so. The plasma is an ionized state of air
>>which means it is charged and will move in response
>>to an applied electric field.
>
>
> You might choose so, but I'm inclined to believe the good Dr. He did a huge
> amount of both practical and theoretical research on ionic speakers -- he gave
> us a slide show -- before developing the Plasmatronics speaker.

Appeals to authority can be problematic. Check the theory
for yourself. No way to transfer heat into the air fast
enough to get any kind of bandwidth.

There are microphones, specifically the MicroFlown, that
measure the thermal gradients that exist in the wave but
their bandwidth isn't very high either despite the very low
thermal mass of the tiny detectors.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[George Perfect]

In this place, Bob Cain was recorded saying ...
>
> Thanks, I'll give it a study. I've already found a wrong
> working assumption, that the sound pressure created by a
> driver is proportional to its acceleration rather than its
> velocity and don't know yet how far that pervades the analysis.
>

See this also:

http://www.linkwitzlab.com/frontiers.htm#J

--
George
Newcastle, England

Problems worthy of attack
Prove their worth by hitting back - Piet Hein

[George Perfect]

In this place, Bob Cain was recorded saying ...
>
> Thanks, I'll give it a study. I've already found a wrong
> working assumption, that the sound pressure created by a
> driver is proportional to its acceleration rather than its
> velocity and don't know yet how far that pervades the analysis.
>

See this also:

http://www.linkwitzlab.com/frontiers.htm#J

--
George
Newcastle, England

Problems worthy of attack
Prove their worth by hitting back - Piet Hein

[Bob Cain]

Chris Hornbeck wrote:

> On Thu, 12 Aug 2004 15:19:45 -0700, Bob Cain
> > wrote:
>
>
>>>Doppler has not escaped the attention of the technical community. There are
>>>a number of JAES papers about it.
>>
>>Citations, please.
>
>
> The papers by Klipsch, and by Allison and Villchur, toe their
> respective party lines pretty closely re: audibility.
>
> Colloms' _High Performance Loudspeakers_ gives a good
> overview and very good references. Many are offended by
> its tone, but that's the par on this course.

Yeah, I'm hoping for citations that provide a complete
theory for the effect from which the result of any driving
point velocity or pressure can be predicted. There is no
good reason why this doesn't exist except possibly for one.

Everything is really subjective to this point without the
requisite separation of variables.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Chris Hornbeck wrote:

> On Thu, 12 Aug 2004 15:19:45 -0700, Bob Cain
> > wrote:
>
>
>>>Doppler has not escaped the attention of the technical community. There are
>>>a number of JAES papers about it.
>>
>>Citations, please.
>
>
> The papers by Klipsch, and by Allison and Villchur, toe their
> respective party lines pretty closely re: audibility.
>
> Colloms' _High Performance Loudspeakers_ gives a good
> overview and very good references. Many are offended by
> its tone, but that's the par on this course.

Yeah, I'm hoping for citations that provide a complete
theory for the effect from which the result of any driving
point velocity or pressure can be predicted. There is no
good reason why this doesn't exist except possibly for one.

Everything is really subjective to this point without the
requisite separation of variables.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:


>
> ** Now I am interested in the **mechanism** that allows that volume air
> moving in unison with a woofer cone with a high frequency pressure wave
> travelling through it to *transfer* that high frequency wave to the still
> air further away.

Look up "wave mechanics". Acoustics is just one of many
such systems that are formally equivalent.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:


>
> ** Now I am interested in the **mechanism** that allows that volume air
> moving in unison with a woofer cone with a high frequency pressure wave
> travelling through it to *transfer* that high frequency wave to the still
> air further away.

Look up "wave mechanics". Acoustics is just one of many
such systems that are formally equivalent.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
> >
> >>I've got an argument that so far has withstood some scrutiny
> >>which shows that Doppler distortion in a myth.
> >>
> > ** This article has all the maths re the Doppler effect in woofers.
> >
> > http://www.geocities.com/kreskovs/Doppler1.html
>
>
> Thanks, I'll give it a study. I've already found a wrong
> working assumption, that the sound pressure created by a
> driver is proportional to its acceleration rather than its
> velocity and don't know yet how far that pervades the analysis.
>

** That comment is quite accurate - cone acceleration is the parameter
that matches radiated SPL from a moving cone.
Consider that the force acting on a voice coil is proportional to the
applied current and the moving mass is fixed. From F = mA we have the result
that cone acceleration is proportional to applied current at any instant.


> That is the simplest refutation of Doppler, BTW. If the
> pressure it creates is proportional to its velocity, which I
> will believe until I see it proved otherwise, then since
> velocities add linearly so will pressure and there can't be
> modulation products.


** Dunno what you are on about - Doppler is a linear phenomenon, not some
kind of distortion product. It is simply the result of a moving source
creating longer or shorter wavelengths in the air than it would if
stationery.

Shame that dumb spectrum analysers cannot tell the difference between
minor amounts of AM and very narrow FM with a high index figure - that
fact has cast doubt over practically all the test results that are claimed
to show Doppler shift in the sound coming from woofers.




............... Phil

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
> >
> >>I've got an argument that so far has withstood some scrutiny
> >>which shows that Doppler distortion in a myth.
> >>
> > ** This article has all the maths re the Doppler effect in woofers.
> >
> > http://www.geocities.com/kreskovs/Doppler1.html
>
>
> Thanks, I'll give it a study. I've already found a wrong
> working assumption, that the sound pressure created by a
> driver is proportional to its acceleration rather than its
> velocity and don't know yet how far that pervades the analysis.
>

** That comment is quite accurate - cone acceleration is the parameter
that matches radiated SPL from a moving cone.
Consider that the force acting on a voice coil is proportional to the
applied current and the moving mass is fixed. From F = mA we have the result
that cone acceleration is proportional to applied current at any instant.


> That is the simplest refutation of Doppler, BTW. If the
> pressure it creates is proportional to its velocity, which I
> will believe until I see it proved otherwise, then since
> velocities add linearly so will pressure and there can't be
> modulation products.


** Dunno what you are on about - Doppler is a linear phenomenon, not some
kind of distortion product. It is simply the result of a moving source
creating longer or shorter wavelengths in the air than it would if
stationery.

Shame that dumb spectrum analysers cannot tell the difference between
minor amounts of AM and very narrow FM with a high index figure - that
fact has cast doubt over practically all the test results that are claimed
to show Doppler shift in the sound coming from woofers.




............... Phil

[Bob Cain]

Phil Allison wrote:


>>Thanks, I'll give it a study. I've already found a wrong
>>working assumption, that the sound pressure created by a
>>driver is proportional to its acceleration rather than its
>>velocity and don't know yet how far that pervades the analysis.
>>
>
>
> ** That comment is quite accurate - cone acceleration is the parameter
> that matches radiated SPL from a moving cone.
> Consider that the force acting on a voice coil is proportional to the
> applied current and the moving mass is fixed. From F = mA we have the result
> that cone acceleration is proportional to applied current at any instant.

Ok. The false assumption is that the pressure wave created
by a piston is proportional to its acceleration. It isn't;
it's proprotional to the piston velocity.

As I said, I don't know yet how much, if any, this
misconception invalidates the two tone analysis that I'm
ready to dig into after a night's sleep.

> ** Dunno what you are on about - Doppler is a linear phenomenon, not some
> kind of distortion product. It is simply the result of a moving source
> creating longer or shorter wavelengths in the air than it would if
> stationery.

Didn't I explain what a linear system is in a prior post?
Nothing that produces "frequencies" that aren't in what's
driving it is linear. It's one of several equivalent
definitions of linear.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:


>>Thanks, I'll give it a study. I've already found a wrong
>>working assumption, that the sound pressure created by a
>>driver is proportional to its acceleration rather than its
>>velocity and don't know yet how far that pervades the analysis.
>>
>
>
> ** That comment is quite accurate - cone acceleration is the parameter
> that matches radiated SPL from a moving cone.
> Consider that the force acting on a voice coil is proportional to the
> applied current and the moving mass is fixed. From F = mA we have the result
> that cone acceleration is proportional to applied current at any instant.

Ok. The false assumption is that the pressure wave created
by a piston is proportional to its acceleration. It isn't;
it's proprotional to the piston velocity.

As I said, I don't know yet how much, if any, this
misconception invalidates the two tone analysis that I'm
ready to dig into after a night's sleep.

> ** Dunno what you are on about - Doppler is a linear phenomenon, not some
> kind of distortion product. It is simply the result of a moving source
> creating longer or shorter wavelengths in the air than it would if
> stationery.

Didn't I explain what a linear system is in a prior post?
Nothing that produces "frequencies" that aren't in what's
driving it is linear. It's one of several equivalent
definitions of linear.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Arny Krueger]

"Noel Bachelor" > wrote in message

> On or about Wed, 11 Aug 2004 13:10:23 GMT, Carey Carlan allegedly
> wrote:
>
>> As a non-mathematical type I understood Doppler distortion to be
>> caused when a high frequency was generated by a driver already in
>> motion with a low frequency.
>>
>> The example was a woofer moving full excursion on a very low tone
>> while generating a higher tone. Let's do an extreme case of a 10
>> Hz excursion and a 1000 Hz tone. Every 20th of a second (change in
>> direction at 10 Hz) the pitch of the 1000 Hz tone would change as
>> its vibrating medium (the woofer cone) changed from moving toward
>> the listener to moving away.

> Thanks. That helps me get a handle on this.

> If they are real sounds, and were captured by a single microphone,
> then a similar doppler shifting would be encoded by the microphone,
> so the speaker would simply be decoding that, and effectively
> restoring the HF tone to it's original timing.

The cause of Doppler distortion is large amounts of diaphragm displacement.
Because the diaphragm in microphones is so small, they cause very little
Doppler distortion. Therefore, it is highly unlikely that a microphone would
be able to compensate for Doppler distortion in a loudspeaker.

[Arny Krueger]

"Noel Bachelor" > wrote in message

> On or about Wed, 11 Aug 2004 13:10:23 GMT, Carey Carlan allegedly
> wrote:
>
>> As a non-mathematical type I understood Doppler distortion to be
>> caused when a high frequency was generated by a driver already in
>> motion with a low frequency.
>>
>> The example was a woofer moving full excursion on a very low tone
>> while generating a higher tone. Let's do an extreme case of a 10
>> Hz excursion and a 1000 Hz tone. Every 20th of a second (change in
>> direction at 10 Hz) the pitch of the 1000 Hz tone would change as
>> its vibrating medium (the woofer cone) changed from moving toward
>> the listener to moving away.

> Thanks. That helps me get a handle on this.

> If they are real sounds, and were captured by a single microphone,
> then a similar doppler shifting would be encoded by the microphone,
> so the speaker would simply be decoding that, and effectively
> restoring the HF tone to it's original timing.

The cause of Doppler distortion is large amounts of diaphragm displacement.
Because the diaphragm in microphones is so small, they cause very little
Doppler distortion. Therefore, it is highly unlikely that a microphone would
be able to compensate for Doppler distortion in a loudspeaker.

[Arny Krueger]

"William Sommerwerck" > wrote in message

>> Also the modulated-arc "ion" speakers and the modulated flame
>> (I **** thee not) speakers used in Vietnam for propaganda flights.
>
> Flame speakers actually date to the late 19th century. They worked,
> but were noisy.
>
> There have been several ionic speakers, most notably the DuKane
> Ionovac tweeter, and the Hill Plasmatronic speaker, which was ionic
> from 700Hz up.

Here's some modern examples:

http://www.plasmatweeter.de/

http://www.audiophilia.com/hardware/acapella.htm

[Arny Krueger]

"William Sommerwerck" > wrote in message

>> Also the modulated-arc "ion" speakers and the modulated flame
>> (I **** thee not) speakers used in Vietnam for propaganda flights.
>
> Flame speakers actually date to the late 19th century. They worked,
> but were noisy.
>
> There have been several ionic speakers, most notably the DuKane
> Ionovac tweeter, and the Hill Plasmatronic speaker, which was ionic
> from 700Hz up.

Here's some modern examples:

http://www.plasmatweeter.de/

http://www.audiophilia.com/hardware/acapella.htm

[Arny Krueger]

"Chris Hornbeck" > wrote in message


> FWIW, I just slogged through the thread on rec.audio.tech
> (much improved these days!) and found that it contained a
> simple foolproof hardware test solution, by Paul Guy.

> Since it didn't involve computers it was ignored. Gosh.

Yes, it's a good post. However, I have experimented with many of the
approaches he suggested in the past, relating to jitter.

Hate to break your bubble - but my experiments were all done with
Audition/CE and Spectra. ;-)

Here's his post with my comments:

>If you are trying to discriminate FM from AM, you can look at the envelope.
AM (IM) distortion should have a typical modulation pattern.

In fact this only works effectively if you are trying to distinguish pure FM
from pure AM. The real world of speaker distortion rarely involves pure
anything!

>You might need to use some electronics to AM detect the envelope. ie.,
bandpass filter for 4000 Hz,

The Audition/CE FFT filter does this very well!

>envelope detector,

Square the signal with mix/paste modulate, and then low pass filter it with
the FFT filter or one of the scientific filters

>then watch the AC component at the output, just like a typical AM receiver.

Been there done that, see former comments about mixed AM & FM in the real
world.

> For the FM component, clip the signal,

over-amplify the signal in 16 bit mode

> put the resultant in a 4 khz bandpass,

the Audition/CE FFT filter does this very well

>or just measure the sidebands around 4 KHz.

Been there done that, see former comments about mixed AM & FM in the real
world.

>The only difference between AM (IM) and FM (phase) modulation is the phase
of the two sidebands. AM they are both in phase (they add to the overall
amplitude). In FM they are out of phase, thus they have no
effect on the amplitude. The individual amplitudes are the same
between AM and FM, assuming the FM is of small deviation (yours is not
all that small).

This is all quite basic and true. It turns out that with both jitter and
Doppler, the amount of FM is small.

This suggests another means of detection. Mix/Paste the signal under test
with a synthetic signal that has equal-sized sidebands at the same
frequencies, but in-phase with the carrier. If the signal is AM the
sidebands add, but if the signal is FM, the sidebands have different
amplitudes.

[Arny Krueger]

"Chris Hornbeck" > wrote in message


> FWIW, I just slogged through the thread on rec.audio.tech
> (much improved these days!) and found that it contained a
> simple foolproof hardware test solution, by Paul Guy.

> Since it didn't involve computers it was ignored. Gosh.

Yes, it's a good post. However, I have experimented with many of the
approaches he suggested in the past, relating to jitter.

Hate to break your bubble - but my experiments were all done with
Audition/CE and Spectra. ;-)

Here's his post with my comments:

>If you are trying to discriminate FM from AM, you can look at the envelope.
AM (IM) distortion should have a typical modulation pattern.

In fact this only works effectively if you are trying to distinguish pure FM
from pure AM. The real world of speaker distortion rarely involves pure
anything!

>You might need to use some electronics to AM detect the envelope. ie.,
bandpass filter for 4000 Hz,

The Audition/CE FFT filter does this very well!

>envelope detector,

Square the signal with mix/paste modulate, and then low pass filter it with
the FFT filter or one of the scientific filters

>then watch the AC component at the output, just like a typical AM receiver.

Been there done that, see former comments about mixed AM & FM in the real
world.

> For the FM component, clip the signal,

over-amplify the signal in 16 bit mode

> put the resultant in a 4 khz bandpass,

the Audition/CE FFT filter does this very well

>or just measure the sidebands around 4 KHz.

Been there done that, see former comments about mixed AM & FM in the real
world.

>The only difference between AM (IM) and FM (phase) modulation is the phase
of the two sidebands. AM they are both in phase (they add to the overall
amplitude). In FM they are out of phase, thus they have no
effect on the amplitude. The individual amplitudes are the same
between AM and FM, assuming the FM is of small deviation (yours is not
all that small).

This is all quite basic and true. It turns out that with both jitter and
Doppler, the amount of FM is small.

This suggests another means of detection. Mix/Paste the signal under test
with a synthetic signal that has equal-sized sidebands at the same
frequencies, but in-phase with the carrier. If the signal is AM the
sidebands add, but if the signal is FM, the sidebands have different
amplitudes.

[Arny Krueger]

"Bob Cain" > wrote in message

> Arny Krueger wrote:
>
>
>> Doppler has not escaped the attention of the technical community.
>> There are a number of JAES papers about it.

> Citations, please.


The Audibility of Doppler Distortion in Loudspeakers 1035944 bytes (CD
aes10)
Author(s): Allison, Roy; Villchur, Edgar
Publication: Preprint 1844; Convention 70; October 1981
Abstract: Although Doppler distortion in loudspeakers has been often viewed
with alarm since Beers and Belar described it in 1943, the question of its
significance in music reproduction has not yet been answered. In this study
the audibility of Doppler distortion in simple direct radiators is
investigated theoretically (by analogy to tape-machine flutter and by
analysis of blind listening-room acoustic effects), and experimentally (by
double-blind listening tests). The analysis predicts Doppler inaudibility
for any practical cone velocity, and the experimental results provide
confirming evidence.

The Audibility of Doppler Distortion in Loudspeakers 1059616 bytes (CD
aes10)
Author(s): Allison, Roy; Villchur, Edgar
Publication: Preprint 1769; Convention 69; May 1981
Abstract: Although Doppler distortion in loudspeakers has been often viewed
with alarm since Beers and Belar described it in 1943, the question of its
significance in music reproduction has not yet been answered. In this study
the audibility of Doppler distortion in simple direct radiators is
investigated theoretically (by analogy to tape-machine flutter and by
analysis of listening room acoustic effects), and experimentally (by
double-blind listening tests). The analysis predicts Doppler inaudibility
for any practical cone velocity, and the experimental results provide
confirming evidence.

On the Magnitude and Audibility of FM Distortion in Loudspeakers 732451
bytes (CD aes4)
Author(s): Allison, Roy; Villchur, Edgar
Publication: Volume 30 Number 10 pp. 694·700; October 1982
Abstract: Beers and Belar, in their 1943 paper on Doppler effect in
loudspeakers, recognized and pointed out limitations in the scope of their
analysis. They also suggested simple methods for keeping FM distortion
products below the level of audibility, such as dividing the spectrum among
at least two drivers. Recent work is described which extends Beers and
Belar's analysis along lines they suggested, and which, by means of
double-blind listening tests, provides confirming evidence that Doppler
distribution in practical multidriver systems is indeed inaudible.

Simulation and Investigation of Doppler Distortion 402761 bytes (CD aes9)
Author(s): Fryer, P. A.
Publication: Preprint 1197; Convention 56; March 1977
Abstract: Doppler distortion audibility has been assessed using two delay
lines. The clock frequency of one is varied in accordance with the Doppler
formula and the other is the idle of the first. Their subtracted outputs,
therefore, give a measure of the simulated Doppler distortion present.
Progressive reduction of the simulation on A-B tests gives lowest detectable
levels.

Implementing Doppler Shifts for Virtual Auditory Environments 1062709 bytes
(CD aes14)
Author(s): Strauss, Holger
Publication: Preprint 4687; Convention 104; May 1998
Abstract: A listening test has shown that the plausibility of virtual
auditory environments can be increased significantly when Doppler shifts are
adequately emulated. A simple sound-field model capable of calculating the
necessary auralization parameters for moving sound sources and listeners in
real-time applications is presented. Signal processing algorithms for
auralizing Doppler shifts are discussed.

Loudspeaker Distortion with Low-Frequency Signals 1222990 bytes (CD aes3)
Author(s): Harwood, H.D.
Publication: Volume 20 Number 9 pp. 718·728; November 1972
Abstract: Three differing forms of distortion, which are associated with
low-frequency signals in loudspeakers, are investigated. It is shown that
distortion due to the Doppler effect can be compared with that due to wow
and flutter in recording machines, and subjective data obtained for this
purpose can be applied to loudspeakers. Generalized design limits for
loudspeakers are calculated. In loudspeakers designed to reproduce low
frequencies, the voice coil is made longer than the magnetic field. At low
frequencies, when the amplitude of vibration of the cone exceeds the
difference in length, it is shown that instead of the peaks of the waveform
being clipped, expansion of the input-output curve takes place. This effect,
with its associated distortion, can be compensated by employing an
appropriate nonlinear suspension, and thus a much greater useful output can
be obtained than by using a linear suspension. Finally, a vented cabinet is
often used to reduce the magnitude of the undesirable effects previously
mentioned as well as to extend the bass response. However, a vented cabinet
is a resonant system and high sound pressures and particle velocities are
produced in the vent. These are liable to give rise to distortion from the
inherent nonlinearity in the air and from turbulence at the orifice and in
the pipe. Existing data ae used to estimate the sound levels which may be
generated in a typical listening room before distortions from any of these
causes are audible. It is also shown that this form of distortion is not a
troublesome factor in the design of studio monitoring loudspeakers.

Magnitude Estimation of Sound Source Speed 115837 bytes (CD aes15)
Author(s): Ericson, Mark A.
Publication: Preprint 5209; Convention 109; September 2000
Abstract: Linear motion of a harmonic sound source was simulated for various
trajectory paths. The acoustic signal was processed with frequency and
intensity changes because of Doppler shifts in frequency, overall intensity
changes, and atmospheric absorption. While listening to these sounds over
headphones, four participants were asked to make magnitude estimations of
the sound source speed under various combinations of motion effects. The
frequency and intensity changes were found to contribute to the ability of
the listeners to judge sound source speed. Inclusion of these motion
attributes produced a veridical simulation of sound source motion.

On the Doppler Distortion in Loudspeakers 867677 bytes (CD aes3)
Author(s): Braun, S.
Publication: Volume 21 Number 3 pp. 185·187; April 1973
Abstract: A short review of Doppler distortion is given. An experimental
setup isolating this effect from nonlinearity-induced distortion is
described and its feasibility tested.

Prediction of Speaker Performance at High Amplitudes 591237 bytes (CD
aes18)
Author(s): Klippel, Wolfgang
Publication: Preprint 5418; Convention 111; December 2001
Abstract: A new method is presented for the numerical simulation of the
large signal performance of drivers and loudspeaker systems. The basis is an
extended loudspeaker model considering the dominant nonlinear and thermal
effects. The use of a two-tone excitation allows the response of
fundamental, DC-component, harmonics, and intermodulation components to be
measured as a function of frequency and amplitude. After measurement of the
linear and nonlinear parameters, the electrical, mechanical, and acoustical
state variables may be calculated by numerical integration. The relationship
between large signal parameters and non-linear transfer behavior is
discussed by modeling two drivers. The good agreement between simulated and
measured responses shows the basic modeling, parameter identification, and
numerical predictions are valid even at large amplitudes. The method
presented reduces time-consuming measurements and provided essential
information for quality assessment and diagnosis. The extended loudspeaker
model also allows prediction of design changes on the large signal
performance by changing the model parameters to reflect the driver design
changes. The incorporation of nonlinear parameters into the loudspeaker
model allows for optimization in both the small and large signal domains by
model prediction.

Multitone Testing of Sound System Components·Some Results and Conclusions,
Part 1: History and Theory 2073763 bytes (CD aes18)
Author(s): CZERWINSKI, EUGENE; VOISHVILLO, ALEXANDER; ALEXANDROV, SERGEI;
TEREKHOV, ALEXANDER
Publication: Volume 49 Number 11 pp. 1011-1048; November 2001
Abstract: An historical retrospective analysis of the measurement of
nonlinearities in audio is carried out. A quantitative analysis of the
responses of various nonlinear systems (theoretical and experimental) to a
multitone signal is made, and multitone testing is compared to conventional
harmonic and intermodulation measurements. The multitone test provides more
accurate information about the behavior of nonlinear systems when compared
to standard harmonic, two-tone intermodulation, and total harmonic
distortion measurements. Modeling of the nonlinear reaction of various sound
system components to a multitone signal is described.

Doppler-Type Organ Tone Cabinet 295593 bytes (CD aes2)
Author(s): Machanian, William V.
Publication: Volume 10 Number 3 pp. 216·218; July 1962
Abstract: The problems confronting the designer of organ tone cabinets are
analyzed. Two different requirements must be satisfied for a Doppler-type
tone cabinet design. One requirement is the faithful reproduction of the
generated musical tones with a minimum of distortion. Th'second requirement
relates to Doppler modulation of the musical signal to provide what is
called a ·vibrato· effect.

Subwoofer Performance for Accurate Reproduction of Music 1682416 bytes (CD
aes11)
Author(s): Fielder, Louis D.; Benjamin, Eric M.
Publication: Preprint 2537; Convention 83; October 1987
Abstract: The spectra and maximum output levels for accurately reproducing
low frequency musical signals are determined from published research and new
measurements. Analysis of commercial recording shows substantial musical
information in the octave from 32 to 16 Hz and some down to 12 Hz.
Psychoacoustic data are used to establish to what degree errors (such as
THD, FM distortion, modulation noise, and bandwidth limits) are perceptible.
Criteria are set for proper subwoofer performance at peak levels of 110 dB
SPL.

Subwoofer Performance for Accurate Reproduction of Music 1546477 bytes (CD
aes4)
Author(s): Fielder, Louis D.; Benjamin, Eric M.
Publication: Volume 36 Number 6 pp. 443·456; June 1988
Abstract: The spectra and the maximum output levels for accurately
reproducing low-frequency musical signals are determined from published
research and new measurements. Analysis of commercial recordings shows
substantial musical information in the octave from 32 to 16 Hz and some down
to 12 Hz. Psychoacoustic data are used to establish to what degree errors
(such as total harmonic distortion, FM distortion, modulation noise, and
bandwidth limits) are perceptible. Criteria are set for proper subwoofer
performance at peak sound pressure levels of 110 dB.

Doppler Distortion in Loudspeakers 763066 bytes (CD aes8)
Author(s): Moir, James
Publication: Preprint 925; Convention 46; September 1973
Abstract: In 1942 two R.C.A. engineers, G.L. Beers ahd H. Belar, drew
attention to the presence of a form of distortion in loudspeaker
reproduction not previously identified. It is the result of modulation of
the frequency of one signal by the frequency of a second signal
simultaneously applied. Because of the difficulties in obtaining reliable
quantitative data on the extent of this distortion, its existence has been
challenged by many writers and though its presence has been conclusively
proved by Klipsch, More, Braun and others, its importance may still be in
doubt. It is the purpose of the present contribution to describe some simple
techniques for the segregation and measurement of this form of distortion
and to provide data on its magnitude in some typical commercial speaker
systems.

Moving Boundary Condition and Nonlinear Propagation as the Sources of
Nonlinear Distortion in Loudspeakers 596452 bytes (CD aes12)
Author(s): Zóltogórski, Bronislaw
Publication: Preprint 3510; Convention 94; March 1993
Abstract: Two natural phenomena connected with the excitation of acoustic
waves by moving the loudspeaker diaphragm are considered: 1) effect of a
moving boundary condition traditionally named the Doppler effect; and 2)
effect of nonlinear propagation of acoustic waves. In this paper, it is
shown that distortions caused by nonlinear propagation have negligible
magnitude; and that an improved expression for the coefficient of
Doppler-type distortions is derived. A concept of an anti-Doppler filter is
presented.

Moving Boundary Conditions and Nonlinear Propagation as Sources of
Nonlinear Distortions in Loudspeakers 614943 bytes (CD aes5)
Author(s): Zóltogórski, Bronislaw
Publication: Volume 41 Number 9 pp. 691·700; September 1993
Abstract: Two phenomena connected with the generation of acoustic waves by a
loudspeaker diaphragm are considered: 1) the effect of moving boundary
conditions, traditionally called the Doppler effect, and 2) the effect of
nonlinear acoustic wave propagation. It is shown that distortions caused by
moving boundary conditions are dominant in a low-frequency range. An
improved expression is derived for the coefficient of Doppler-type
distortions, and an idea for an anti-Dopper filter is presented.

The Mirror Filter·A New Basis for Linear Equalization and Nonlinear
Distortion Reduction of Woofer Systems 1459125 bytes (CD aes12)
Author(s): Klippel, Wolfgang
Publication: Preprint 3221; Convention 92; March 1992
Abstract: A new filter structure derived from the nonlinear differential
equation and switched into the electrical path enables the reduction of
nonlinear distortions of loudspeakers caused by displacement of varying
parameters (force factor, stiffness, and inductance) and Doppler effect.
Simultaneously, this filter is used for optimizing the linear frequency
response (resonance frequency and Q-factor) and for realizing an effective
protection against destruction. Unlike feedback systems, no permanent sensor
is required. To adjust the filter parameters to the actual loudspeaker
automatically, an iterative method is presented which is based on the
electrical or acoustical measurement of the overall transfer response. Both
the filter and the auxiliary systems for protection and adjustment are
implemented in a DSP 56001 and result in a self-learning distortion
reduction system. This system was tested on different loudspeakers. Results
are contrasted to the listening impression and possible consequences to
loudspeaker design are discussed.

The Mirror Filter·A New Basis for Reducing Nonlinear Distortion and
Equalizing Response in Woofer Systems 1289233 bytes (CD aes5)
Author(s): Klippel, Wolfgang
Publication: Volume 40 Number 9 pp. 675·691; September 1992
Abstract: A new filter structure, derived from the applicable nonlinear
differential equation and inserted in the signal path, reduced loudspeaker
nonlinear distortion caused by displacement-sensitive parameters (force
factor, stiffness, and inductance) and by the Doppler effect. This filter
can also be used for optimizing the linear frequency response (resonance
frequency and Q factor) and for protecting against mechanical damage. There
is no need for a permanent sensor, a requirement in feedback systems. To
adjust the filter parameters automatically to a particular loudspeaker, an
iterative method is presented, based on the electrical or acoustical
measurement of the overall transfer response. Both the filter and the
auxiliary systems for protection and adjustment are implemented in a DSP
56001 and result in a self-learning distortion-reduction system. The system
was tested on different loudspeakers, and the measurement results are
compared with listening impressions. The possible consequences in
loudspeaker design are discussed.

Frequency-Modulation Distortion in Loudspeakers (Reprint) 693548 bytes (CD
aes4)
Author(s): Beers, G.L.; Belar, H.
Publication: Volume 29 Number 5 pp. 320·326; May 1981
Abstract: As the frequency-response range of a sound-reproducing system is
extended, the necessity for minimizing all forms of distortion is
correspondingly increased. The part which the loudspeaker can contribute to
the overall distortion of a reproducing system has been frequently
considered. A type of loudspeaker distortion which has not received general
consideration is described. This distortion is a result of the
Doppler-effect and produces frequency modulation in loudspeakers reproducing
complex tones. Equations for this type of distortion are given. Measurements
which confirm the calculated distortion in several loudspeakers are shown.
An appendix giving the derivation of the equations is included.
Contactless Flaw Detection Based on the Doppler Effect 242797 bytes (CD
aes11)
Author(s): Cherek, B.; Armannson, J. H.; Delsanto, P. P.
Publication: Preprint 2785; Convention 86; March 1989
Abstract: A nondestructive flaw detection technique, based on a contactless
device is presented. To demonstrate its applicability, measurements have
been performed on several A1 plates before and after flawing them with one
or more scratches. A spectrum analysis shows a significant change in the
height of the odd harmonics, which increases with the number and size of the
scratches.

Automatic Vibration Analysis by Laser Interferometry 314875 bytes (CD
aes11)
Author(s): Wright, J. R.
Publication: Preprint 2889; Convention 88; March 1990
Abstract: A new measurement system for non-contact vibration analysis has
been developed, using the scanning laser interferometry method to measure
local velocities of a vibrating surface. The system can run as a fully
automated (unmanned) test, and has applications in structural or modal
analysis in fields as diverse as the motor industry, transducer design, or
building vibration measurement.

A Non-Linear Model of a Small Transducer 783682 bytes (CD aes17)
Author(s): Backman, Juha
Publication: Paper MAL-10; Conference: AES UK Conference: Microphones &
Loudspeakers, The Ins & Outs of Audio (MAL); March 1998
Abstract: The paper presents a model for an inherent distortion caused by
flow resistance modulation in small transducers. The distortion mechanisms
analysed here include the modulation of the transducer's moving mass, its
compliance, and the viscous damping. A numerical model is presented for
different forms of non-linearity, and examples indicating the significance
of the non-linear effects are computed.

Objective Characterization of Audio Sound Fields in Automotive Spaces
3625082 bytes (CD aes16)
Author(s): Kleiner, Mendel; Lindgren, Claes
Publication: Paper 15-007; Conference: The AES 15th International
Conference: Audio, Acoustics & Small Spaces; October 1998
Abstract: The properties of sound fields in cars are of great interest. A
considerable part of the daily noise exposure of many people is obtained
while driving. The car compartment today is also the primary music listening
environment for many people, and many people spend considerable amounts of
money on car audio equipment. Audio for the car environment requires
different engineering tradeoffs than for the home environment. The cognitive
aspect for car audio equipment may be larger than for domestic equipment.
The car is for many the most important status symbol. Also, the presence of
noise while listening to voice and music results in different system
criteria. Consequently, understanding the electroacoustics and room
acoustics of the car audio environment is important. Audio system design
criteria have to be set by and for measurements. Most conventional acoustic
measures are of interest in the car acoustics measurement but emphasis is
shifted to the sound pressure at the listener's position. The audio measures
have to be modified because of the special listening circumstance due to the
small size of the compartment. The field offers many opportunities for
further research in order to find objective measures that describe the
listening experience well.

Distortion from Boundary Layers 632495 bytes (CD aes14)
Author(s): Backman, Juha
Publication: Preprint 4619; Convention 103; September 1997
Abstract: The paper presents a model for an inherent distortion caused by
flow resistance modulation in small transducers. This type of distortion is
most significant near the resonance frequency of the transducer, and can be
an important factor in limiting the transducer performance. A numerical
model is presented for different forms of nonlinearity, and examples of the
nonlinear effects are computed.

A Reliable Method of Loudspeaker Rub and Buzz Testing Using Automated FFT
Response and Distortion Techniques 4029773 bytes (CD aes12)
Author(s): Groeper, Gregory G.; Blanchard, Mark A.; Brummett, Terry; Bailey,
Jeff
Publication: Preprint 3161; Convention 91; October 1991
Abstract: By utilizing modern DSP technology and FFT spectral analysis, and
by applying some aspects of human hearing and psychoacoustics, a reliable
method of rub and buzz distortion testing for loudspeakers can be devised
for a wide variety of engineering and production applications. Additionally,
test times can be radically reduced, thus contributing favorably to outside
noise rejection and a higher degree of repeatability. Examples of test
results include comparisons of good and bad units and feature standard cone
type loudspeakers and compression drivers showing varying degrees of
conformity. In the final analysis, loudspeakers are tested for polarity,
frequency response and different types of distortion.

Modulation Distortion in Loudspeakers 2374573 bytes (CD aes3)
Author(s): Klipsch, Paul W.
Publication: Volume 17 Number 2 pp. 194, 196, 198, 200, 202, 204, 206; April
1969
Abstract: When comparing a loudspeaker with direct radiator bass system to
one with horn loaded bass, the subjective judgment is that the one with the
horn loaded bass is ·cleaner.· The difference in listening quality appears
to be due to modulation distortion. The mathematical analysis of modulation
distortion is reviewed and spectrum analyzer measurements are described
which have been correlated with listening tests. The spectrum analyses
corroborate the mathematical analysis and the listening tests offer a
subjective evaluation. It is concluded that frequency modulation in
loudspeakers accounts in large measure for the masking of ·inner voices.·
Reduction of diaphragm excursions at low frequencies reduces FM distortion.
Horn loading, properly applied, offers greatest reduction, while
simultaneously improving bass power output capability.

Why and How to Measure Distortion in Electroacoustic Transducers 1588948
bytes (CD aes16)
Author(s): Temme, Steve
Publication: Paper 11-028; Conference: The AES 11th International
Conference: AES Test & Measurement Conference; May 1992
Abstract: In the never-ending quest for better sound transmission,
reinforcement, and reproduction, the electronics has been extensively
analyzed for distortion. Distortion in electroacoustic transducers, while
typically several orders of magnitude greater, has often been neglected or
not even specified because it has been difficult to measure and interpret.
With a basic understanding of transducer limitations, some knowledge of
human hearing, and the application of different distortion test methods,
electroacoustic transducer distortion becomes easier to measure and assess.


T/60·How Do I Measure Thee, Let Me Count the Ways 4227391 bytes (CD aes11)
Author(s): D'Antonio, Peter; Eger, Don
Publication: Preprint 2368; Convention 81; November 1986
Abstract: A comparison of T60 values obtained in a certified NVLAP
reverberation chamber using conventional 1/3-octave decaying sound pressure
level (SPL method) measurements and time-delay spectrometry (TDS) is
presented. The TDS measurements were obtained from the least-squares slope
of a backward Schroeder integration of the total energy density versus time
for 16 fixed-bandwidth (1333 Hz) energy-time curves (ETC method) at
1/3-octave center frequencies and from a Peutz regression analysis of
1/3-octave averaged time-energy-frequency 3-D curves (TEF method). The SPL
method utilized a rotating microphone and a rotating vane diffuser. The ETC
and TEF methods were conducted with all combinations of rotating or
stationary microphone and vane diffuser, to evaluate their effect. The best
agreement between the SPL and ETC method was obtained using a spatial
averaging of stationary microphone measurements with the rotating vanes
stationary. The rotating vanes introduce the amplitude and frequency
modulation interference which caused discrepancies at frequencies of 1000 Hz
and higher, resulting in excessively large apparent T60s. On the other hand,
the best agreement between the SPL and TEF method was achieved using a
spatial average of stationary microphone measurements with the vanes
rotating. Stopping the vanes in the TEF method caused large discrepancies at
low frequencies of 500 Hz and below. This results from a decrease in the
number of excited modes which occurs when the Doppler effect of the rotating
vanes is removed. No advantage was realized infusing the moving microphone
technique in the TDS procedures. Since efficient broad-bandwidth wide-angle
fixed sound diffusers are now available, i the form of reflection phase
gratings, it should be possible to create a uniformly diffuse sound field
without rotating vanes, thus creating an environments where all T60
techniques could be performed accurately. A significant difference between
our integrated total energy density curves (TETC) and those of other
researchers using the integrated impulse response squared (IIR), is the
absence of spatially dependent fluctuations, even at 125 Hz, in our results.
A comparison between the IIR and IETC methods at 125 Hz, 250 Hz, and 500 Hz,
for the condition where the microphone and vanes were stationary, revealed
that the IIR curves were slightly more irregular but the overall backward
integration envelopes were similar. T60s obtained from the IIR for these
frequencies were approximately 4% lower than the IETC. Based on this
comparison and the smooth linearity of the decay curves, we conclude that
the sound field in the chamber was adequately diffuse.

The Modeling of the Nonlinear Response of an Electrodynamic Loudspeaker by
a Volterra Series Expansion 714668 bytes (CD aes11)
Author(s): Kaizer, A. J. M.
Publication: Preprint 2355; Convention 80; March 1986
Abstract: An electrodynamic loudspeaker is often assumed to be a linear
system. However, actual loudspeakers show small nonlinearities that give
rise to distortion components in its response. An overview of possible
nonlinearities in a practical electrodynamic loudspeaker is given in this
paper. The paper also presents a model of the nonlinear loudspeaker
behavior, which can be used to predict the low-frequency distortion of a
loudspeaker.

Modeling of the Nonlinear Response of an Electrodynamic Loudspeaker by a
Volterra Series Expansion 944788 bytes (CD aes4)
Author(s): Kaizer, A. J. M.
Publication: Volume 35 Number 6 pp. 421·433; June 1987
Abstract: The modeling of low-frequency nonlinear distortion in the response
of an electrodynamic loudspeaker by a Volterra series expansion is
described, an extension of ordinary linear network theory. A nonlinear
inversion circuit based on the Volterra series expansion, which is capable
of reducing the nonlinearities in the response, is described theoretically.
The harmonic and intermodulation distortion products of an actual
loudspeaker have been calculated using this tool. The distortion curves
predicted by the model and the measured distortion curves show a reasonable
agreement.

Amplitude and Frequency Modulation Distortions of a Loudspeaker 703036
bytes (CD aes4)
Author(s): Suzuki, Hideo; Shibata, Shigenori
Publication: Volume 32 Number 4 pp. 246-253; April 1984
Abstract: The measurement techniques and the causes of amplitude and
frequency modulation distortions are discussed using a two-way coaxial-type
loudspeaker system. The distortion due to amplitude modulation is caused by
the dependence of the radiation efficiency of the high-frequency driver on
the displacement of the diaphragm of the low-frequency driver. The
distortion due to frequency modulation seems to be produced when the
high-frequency sound has a nonzero particle velocity in the axis direction
at the surface of the low-frequency driver diaphragm. The symmetry of the
sidebands of the summed modulation distortion (intermodulation distortion)
indicates that the amplitude and frequency modulation distortions are 90°
out of phase with each other.

Amplitude and Frequency Modulation Distortion of a Loudspeaker 695994 bytes
(CD aes10)
Author(s): Suzuki, Hideo; Shibata, Shigenori
Publication: Preprint 1998; Convention 74; October 1983
Abstract: The measurement techniques and the causes of amplitude and
frequency modulation distortions are discussed using a two-way coaxial type
loudspeaker system. The distortion due to amplitude modulation is caused by
the dependence of the radiation efficiency of the high frequency driver on
the displacement of the diaphragm of the low frequency driver. The
distortion due to frequency modulation seems to be produced when the high
frequency sound has a non-zero particle velocity in the axis direction at
the surface of the low frequency driver's diaphragm. The symmetry of the
sidebands of the summed modulation distortion (intermodulation distortion)
indicates that the amplitude and frequency modulation distortions are 90 deg
out of phase with each other.

Analysis of the Nonrigid Behavior of a Loudspeaker Diaphram Using Modal
Analysis 794397 bytes (CD aes11)
Author(s): Struck, Christopher J.
Publication: Preprint 2779; Convention 86; March 1989
Abstract: The behavior of a loudspeaker diaphragm beyond the piston range of
operation has previously only been investigated using analytic techniques
such as the Finite Element Method. An experimental method, Modal Analysis,
is presented that allows a model to be developed from actual measurements.
Previous problems in the measurement technique are overcome by the use of a
non-contacting laser transducer. A step by step analysis of a typical driver
is shown. After developing the modal model, it is possible to simulate
structural modifications and to study the dynamic system response. Special
application software is used for the measurement, analysis, and simulation.


Loudspeaker Large-Signal Limitations 791820 bytes (CD aes10)
Author(s): Small, Richard H.
Publication: Preprint 2102; Convention 1r; September 1984
Abstract: Some of the nonlinear and time-varying characteristics of dynamic
loudspeakers are quite different from those of other audio components. These
must be understood for the successful design of loudspeakers intended for
high sound reproduction levels. Selected nonlinear mechanisms and related
distortions are discussed, together with techniques for measuring important
driver large-signal parameters.

Improving Loudspeaker Performance for Active Noise Control Applications
1128840 bytes (CD aes6)
Author(s): Lane, Steven A.; Clark, Robert L.
Publication: Volume 46 Number 6 pp. 508·519; June 1998
Abstract: Actuator performance plays an important part in active noise and
acoustic control. The loudspeakers that are normally used as actuators in
many active noise and acoustic control applications add significantly to the
dynamics of the control loop and can be detrimental to the controller's
performance. By compensating a loudspeaker with a technique similar to
motional feedback, the loudspeaker performance is enhanced for applications
such as control of acoustic enclosures. A method to compensate a loudspeaker
easily and reliably in order to approximate constant volume velocity
behavior over the piston-mode frequency range is presented and demonstrated.
This decouples the actuator from the system being controlled and reduces the
impact of the loudspeaker's dynamics over the control bandwidth.
Experimental results of the proposed method using a 5-in (127-mm)
loudspeaker are included.

A Comparison of Three Methods of Measuring the Volume Velocity of an
Acoustic Source 1187730 bytes (CD aes5)
Author(s): Anthony, D. K.; Elliott, S. J.
Publication: Volume 39 Number 5 pp. 355·366; May 1991
Abstract: Measurement of the volume velocity of an acoustic source allows
the acoustic transfer impedance seen by the source and its acoustic power
output to be determined. An investigation of three sources is described
whose volume velocity can be determined in different ways: using laser
velocimetry, using measurement of the internal source pressure, and using a
moving-coil loudspeaker as an output transducer (Salavaís method). Practical
implementation of each method is discussed. Using laser velocimetry as a
reference measurement, the accuracy of the other two sources is determined.
The total harmonic distortion at the acoustic output is also measured.
Salavaís method is shown to be superior in both respects. Example
measurements of acoustic transfer impedance within a duct and in a
well-damped room demonstrate the use of such sources as measurement tools.
The former is shown to adhere well to theoretical predictions. Preliminary
experiments are also reported concerning the practical measurement of
acoustic power output, and the use of this measurement to maximize the
acoustic power absorption of the source when exposed to an external sound
field.

Investigation of the Nonrigid Behavior of a Loudspeaker Diaphragm Using
Modal Analysis 745135 bytes (CD aes5)
Author(s): Struck, Christopher J.
Publication: Volume 38 Number 9 pp. 667·675; September 1990
Abstract: The behavior of a loudspeaker diaphragm beyond the piston range of
operation is usually investigated using analytic techniques such as the
finite-element method. An experimental method, modal analysis, is presented,
which allows a model to be developed from actual measurements. Previous
problems in the measurement technique are overcome by the use of a
noncontacting laser transducer. A step by step analysis of a typical driver
is shown. After the modal model has been developed it is possible to
simulate structural modifications and to study the dynamic system response.
Special application software is used for the measurement, analysis, and
simulation.


The Development of a Sandwich-Construction Loudspeaker System 1816043 bytes
(CD aes3)
Author(s): Barlow, D. A.
Publication: Volume 18 Number 3 pp. 269·281; June 1970
Abstract: The development of a complete loudspeaker system is described,
based on moving-coil loudspeakers with cones of sandwich construction of
immense rigidity. Piston action is obtained over a wide range. Other
features are described, such as the unique construction of the cabinet,
which reduces `boxy' coloration.

Fundamentals of Modern Audio Measurement 2940094 bytes (CD aes17)
Author(s): Cabot, Richard C.
Publication: Paper MOA-02; Conference: AES UK Conference: The Measure of
Audio (MOA); April 1997
Abstract: Fundamental concepts in testing audio equipment are reviewed,
beginning with an examination of the various equipment architectures in
common use. Several basic analog and digital audio measurements are
described. Trade-offs inherent in the various approaches, the technologies
used, and its limitations are discussed. Novel techniques employing
multitone signals for fast audio measurements are examined and applications
of sampling frequency correction technology to this and conventional fft
measurements are covered. Synchronous averaging of ffts and the subsequent
noise reduction are demonstrated. The need for simultaneity of digital and
analog generation is presented using converter measurements as an example.

Real-Time Virtual Acoustics for 5.1 356578 bytes (CD aes16)
Author(s): Flanagan, Patrick; Dickins, Glenn; Layton, Leonard
Publication: Paper 16-012; Conference: The AES 16th International
Conference: Spatial Sound Reproduction; April 1999
Abstract: A large body of knowledge exists for 3-D acoustical simulation
over loudspeaker arrays. These techniques can be used for generating
surround material for the 5.1 loudspeaker format. Using such tools, the
mixing process is replaced by the concept of creating virtual acoustical
simulations for which the 5.1 loudspeaker array is the target reproduction
array.
Comparison of Nonlinear Distortion Measurement Methods 1498614 bytes (CD
aes16)
Author(s): Cabot, Richard C.
Publication: Paper 11-007; Conference: The AES 11th International
Conference: AES Test & Measurement Conference; May 1992
Abstract: Several techniques are currently in use for measuring distortion
of audio equipment. These include THD, SMPTE intermodulation, difference
frequence intermodulation, and DIM (sinewave-squarewave combination). A new
technique is proposed which uses a relatively large number of sinewaves to
effect complex intermodulation products across the entire audio band. This
paper compares the various methods, both theoretically and practically.
Examples of measurements on several test circuits are presented to
illustrate the results.


Subjectively Perceived Sound Quality in Audio Systems as a Function of
Distribution and Number of Loudspeakers Used in Playback 1118449 bytes (CD
aes15)
Author(s): Kristoffersen, Rune; Kleiner, Mendel; Västfjäll, Daniel
Publication: Preprint 4876; Convention 106; May 1999
Abstract: Many home stereo systems are currently being upgraded to some form
of surround sound systems in order to obtain a better listening experience.
It is obvious that the sound quality obtained in the use of such systems
depends on the quality of the speakers as well as the properties of the
room. In this paper results are presented from a pilot study on the
subjective preference of non-linear distortion versus playback mode of
conventional stereo recordings. An auralization approach to the evaluation
of distortion characteristics of loudspeakers has been used for the first
time. Sound files have been created which were subject to three different
distortion generating non-linearities. The resulting sound files were then
convolved by the proper impulse responses of a simulated anechoic room and a
simulated living room using three different loudspeaker configurations. The
resulting binaural signals were played back via low distortion electrostatic
headphones in listening tests in order to investigate the relationship
between distortion and spatial distribution of sound. Results indicate that
some non-linear distortion is preferred and that surround sound allows less
stringent distortion requirements for the loudspeakers than mono or stereo.

Distortion Mechanisms of Distributed-Mode Loudspeakers (Compared with
Direct Pistonic Radiators; Modeling, Analysis, and Measurement) 811412 bytes
(CD aes14)
Author(s): Colloms, Martin; Gontcharov, Vladimir; Panzer, Joerg; Taylor,
Valerie
Publication: Preprint 4757; Convention 104; May 1998
Abstract: Acoustic radiation from a Distributed Mode Loudspeaker (DML)
results from low amplitude bending waves. Compared with the motor system of
a pistonic driver, the DML exciter is of subtly different design and
equivalent circuit with a different relationship to the radiating diaphragm.
In this paper, loudspeaker distortions are reviewed, the equivalent circuits
modeled and compared with the DML case, and the results for comparative
measurements are presented.

Sound Reproduction Applications with Wave-Field Synthesis 1232332 bytes (CD
aes14)
Author(s): Boone, Marinus M.; Verheijen, Edwin N. G.
Publication: Preprint 4689; Convention 104; May 1998
Abstract: Wave field synthesis (WFS) enables the reproduction of sound
fields in a principally much better way than other (multichannel)
reproduction systems do. Because of the spatial properties of the reproduced
sound field, a so-called volume solution is obtained. Emphasis is given to
practically optimized recording and reproduction techniques and
compatibility, forming the basis for applications that can benefit from the
spatial quality of WFS.

Fundamentals of Modern Audio Measurement 3367120 bytes (CD aes14)
Author(s): Cabot, Richard C.
Publication: Preprint 4604; Convention 103; September 1997
Abstract: Fundamental concepts in testing audio equipment are reviewed,
beginning with an examination of the various equipment architectures in
common use. Several basic analog and digital audio measurements are
described. Tradeoffs inherent in the various approaches, the techniques
used, and its limitations are discussed. Novel techniques employing
multitone signals for fast audio measurements are examined and applications
of sampling frequency correction technology to this and convention fat
measurements are covered. Synchronous averaging of fits and the ;subsequent
noise reduction are demonstrated. The need for simultaneity of digital and
analog generation is presented using converter measurements as an example.


Aspects of MLS Measuring Systems 1083800 bytes (CD aes12)
Author(s): Vanderkooy, John
Publication: Preprint 3398; Convention 93; October 1992
Abstract: A maximum-length sequence (MLS) has mathematical properties that
make it very useful as an excitation signal for measurement in audio and
acoustics. This paper explores the pathology of MLS systems when there is
distortion of various kinds. The resulting artefacts can falsify a
reverberation plot, reduce the distortion immunity of the measurement
system, and give rise to spurious reflections in the impulse response, to
name a few negative aspects. On the other hand, MLS systems can also allow
the determination of the total distortion of an electroacoustic system when
excited by a signal of any desired spectrum, and sensitive tests for
determining the presence of distortion are possible due to the time-domain
separation of linear and nonlinear components.

Constant Component of the Loudspeaker Diaphragm Displacement Caused by
Non-Linearities 375516 bytes (CD aes11)
Author(s): Dobrucki, A.
Publication: Preprint 2577; Convention 84; March 1988
Abstract: The independent of time component of displacement appears, apart
from increase of even harmonics, if the most significant nonlinear
characteristics of loudspeaker i.e. nonlinear stiffness of suspensions and
nonhomogeneous magnetic field in the gap are nonsymmetrical in relation to
the rest position of the diaphragm and voice coil. In some conditions, the
value of this displacement can be so large, that the normal action of the
loudspeaker will be disturbed. In the paper, the phenomenon is studied both
theoretically and experimentally. It is proven that dependence of the
constant component of frequency of modulation is different in the case of
nonsymmetrical stiffness of suspension than in the case of unhomogenous
magnetic field in the gap. This fact can be used to identify the reason for
the appearance of constant component, its minimization and decreasing of
harmonic content.

A Standard Monitor Loudspeaker Used as a Reference for Digital Audio
Productions in Studios with Different Acoustic Properties 4111561 bytes (CD
aes18)
Author(s): Goldstein, Samuel H.
Publication: Preprint 1968; Convention 73; March 1983
Abstract: Loudspeakers having an ideal frequency response in an anechoic
room sound different in monitor rooms having other acoustic properties. In
these rooms, which are not ideal from the acoustical point of view, the
sound is reflected to the listener with frequency responses differing so
much from one another that the first (nonreflecting) sound component is
received with an ideal response, whereas the delayed ground-reflected sound
features a bass boost, the sound reflected by the ceiling makes an extremely
present impression and in the lateral reflections the lower midrange is
missing. These great deviations of the polar pattern are due to the
frequency differences. This paper describes an active monitor loudspeaker
system having a practically uniform polar response over the total listening
range.

Phase Distortion and Phase Equalization in Audio Signal Processing·A
Tutorial Review 3113054 bytes (CD aes10)
Author(s): Preis, Douglas
Publication: Preprint 1849; Convention 70; October 1981
Abstract: Various definitions and measures of phase distortion are reviewed
beginning with first principles. Numerous representative examples are
included indicating quantitative amounts of phase distortion produced by
microphones, loudspeakers, coaxial cables, anti-alias filters and magnetic
recording. The effects of phase distortion on time-domain performance are
discussed. A frequency-dependent tolerance on group delay distortion is
developed based on seven different perceptual studies and compared with some
representative measurements. New and complementary experiments are proposed
to assess further the perceptual significance of phase distortion in music
reproduction. Methods of phase equalization and phase equalizer design are
presented. A new time-frequency display, showing both the location of a
signal in time and its frequency spread, is introduced which provides a more
unified view of time-domain and frequency-domain interrelationships.

A Revolutionary 3-D Interferometric Vibrational Mode Display 1329271 bytes
(CD aes9)
Author(s): Bank, G.; Hathaway, G. T.
Publication: Preprint 1658; Convention 66; May 1980
Abstract: When the beam from a laser vibration interferometer is optically
raster scanned over a vibrating surface a phase sensitive detector provides
velocity information at any phase of the motion. This data is digitally
processed and hard copy print gives a 3-D isometric view of the complete
vibrating surfaces of the test object frozen in time.

A Comparison of Nonlinear Distortion Measurement Methods 2000998 bytes (CD
aes9)
Author(s): Cabot, Richard C.
Publication: Preprint 1638; Convention 66; May 1980
Abstract: Several techniques are currently in use for measuring distortion
of audio equipment. These include THD, IM-difference frequency, sine-square,
random noise, and recently a three-tone intermodulation distortion test has
been proposed. This paper compares the various methods, both theoretically
and practically. The effects of changing the test frequencies used in each
test on its sensitivity and practicality are discussed. It is found that
this yields a significant improvement in sensitivity to many forms of
distortion.


Time Distortion in Loudspeakers 553257 bytes (CD aes9)
Author(s): Lian, R.
Publication: Preprint 1207; Convention 56; March 1977
Abstract: From the fundamental pressure/time functions, this paper describes
the different types of distortion appearing in loudspeakers. Special
attention is paid to time and pitch distortion. Different mechanical
solutions in loudspeaker driver design, and their influence on
magnitude/time distortion are discussed. Some preliminary conclusions are
drawn, though the paper proposes more questions than answers.

Swept Electroacoustic Measurements of Harmonic Distortion,
Difference-Frequency and Intermodulation Distortion 1271330 bytes (CD aes8)
Author(s): Thomsen, Carsten; Møller, Henning
Publication: Preprint 1068; Convention 52; October 1975
Abstract: In music, many frequencies occur simultaneously, therefore
distortion tests which are relevant to music must be carried out using more
than one frequency. A system is introduced for automatic swept measurement
of harmonic distortion, difference frequency and intermodulation distortion
in the range 2 Hz-200 kHz. The relationship of high-frequency (up to 200
kHz) IM and difference-frequency distortion to transient intermodulation
(TIM) is explored. The system consists of a sweeping two-tone generator and
a heterodyne analyzer phase-locked to the selected distortion components up
to the fifth order. Typical dynamic range permits measurements down to 0.01
% in the harmonic and difference-frequency modes, and to 0.001% in the IM
mode.

Intermodulation Distortion Listening Tests 359592 bytes (CD aes8)
Author(s): Fryer, P. A.
Publication: Preprint L-10; Convention 50; March 1975
Abstract: It is fairly simple to measure the amount of intermodulation
distortion produced by loudspeakers, but it is more difficult to find out
how much of this kind of distortion is found objectionable (or just
detectable) when masked by music. It is made more difficult by the fact that
this has to be done in the absence of other kinds of distortion such as
harmonic and transient intermodulation distortion. In order to measure the
effects of intermodulation distortion, a 'black box' was built which was
capable of generating a known and controllable percentage of pure
intermodulation distortion, and then listening tests were held at different
sound pressure levels with different kinds of music with several speakers
and listeners. The results show that intermodulation distortion is masked to
a large extent by music but it can be easily detected when pure tones are
used.

Threshold of Phase Detection by Hearing 1042299 bytes (CD aes8)
Author(s): Hansen, Villy; Madsen, Erik Rørbaek
Publication: Preprint C-1; Convention 44; March 1973
Abstract: For years, the ability to detect phase distortion in musical
signals has been a much debated question. Research has been carried out for
the purpose of finding a suitable complex signal whose different frequency
components could be changed in phase without altering the amplitude spectrum
of the signal. Subjective listening tests have been made on a number of
listeners in order to find the threshold of phase detection. the test was
carried out with high-fidelity headphones and high-fidelity loudspeakers in
a semi-reverberant room. It is proven experimentally that phase detection
increases in a reverberant room and when using loudspeakers having poor
transfer characteristics. It is demonstrated that the ear prefers the
frequency content in the negative pressure transient fronts. This
demonstrates the importance of absolute phase, for which reason there should
be standardization of phase conditions from sound source to sound
reproducer.

Modulation Distortion in Loudspeakers 593264 bytes (CD aes7)
Author(s): Klipsch, Paul W.
Publication: Preprint 562; Convention 34; April 1968
Abstract: When comparing 2 loudspeakers, one with direct radiator bass
system and the other with horn loaded bass, a subjective judgment was that
the one with the horn loaded bass is ·cleaner.· Both speakers were by the
same manufacturer. Various tests were applied and by process of elimination
it appears the difference in listening quality is due to frequency
modulation distortion. Beers and Belar analyzed this form of distortion in
1943, but since that time the effect has been almost ignored. Now, with
amplifiers and source material reaching new lows in distortion, differences
between good loudspeakers begin to appear significant. The mathematical
analysis has been reviewed, and measurements have been made using a spectrum
analyzer. These have been correlated with listening tests by preparing tapes
of oscillator tones and music with and without a low frequency source to
produce frequency modulation distortion. The spectrum analyses corroborate
the mathematical analysis and the listening tests offer a subjective
evaluation. The conclusion is that frequency modulation in loudspeakers
accounts in large measure for the masking of ·inner voices.· As Beers and
Belar put it, ·The sound is just not clean.· Reduction of diaphragm
excursions at lower frequencies reduces FM distortion. Horn loading,
properly applied, offers the greatest reduction, while simultaneously
improving bass power output capability. Tentatively it is wondered if FM
distortion in loudspeakers may be the last frontier in loudspeaker
improvement.

Distortion Measurements of High-Frequency Loudspeakers 2872873 bytes (CD
aes7)
Author(s): Kantrowitz, Philip
Publication: Preprint 218; Convention 13; October 1961
Abstract: The relative importance of linearity and distortion in
high-frequency loudspeakers has been investigated. Hemispherical direct
radiators, conical direct radiators, a ribbon horn, dynamic horns, a
single-ended and a push-pull electrostatic speaker were evaluated for
frequency response, non-linear distortion and directionality. Quadratic and
cubic non-linear distortion terms are present in high-frequency
loudspeakers. The maximum cubic CCIF non-linear distortion in horns is
greater than that found for the direct radiator and push-pull electrostatic
types. Smoothness of response, directional characteristics and extent of
frequency range are generally more significant than distortion in the
classification of the ·listenability· of the high-frequency loudspeaker.
Subjective listening tests, however, indicate that total CCIF non-linear
distortion above approximately 3% is objectionable. In a complete speaker
system, the capabilities of a superior high-frequency loudspeaker may be
severely limited or altered due to the selection of an improper cross-over
netowrk or the use of inferior middle and low range speaker units.
Introductory Remarks to the Session on Acoustics in Oceanographic Research,
and Sound - The Test Probe to Sense the Ocean 590514 bytes

Fundamentals of Modern Audio Measurement 10045860 bytes (CD aes6)
Author(s): Cabot, Richard C.
Publication: Volume 47 Number 9 pp. 738·744, 746-762; September 1999
Abstract: Fundamental concepts in testing audio equipment are reviewed,
beginning with an examination of the various equipment architectures in
common use. Several basic analog and digital audio measurements are
described. Tradeoffs inherent in the various approaches, the technologies
used, and their limitations are discussed. Novel techniques employing
multitone signals for fast audio measurements are examined and applications
of sampling frequency correction technology to this and conventional FFT
measurements are covered. Synchronous averaging of FFTs and the subsequent
noise reduction are demonstrated. The need for simultaneity of digital and
analog generation is presented using converter measurements as an example.

Fifty Years of Loudspeaker Developments as Viewed Through the Perspective
of the Audio Engineering Society 3982910 bytes (CD aes6)
Author(s): Gander, Mark R.
Publication: Volume 46 Number 1/2 pp. 43-58; January 1998
Abstract: An exhaustive review of over 450 AES Journal loudspeaker papers
and other select references is presented and categorized by subject area.
The names and affiliations of the authors are included. Perspective is given
on the technical significance, degree of influence, and historical context
of the contributions and contributors. Except where otherwise noted, all
references are from the Journal of the Audio Engineering Society and, where
applicable, the volumes of the AES Loudspeakers anthology.

Aspects of MLS Measuring Systems 1225899 bytes (CD aes5)
Author(s): Vanderkooy, John
Publication: Volume 42 Number 4 pp. 219·231; April 1994
Abstract: A maximum-length sequence (MLS) has mathematical properties that
makeit very useful as an excitation signal for measurement in audio and
acoustics. The pathology of MLS systems when there is distortion of various
kinds is explored. The resulting artifacts can falsify a reverberation plot,
reduce the distortion immunity of the measurement system, and give rise to
spurious reflections in the impulse response, to name a few negative
aspects. On the other hand, MLS systems can also allow the determination of
the total distortion of an electroacoustic system when excited by a signal
of any desired spectrum, and sensitive tests for determining the presence of
distortion are possible due to the time-domain separation of linear and
nonlinear components.


Direct Low-Frequency Driver Synthesis from System Specifications 1144589
bytes (CD aes4)
Author(s): Keele, Jr., D. B.
Publication: Volume 30 Number 11 pp. 800·814; November 1982
Abstract: The usual procedure for direct-radiator low-frequency loudspeaker
system design leads to the calculation of the driver's fundamental
electromechanical parameters by an intermediate specification of the
Thiele-Small parameters. A reformulation of the synthesis procedure to
eliminate the intermediate Thiele-Small calculation leads to a set of
equations that yield the driver's electromechanical parameters directly from
the system specifications. These equations reveal some moderately surprising
relationships when the different system types (closed box, fourth-order
vented box, and sixth-order vented box) are compared. For example, for a
specified low-frequency cutoff f(3), midband efficiency, and driver size the
fourth-order vented-box driver is found to be roughly three times more
expensive (judged on the amount of magnet energy required) than the
closed-box driver. Conversely for a given f(3), enclosure volume V(B),
maximum diaphragm excursion X(max), and acoustic power output P(AR) the
fourth-order vented-box driver is some five times cheaper than the
closed-box driver. It is also found that for direct-radiator systems in
general, specified f(3), V(B), X(max), and P(AR) lead to the total moving
mass M(MS) depending inversely on the sixth power of the cutoff frequency,
that is, a one-third-octave reduction in f(3) results in a fourfold increase
in mass. Furthermore, the same conditions reveal that the sixth-order
vented-box driver moving mass is some 42 times lighter than that of the
closed-box driver, providing the same midband acoustic output and f(3). If
cone area and efficiency are held constant, the direct-radiator system
driver actually gets less expensive as the low-frequency limit is extended.

Phase Distortion and Phase Equalization in Audio Signal Processing·A
Tutorial Review 2705909 bytes (CD aes4)
Author(s): Preis, D.
Publication: Volume 30 Number 11 pp. 774·794; November 1982
Abstract: Various definitions and measurements of phase distortion are
reviewed beginning with first principles. Numerous representative examples
are included, indicating quantitative amounts of phase distortion produced
by microphones, loudspeakers, coaxial cables, antialias filters, and
magnetic recording. The effects of phase distortion on time-domain
performance are discussed. A frequency-dependent tolerance on group-delay
distortion is developed based on seven different perceptual studies and
compared with some representative measurements. New and complementary
experiments are proposed to assess further the perceptual significance of
phase distortion in music reproduction. Methods of phase equalization and
phase equalizer design are presented. A new time-frequency display, showing
both the location of a signal in time and its frequency spread, is
introduced, which provides a more unified view of time-domain and
frequency-domain interrelationships.


Modulation Distortion in Loudspeakers: Part 3 187326 bytes (CD aes3)
Author(s): Klipsch, Paul W.
Publication: Volume 20 Number 10 pp. 827·828; December 1972
Abstract: Distortion in loudspeakers is shown to be nearly proportional to
power output. Typically a plot of log distortion versus dB output shows a
1:1 relation. In one sample ooudspeaker the slope of the distortion versus
output curve was in excess of 45 degrees. Comparison is shown between a
direct radiator of 20-cm (8-in) diameter, one of 30-cm (12-in) diameter, and
a high-efficiencØ horn of 0.45 m/3 (16 ft/3). At 95-dB sound pressure level
output measured at 61 cm (2 ft) the 12-cm cone showed 18% (·15 dB ref 100%),
the 30-cm cone showed 6% (·25 dB ref 100%), and the horn showed 0.8% (·42 dB
ref 100%). Each curve of distortion versus output shows a slope of at least
45 degrees.

Comments on "Modulation Distortion in Loudspeakers" and Author's Reply
259555 bytes (CD aes3)
Author(s): Cole, Sr., T. S.; Klipsch, Paul
Publication: Volume 17 Number 4 pp. 448-449; August 1969
Abstract: Not available.

Acoustical Measurements by Time Delay Spectrometry 2331867 bytes (CD aes2)
Author(s): Heyser, Richard C.
Publication: Volume 15 Number 4 pp. 370·382; October 1967
Abstract: A new acoustical measurement technique has been developed that
provides a solution for the conflicting requirements of anechoic spectral
measurements in the presence of a reverberant environment. This technique,
called time delay spectrometry, recognizes that a system-forcing function
linearly relating frequency with time provides spatial discrimination of
signals of variable path length when perceived by a frequency-tracking
spectrum analyzer.

Epilogue on Measurements 222950 bytes (CD aes2)
Author(s): Cooper, Duane H.
Publication: Volume 12 Number 4 pp. 344, 346; October 1964
Abstract: Not available.
Distortion of High-Frequency Loudspeakers 770716 bytes (CD aes2)
Author(s): Kantrowitz, Philip
Publication: Volume 10 Number 4 pp. 310·317; October 1962
Abstract: The relative importance of linearity and distortion in
high-frequency loudspeakers was investigated. Hemispherical direct
radiators, conical direct radiators, a ribbon horn, dynamic horns, a
single-ended and a push-pull electrostatic speaker were evaluated for
frequency response, nonlinear distortion and directionality. Quadratic and
cubic non-linear distortion terms were found to be present in high-frequency
loudspeakers. The maximum cubic CCIF nonlinear distortion in horns was
greater than that found for the direct radiator and push-pull electrostatic
types. Smoothness of response, directional characteristics and extent of
frequency range were generally more significant than distortion in the
classification of the ·listenability· of the high-frequency loudspeaker.
Subjective listening tests, however, indicated that total CCIF non-linear
distortion above approximately 3% is objectionable. It was found that in a
complete speaker system, the capabilities of a superior high-frequency
loudspeaker may be severely limited or altered due to the selection of an
improper cross-over network or the use of inferior middle and low range
speaker units.

enjoy! ;-)

[Arny Krueger]

"Bob Cain" > wrote in message

> Arny Krueger wrote:
>
>
>> Doppler has not escaped the attention of the technical community.
>> There are a number of JAES papers about it.

> Citations, please.


The Audibility of Doppler Distortion in Loudspeakers 1035944 bytes (CD
aes10)
Author(s): Allison, Roy; Villchur, Edgar
Publication: Preprint 1844; Convention 70; October 1981
Abstract: Although Doppler distortion in loudspeakers has been often viewed
with alarm since Beers and Belar described it in 1943, the question of its
significance in music reproduction has not yet been answered. In this study
the audibility of Doppler distortion in simple direct radiators is
investigated theoretically (by analogy to tape-machine flutter and by
analysis of blind listening-room acoustic effects), and experimentally (by
double-blind listening tests). The analysis predicts Doppler inaudibility
for any practical cone velocity, and the experimental results provide
confirming evidence.

The Audibility of Doppler Distortion in Loudspeakers 1059616 bytes (CD
aes10)
Author(s): Allison, Roy; Villchur, Edgar
Publication: Preprint 1769; Convention 69; May 1981
Abstract: Although Doppler distortion in loudspeakers has been often viewed
with alarm since Beers and Belar described it in 1943, the question of its
significance in music reproduction has not yet been answered. In this study
the audibility of Doppler distortion in simple direct radiators is
investigated theoretically (by analogy to tape-machine flutter and by
analysis of listening room acoustic effects), and experimentally (by
double-blind listening tests). The analysis predicts Doppler inaudibility
for any practical cone velocity, and the experimental results provide
confirming evidence.

On the Magnitude and Audibility of FM Distortion in Loudspeakers 732451
bytes (CD aes4)
Author(s): Allison, Roy; Villchur, Edgar
Publication: Volume 30 Number 10 pp. 694·700; October 1982
Abstract: Beers and Belar, in their 1943 paper on Doppler effect in
loudspeakers, recognized and pointed out limitations in the scope of their
analysis. They also suggested simple methods for keeping FM distortion
products below the level of audibility, such as dividing the spectrum among
at least two drivers. Recent work is described which extends Beers and
Belar's analysis along lines they suggested, and which, by means of
double-blind listening tests, provides confirming evidence that Doppler
distribution in practical multidriver systems is indeed inaudible.

Simulation and Investigation of Doppler Distortion 402761 bytes (CD aes9)
Author(s): Fryer, P. A.
Publication: Preprint 1197; Convention 56; March 1977
Abstract: Doppler distortion audibility has been assessed using two delay
lines. The clock frequency of one is varied in accordance with the Doppler
formula and the other is the idle of the first. Their subtracted outputs,
therefore, give a measure of the simulated Doppler distortion present.
Progressive reduction of the simulation on A-B tests gives lowest detectable
levels.

Implementing Doppler Shifts for Virtual Auditory Environments 1062709 bytes
(CD aes14)
Author(s): Strauss, Holger
Publication: Preprint 4687; Convention 104; May 1998
Abstract: A listening test has shown that the plausibility of virtual
auditory environments can be increased significantly when Doppler shifts are
adequately emulated. A simple sound-field model capable of calculating the
necessary auralization parameters for moving sound sources and listeners in
real-time applications is presented. Signal processing algorithms for
auralizing Doppler shifts are discussed.

Loudspeaker Distortion with Low-Frequency Signals 1222990 bytes (CD aes3)
Author(s): Harwood, H.D.
Publication: Volume 20 Number 9 pp. 718·728; November 1972
Abstract: Three differing forms of distortion, which are associated with
low-frequency signals in loudspeakers, are investigated. It is shown that
distortion due to the Doppler effect can be compared with that due to wow
and flutter in recording machines, and subjective data obtained for this
purpose can be applied to loudspeakers. Generalized design limits for
loudspeakers are calculated. In loudspeakers designed to reproduce low
frequencies, the voice coil is made longer than the magnetic field. At low
frequencies, when the amplitude of vibration of the cone exceeds the
difference in length, it is shown that instead of the peaks of the waveform
being clipped, expansion of the input-output curve takes place. This effect,
with its associated distortion, can be compensated by employing an
appropriate nonlinear suspension, and thus a much greater useful output can
be obtained than by using a linear suspension. Finally, a vented cabinet is
often used to reduce the magnitude of the undesirable effects previously
mentioned as well as to extend the bass response. However, a vented cabinet
is a resonant system and high sound pressures and particle velocities are
produced in the vent. These are liable to give rise to distortion from the
inherent nonlinearity in the air and from turbulence at the orifice and in
the pipe. Existing data ae used to estimate the sound levels which may be
generated in a typical listening room before distortions from any of these
causes are audible. It is also shown that this form of distortion is not a
troublesome factor in the design of studio monitoring loudspeakers.

Magnitude Estimation of Sound Source Speed 115837 bytes (CD aes15)
Author(s): Ericson, Mark A.
Publication: Preprint 5209; Convention 109; September 2000
Abstract: Linear motion of a harmonic sound source was simulated for various
trajectory paths. The acoustic signal was processed with frequency and
intensity changes because of Doppler shifts in frequency, overall intensity
changes, and atmospheric absorption. While listening to these sounds over
headphones, four participants were asked to make magnitude estimations of
the sound source speed under various combinations of motion effects. The
frequency and intensity changes were found to contribute to the ability of
the listeners to judge sound source speed. Inclusion of these motion
attributes produced a veridical simulation of sound source motion.

On the Doppler Distortion in Loudspeakers 867677 bytes (CD aes3)
Author(s): Braun, S.
Publication: Volume 21 Number 3 pp. 185·187; April 1973
Abstract: A short review of Doppler distortion is given. An experimental
setup isolating this effect from nonlinearity-induced distortion is
described and its feasibility tested.

Prediction of Speaker Performance at High Amplitudes 591237 bytes (CD
aes18)
Author(s): Klippel, Wolfgang
Publication: Preprint 5418; Convention 111; December 2001
Abstract: A new method is presented for the numerical simulation of the
large signal performance of drivers and loudspeaker systems. The basis is an
extended loudspeaker model considering the dominant nonlinear and thermal
effects. The use of a two-tone excitation allows the response of
fundamental, DC-component, harmonics, and intermodulation components to be
measured as a function of frequency and amplitude. After measurement of the
linear and nonlinear parameters, the electrical, mechanical, and acoustical
state variables may be calculated by numerical integration. The relationship
between large signal parameters and non-linear transfer behavior is
discussed by modeling two drivers. The good agreement between simulated and
measured responses shows the basic modeling, parameter identification, and
numerical predictions are valid even at large amplitudes. The method
presented reduces time-consuming measurements and provided essential
information for quality assessment and diagnosis. The extended loudspeaker
model also allows prediction of design changes on the large signal
performance by changing the model parameters to reflect the driver design
changes. The incorporation of nonlinear parameters into the loudspeaker
model allows for optimization in both the small and large signal domains by
model prediction.

Multitone Testing of Sound System Components·Some Results and Conclusions,
Part 1: History and Theory 2073763 bytes (CD aes18)
Author(s): CZERWINSKI, EUGENE; VOISHVILLO, ALEXANDER; ALEXANDROV, SERGEI;
TEREKHOV, ALEXANDER
Publication: Volume 49 Number 11 pp. 1011-1048; November 2001
Abstract: An historical retrospective analysis of the measurement of
nonlinearities in audio is carried out. A quantitative analysis of the
responses of various nonlinear systems (theoretical and experimental) to a
multitone signal is made, and multitone testing is compared to conventional
harmonic and intermodulation measurements. The multitone test provides more
accurate information about the behavior of nonlinear systems when compared
to standard harmonic, two-tone intermodulation, and total harmonic
distortion measurements. Modeling of the nonlinear reaction of various sound
system components to a multitone signal is described.

Doppler-Type Organ Tone Cabinet 295593 bytes (CD aes2)
Author(s): Machanian, William V.
Publication: Volume 10 Number 3 pp. 216·218; July 1962
Abstract: The problems confronting the designer of organ tone cabinets are
analyzed. Two different requirements must be satisfied for a Doppler-type
tone cabinet design. One requirement is the faithful reproduction of the
generated musical tones with a minimum of distortion. Th'second requirement
relates to Doppler modulation of the musical signal to provide what is
called a ·vibrato· effect.

Subwoofer Performance for Accurate Reproduction of Music 1682416 bytes (CD
aes11)
Author(s): Fielder, Louis D.; Benjamin, Eric M.
Publication: Preprint 2537; Convention 83; October 1987
Abstract: The spectra and maximum output levels for accurately reproducing
low frequency musical signals are determined from published research and new
measurements. Analysis of commercial recording shows substantial musical
information in the octave from 32 to 16 Hz and some down to 12 Hz.
Psychoacoustic data are used to establish to what degree errors (such as
THD, FM distortion, modulation noise, and bandwidth limits) are perceptible.
Criteria are set for proper subwoofer performance at peak levels of 110 dB
SPL.

Subwoofer Performance for Accurate Reproduction of Music 1546477 bytes (CD
aes4)
Author(s): Fielder, Louis D.; Benjamin, Eric M.
Publication: Volume 36 Number 6 pp. 443·456; June 1988
Abstract: The spectra and the maximum output levels for accurately
reproducing low-frequency musical signals are determined from published
research and new measurements. Analysis of commercial recordings shows
substantial musical information in the octave from 32 to 16 Hz and some down
to 12 Hz. Psychoacoustic data are used to establish to what degree errors
(such as total harmonic distortion, FM distortion, modulation noise, and
bandwidth limits) are perceptible. Criteria are set for proper subwoofer
performance at peak sound pressure levels of 110 dB.

Doppler Distortion in Loudspeakers 763066 bytes (CD aes8)
Author(s): Moir, James
Publication: Preprint 925; Convention 46; September 1973
Abstract: In 1942 two R.C.A. engineers, G.L. Beers ahd H. Belar, drew
attention to the presence of a form of distortion in loudspeaker
reproduction not previously identified. It is the result of modulation of
the frequency of one signal by the frequency of a second signal
simultaneously applied. Because of the difficulties in obtaining reliable
quantitative data on the extent of this distortion, its existence has been
challenged by many writers and though its presence has been conclusively
proved by Klipsch, More, Braun and others, its importance may still be in
doubt. It is the purpose of the present contribution to describe some simple
techniques for the segregation and measurement of this form of distortion
and to provide data on its magnitude in some typical commercial speaker
systems.

Moving Boundary Condition and Nonlinear Propagation as the Sources of
Nonlinear Distortion in Loudspeakers 596452 bytes (CD aes12)
Author(s): Zóltogórski, Bronislaw
Publication: Preprint 3510; Convention 94; March 1993
Abstract: Two natural phenomena connected with the excitation of acoustic
waves by moving the loudspeaker diaphragm are considered: 1) effect of a
moving boundary condition traditionally named the Doppler effect; and 2)
effect of nonlinear propagation of acoustic waves. In this paper, it is
shown that distortions caused by nonlinear propagation have negligible
magnitude; and that an improved expression for the coefficient of
Doppler-type distortions is derived. A concept of an anti-Doppler filter is
presented.

Moving Boundary Conditions and Nonlinear Propagation as Sources of
Nonlinear Distortions in Loudspeakers 614943 bytes (CD aes5)
Author(s): Zóltogórski, Bronislaw
Publication: Volume 41 Number 9 pp. 691·700; September 1993
Abstract: Two phenomena connected with the generation of acoustic waves by a
loudspeaker diaphragm are considered: 1) the effect of moving boundary
conditions, traditionally called the Doppler effect, and 2) the effect of
nonlinear acoustic wave propagation. It is shown that distortions caused by
moving boundary conditions are dominant in a low-frequency range. An
improved expression is derived for the coefficient of Doppler-type
distortions, and an idea for an anti-Dopper filter is presented.

The Mirror Filter·A New Basis for Linear Equalization and Nonlinear
Distortion Reduction of Woofer Systems 1459125 bytes (CD aes12)
Author(s): Klippel, Wolfgang
Publication: Preprint 3221; Convention 92; March 1992
Abstract: A new filter structure derived from the nonlinear differential
equation and switched into the electrical path enables the reduction of
nonlinear distortions of loudspeakers caused by displacement of varying
parameters (force factor, stiffness, and inductance) and Doppler effect.
Simultaneously, this filter is used for optimizing the linear frequency
response (resonance frequency and Q-factor) and for realizing an effective
protection against destruction. Unlike feedback systems, no permanent sensor
is required. To adjust the filter parameters to the actual loudspeaker
automatically, an iterative method is presented which is based on the
electrical or acoustical measurement of the overall transfer response. Both
the filter and the auxiliary systems for protection and adjustment are
implemented in a DSP 56001 and result in a self-learning distortion
reduction system. This system was tested on different loudspeakers. Results
are contrasted to the listening impression and possible consequences to
loudspeaker design are discussed.

The Mirror Filter·A New Basis for Reducing Nonlinear Distortion and
Equalizing Response in Woofer Systems 1289233 bytes (CD aes5)
Author(s): Klippel, Wolfgang
Publication: Volume 40 Number 9 pp. 675·691; September 1992
Abstract: A new filter structure, derived from the applicable nonlinear
differential equation and inserted in the signal path, reduced loudspeaker
nonlinear distortion caused by displacement-sensitive parameters (force
factor, stiffness, and inductance) and by the Doppler effect. This filter
can also be used for optimizing the linear frequency response (resonance
frequency and Q factor) and for protecting against mechanical damage. There
is no need for a permanent sensor, a requirement in feedback systems. To
adjust the filter parameters automatically to a particular loudspeaker, an
iterative method is presented, based on the electrical or acoustical
measurement of the overall transfer response. Both the filter and the
auxiliary systems for protection and adjustment are implemented in a DSP
56001 and result in a self-learning distortion-reduction system. The system
was tested on different loudspeakers, and the measurement results are
compared with listening impressions. The possible consequences in
loudspeaker design are discussed.

Frequency-Modulation Distortion in Loudspeakers (Reprint) 693548 bytes (CD
aes4)
Author(s): Beers, G.L.; Belar, H.
Publication: Volume 29 Number 5 pp. 320·326; May 1981
Abstract: As the frequency-response range of a sound-reproducing system is
extended, the necessity for minimizing all forms of distortion is
correspondingly increased. The part which the loudspeaker can contribute to
the overall distortion of a reproducing system has been frequently
considered. A type of loudspeaker distortion which has not received general
consideration is described. This distortion is a result of the
Doppler-effect and produces frequency modulation in loudspeakers reproducing
complex tones. Equations for this type of distortion are given. Measurements
which confirm the calculated distortion in several loudspeakers are shown.
An appendix giving the derivation of the equations is included.
Contactless Flaw Detection Based on the Doppler Effect 242797 bytes (CD
aes11)
Author(s): Cherek, B.; Armannson, J. H.; Delsanto, P. P.
Publication: Preprint 2785; Convention 86; March 1989
Abstract: A nondestructive flaw detection technique, based on a contactless
device is presented. To demonstrate its applicability, measurements have
been performed on several A1 plates before and after flawing them with one
or more scratches. A spectrum analysis shows a significant change in the
height of the odd harmonics, which increases with the number and size of the
scratches.

Automatic Vibration Analysis by Laser Interferometry 314875 bytes (CD
aes11)
Author(s): Wright, J. R.
Publication: Preprint 2889; Convention 88; March 1990
Abstract: A new measurement system for non-contact vibration analysis has
been developed, using the scanning laser interferometry method to measure
local velocities of a vibrating surface. The system can run as a fully
automated (unmanned) test, and has applications in structural or modal
analysis in fields as diverse as the motor industry, transducer design, or
building vibration measurement.

A Non-Linear Model of a Small Transducer 783682 bytes (CD aes17)
Author(s): Backman, Juha
Publication: Paper MAL-10; Conference: AES UK Conference: Microphones &
Loudspeakers, The Ins & Outs of Audio (MAL); March 1998
Abstract: The paper presents a model for an inherent distortion caused by
flow resistance modulation in small transducers. The distortion mechanisms
analysed here include the modulation of the transducer's moving mass, its
compliance, and the viscous damping. A numerical model is presented for
different forms of non-linearity, and examples indicating the significance
of the non-linear effects are computed.

Objective Characterization of Audio Sound Fields in Automotive Spaces
3625082 bytes (CD aes16)
Author(s): Kleiner, Mendel; Lindgren, Claes
Publication: Paper 15-007; Conference: The AES 15th International
Conference: Audio, Acoustics & Small Spaces; October 1998
Abstract: The properties of sound fields in cars are of great interest. A
considerable part of the daily noise exposure of many people is obtained
while driving. The car compartment today is also the primary music listening
environment for many people, and many people spend considerable amounts of
money on car audio equipment. Audio for the car environment requires
different engineering tradeoffs than for the home environment. The cognitive
aspect for car audio equipment may be larger than for domestic equipment.
The car is for many the most important status symbol. Also, the presence of
noise while listening to voice and music results in different system
criteria. Consequently, understanding the electroacoustics and room
acoustics of the car audio environment is important. Audio system design
criteria have to be set by and for measurements. Most conventional acoustic
measures are of interest in the car acoustics measurement but emphasis is
shifted to the sound pressure at the listener's position. The audio measures
have to be modified because of the special listening circumstance due to the
small size of the compartment. The field offers many opportunities for
further research in order to find objective measures that describe the
listening experience well.

Distortion from Boundary Layers 632495 bytes (CD aes14)
Author(s): Backman, Juha
Publication: Preprint 4619; Convention 103; September 1997
Abstract: The paper presents a model for an inherent distortion caused by
flow resistance modulation in small transducers. This type of distortion is
most significant near the resonance frequency of the transducer, and can be
an important factor in limiting the transducer performance. A numerical
model is presented for different forms of nonlinearity, and examples of the
nonlinear effects are computed.

A Reliable Method of Loudspeaker Rub and Buzz Testing Using Automated FFT
Response and Distortion Techniques 4029773 bytes (CD aes12)
Author(s): Groeper, Gregory G.; Blanchard, Mark A.; Brummett, Terry; Bailey,
Jeff
Publication: Preprint 3161; Convention 91; October 1991
Abstract: By utilizing modern DSP technology and FFT spectral analysis, and
by applying some aspects of human hearing and psychoacoustics, a reliable
method of rub and buzz distortion testing for loudspeakers can be devised
for a wide variety of engineering and production applications. Additionally,
test times can be radically reduced, thus contributing favorably to outside
noise rejection and a higher degree of repeatability. Examples of test
results include comparisons of good and bad units and feature standard cone
type loudspeakers and compression drivers showing varying degrees of
conformity. In the final analysis, loudspeakers are tested for polarity,
frequency response and different types of distortion.

Modulation Distortion in Loudspeakers 2374573 bytes (CD aes3)
Author(s): Klipsch, Paul W.
Publication: Volume 17 Number 2 pp. 194, 196, 198, 200, 202, 204, 206; April
1969
Abstract: When comparing a loudspeaker with direct radiator bass system to
one with horn loaded bass, the subjective judgment is that the one with the
horn loaded bass is ·cleaner.· The difference in listening quality appears
to be due to modulation distortion. The mathematical analysis of modulation
distortion is reviewed and spectrum analyzer measurements are described
which have been correlated with listening tests. The spectrum analyses
corroborate the mathematical analysis and the listening tests offer a
subjective evaluation. It is concluded that frequency modulation in
loudspeakers accounts in large measure for the masking of ·inner voices.·
Reduction of diaphragm excursions at low frequencies reduces FM distortion.
Horn loading, properly applied, offers greatest reduction, while
simultaneously improving bass power output capability.

Why and How to Measure Distortion in Electroacoustic Transducers 1588948
bytes (CD aes16)
Author(s): Temme, Steve
Publication: Paper 11-028; Conference: The AES 11th International
Conference: AES Test & Measurement Conference; May 1992
Abstract: In the never-ending quest for better sound transmission,
reinforcement, and reproduction, the electronics has been extensively
analyzed for distortion. Distortion in electroacoustic transducers, while
typically several orders of magnitude greater, has often been neglected or
not even specified because it has been difficult to measure and interpret.
With a basic understanding of transducer limitations, some knowledge of
human hearing, and the application of different distortion test methods,
electroacoustic transducer distortion becomes easier to measure and assess.


T/60·How Do I Measure Thee, Let Me Count the Ways 4227391 bytes (CD aes11)
Author(s): D'Antonio, Peter; Eger, Don
Publication: Preprint 2368; Convention 81; November 1986
Abstract: A comparison of T60 values obtained in a certified NVLAP
reverberation chamber using conventional 1/3-octave decaying sound pressure
level (SPL method) measurements and time-delay spectrometry (TDS) is
presented. The TDS measurements were obtained from the least-squares slope
of a backward Schroeder integration of the total energy density versus time
for 16 fixed-bandwidth (1333 Hz) energy-time curves (ETC method) at
1/3-octave center frequencies and from a Peutz regression analysis of
1/3-octave averaged time-energy-frequency 3-D curves (TEF method). The SPL
method utilized a rotating microphone and a rotating vane diffuser. The ETC
and TEF methods were conducted with all combinations of rotating or
stationary microphone and vane diffuser, to evaluate their effect. The best
agreement between the SPL and ETC method was obtained using a spatial
averaging of stationary microphone measurements with the rotating vanes
stationary. The rotating vanes introduce the amplitude and frequency
modulation interference which caused discrepancies at frequencies of 1000 Hz
and higher, resulting in excessively large apparent T60s. On the other hand,
the best agreement between the SPL and TEF method was achieved using a
spatial average of stationary microphone measurements with the vanes
rotating. Stopping the vanes in the TEF method caused large discrepancies at
low frequencies of 500 Hz and below. This results from a decrease in the
number of excited modes which occurs when the Doppler effect of the rotating
vanes is removed. No advantage was realized infusing the moving microphone
technique in the TDS procedures. Since efficient broad-bandwidth wide-angle
fixed sound diffusers are now available, i the form of reflection phase
gratings, it should be possible to create a uniformly diffuse sound field
without rotating vanes, thus creating an environments where all T60
techniques could be performed accurately. A significant difference between
our integrated total energy density curves (TETC) and those of other
researchers using the integrated impulse response squared (IIR), is the
absence of spatially dependent fluctuations, even at 125 Hz, in our results.
A comparison between the IIR and IETC methods at 125 Hz, 250 Hz, and 500 Hz,
for the condition where the microphone and vanes were stationary, revealed
that the IIR curves were slightly more irregular but the overall backward
integration envelopes were similar. T60s obtained from the IIR for these
frequencies were approximately 4% lower than the IETC. Based on this
comparison and the smooth linearity of the decay curves, we conclude that
the sound field in the chamber was adequately diffuse.

The Modeling of the Nonlinear Response of an Electrodynamic Loudspeaker by
a Volterra Series Expansion 714668 bytes (CD aes11)
Author(s): Kaizer, A. J. M.
Publication: Preprint 2355; Convention 80; March 1986
Abstract: An electrodynamic loudspeaker is often assumed to be a linear
system. However, actual loudspeakers show small nonlinearities that give
rise to distortion components in its response. An overview of possible
nonlinearities in a practical electrodynamic loudspeaker is given in this
paper. The paper also presents a model of the nonlinear loudspeaker
behavior, which can be used to predict the low-frequency distortion of a
loudspeaker.

Modeling of the Nonlinear Response of an Electrodynamic Loudspeaker by a
Volterra Series Expansion 944788 bytes (CD aes4)
Author(s): Kaizer, A. J. M.
Publication: Volume 35 Number 6 pp. 421·433; June 1987
Abstract: The modeling of low-frequency nonlinear distortion in the response
of an electrodynamic loudspeaker by a Volterra series expansion is
described, an extension of ordinary linear network theory. A nonlinear
inversion circuit based on the Volterra series expansion, which is capable
of reducing the nonlinearities in the response, is described theoretically.
The harmonic and intermodulation distortion products of an actual
loudspeaker have been calculated using this tool. The distortion curves
predicted by the model and the measured distortion curves show a reasonable
agreement.

Amplitude and Frequency Modulation Distortions of a Loudspeaker 703036
bytes (CD aes4)
Author(s): Suzuki, Hideo; Shibata, Shigenori
Publication: Volume 32 Number 4 pp. 246-253; April 1984
Abstract: The measurement techniques and the causes of amplitude and
frequency modulation distortions are discussed using a two-way coaxial-type
loudspeaker system. The distortion due to amplitude modulation is caused by
the dependence of the radiation efficiency of the high-frequency driver on
the displacement of the diaphragm of the low-frequency driver. The
distortion due to frequency modulation seems to be produced when the
high-frequency sound has a nonzero particle velocity in the axis direction
at the surface of the low-frequency driver diaphragm. The symmetry of the
sidebands of the summed modulation distortion (intermodulation distortion)
indicates that the amplitude and frequency modulation distortions are 90°
out of phase with each other.

Amplitude and Frequency Modulation Distortion of a Loudspeaker 695994 bytes
(CD aes10)
Author(s): Suzuki, Hideo; Shibata, Shigenori
Publication: Preprint 1998; Convention 74; October 1983
Abstract: The measurement techniques and the causes of amplitude and
frequency modulation distortions are discussed using a two-way coaxial type
loudspeaker system. The distortion due to amplitude modulation is caused by
the dependence of the radiation efficiency of the high frequency driver on
the displacement of the diaphragm of the low frequency driver. The
distortion due to frequency modulation seems to be produced when the high
frequency sound has a non-zero particle velocity in the axis direction at
the surface of the low frequency driver's diaphragm. The symmetry of the
sidebands of the summed modulation distortion (intermodulation distortion)
indicates that the amplitude and frequency modulation distortions are 90 deg
out of phase with each other.

Analysis of the Nonrigid Behavior of a Loudspeaker Diaphram Using Modal
Analysis 794397 bytes (CD aes11)
Author(s): Struck, Christopher J.
Publication: Preprint 2779; Convention 86; March 1989
Abstract: The behavior of a loudspeaker diaphragm beyond the piston range of
operation has previously only been investigated using analytic techniques
such as the Finite Element Method. An experimental method, Modal Analysis,
is presented that allows a model to be developed from actual measurements.
Previous problems in the measurement technique are overcome by the use of a
non-contacting laser transducer. A step by step analysis of a typical driver
is shown. After developing the modal model, it is possible to simulate
structural modifications and to study the dynamic system response. Special
application software is used for the measurement, analysis, and simulation.


Loudspeaker Large-Signal Limitations 791820 bytes (CD aes10)
Author(s): Small, Richard H.
Publication: Preprint 2102; Convention 1r; September 1984
Abstract: Some of the nonlinear and time-varying characteristics of dynamic
loudspeakers are quite different from those of other audio components. These
must be understood for the successful design of loudspeakers intended for
high sound reproduction levels. Selected nonlinear mechanisms and related
distortions are discussed, together with techniques for measuring important
driver large-signal parameters.

Improving Loudspeaker Performance for Active Noise Control Applications
1128840 bytes (CD aes6)
Author(s): Lane, Steven A.; Clark, Robert L.
Publication: Volume 46 Number 6 pp. 508·519; June 1998
Abstract: Actuator performance plays an important part in active noise and
acoustic control. The loudspeakers that are normally used as actuators in
many active noise and acoustic control applications add significantly to the
dynamics of the control loop and can be detrimental to the controller's
performance. By compensating a loudspeaker with a technique similar to
motional feedback, the loudspeaker performance is enhanced for applications
such as control of acoustic enclosures. A method to compensate a loudspeaker
easily and reliably in order to approximate constant volume velocity
behavior over the piston-mode frequency range is presented and demonstrated.
This decouples the actuator from the system being controlled and reduces the
impact of the loudspeaker's dynamics over the control bandwidth.
Experimental results of the proposed method using a 5-in (127-mm)
loudspeaker are included.

A Comparison of Three Methods of Measuring the Volume Velocity of an
Acoustic Source 1187730 bytes (CD aes5)
Author(s): Anthony, D. K.; Elliott, S. J.
Publication: Volume 39 Number 5 pp. 355·366; May 1991
Abstract: Measurement of the volume velocity of an acoustic source allows
the acoustic transfer impedance seen by the source and its acoustic power
output to be determined. An investigation of three sources is described
whose volume velocity can be determined in different ways: using laser
velocimetry, using measurement of the internal source pressure, and using a
moving-coil loudspeaker as an output transducer (Salavaís method). Practical
implementation of each method is discussed. Using laser velocimetry as a
reference measurement, the accuracy of the other two sources is determined.
The total harmonic distortion at the acoustic output is also measured.
Salavaís method is shown to be superior in both respects. Example
measurements of acoustic transfer impedance within a duct and in a
well-damped room demonstrate the use of such sources as measurement tools.
The former is shown to adhere well to theoretical predictions. Preliminary
experiments are also reported concerning the practical measurement of
acoustic power output, and the use of this measurement to maximize the
acoustic power absorption of the source when exposed to an external sound
field.

Investigation of the Nonrigid Behavior of a Loudspeaker Diaphragm Using
Modal Analysis 745135 bytes (CD aes5)
Author(s): Struck, Christopher J.
Publication: Volume 38 Number 9 pp. 667·675; September 1990
Abstract: The behavior of a loudspeaker diaphragm beyond the piston range of
operation is usually investigated using analytic techniques such as the
finite-element method. An experimental method, modal analysis, is presented,
which allows a model to be developed from actual measurements. Previous
problems in the measurement technique are overcome by the use of a
noncontacting laser transducer. A step by step analysis of a typical driver
is shown. After the modal model has been developed it is possible to
simulate structural modifications and to study the dynamic system response.
Special application software is used for the measurement, analysis, and
simulation.


The Development of a Sandwich-Construction Loudspeaker System 1816043 bytes
(CD aes3)
Author(s): Barlow, D. A.
Publication: Volume 18 Number 3 pp. 269·281; June 1970
Abstract: The development of a complete loudspeaker system is described,
based on moving-coil loudspeakers with cones of sandwich construction of
immense rigidity. Piston action is obtained over a wide range. Other
features are described, such as the unique construction of the cabinet,
which reduces `boxy' coloration.

Fundamentals of Modern Audio Measurement 2940094 bytes (CD aes17)
Author(s): Cabot, Richard C.
Publication: Paper MOA-02; Conference: AES UK Conference: The Measure of
Audio (MOA); April 1997
Abstract: Fundamental concepts in testing audio equipment are reviewed,
beginning with an examination of the various equipment architectures in
common use. Several basic analog and digital audio measurements are
described. Trade-offs inherent in the various approaches, the technologies
used, and its limitations are discussed. Novel techniques employing
multitone signals for fast audio measurements are examined and applications
of sampling frequency correction technology to this and conventional fft
measurements are covered. Synchronous averaging of ffts and the subsequent
noise reduction are demonstrated. The need for simultaneity of digital and
analog generation is presented using converter measurements as an example.

Real-Time Virtual Acoustics for 5.1 356578 bytes (CD aes16)
Author(s): Flanagan, Patrick; Dickins, Glenn; Layton, Leonard
Publication: Paper 16-012; Conference: The AES 16th International
Conference: Spatial Sound Reproduction; April 1999
Abstract: A large body of knowledge exists for 3-D acoustical simulation
over loudspeaker arrays. These techniques can be used for generating
surround material for the 5.1 loudspeaker format. Using such tools, the
mixing process is replaced by the concept of creating virtual acoustical
simulations for which the 5.1 loudspeaker array is the target reproduction
array.
Comparison of Nonlinear Distortion Measurement Methods 1498614 bytes (CD
aes16)
Author(s): Cabot, Richard C.
Publication: Paper 11-007; Conference: The AES 11th International
Conference: AES Test & Measurement Conference; May 1992
Abstract: Several techniques are currently in use for measuring distortion
of audio equipment. These include THD, SMPTE intermodulation, difference
frequence intermodulation, and DIM (sinewave-squarewave combination). A new
technique is proposed which uses a relatively large number of sinewaves to
effect complex intermodulation products across the entire audio band. This
paper compares the various methods, both theoretically and practically.
Examples of measurements on several test circuits are presented to
illustrate the results.


Subjectively Perceived Sound Quality in Audio Systems as a Function of
Distribution and Number of Loudspeakers Used in Playback 1118449 bytes (CD
aes15)
Author(s): Kristoffersen, Rune; Kleiner, Mendel; Västfjäll, Daniel
Publication: Preprint 4876; Convention 106; May 1999
Abstract: Many home stereo systems are currently being upgraded to some form
of surround sound systems in order to obtain a better listening experience.
It is obvious that the sound quality obtained in the use of such systems
depends on the quality of the speakers as well as the properties of the
room. In this paper results are presented from a pilot study on the
subjective preference of non-linear distortion versus playback mode of
conventional stereo recordings. An auralization approach to the evaluation
of distortion characteristics of loudspeakers has been used for the first
time. Sound files have been created which were subject to three different
distortion generating non-linearities. The resulting sound files were then
convolved by the proper impulse responses of a simulated anechoic room and a
simulated living room using three different loudspeaker configurations. The
resulting binaural signals were played back via low distortion electrostatic
headphones in listening tests in order to investigate the relationship
between distortion and spatial distribution of sound. Results indicate that
some non-linear distortion is preferred and that surround sound allows less
stringent distortion requirements for the loudspeakers than mono or stereo.

Distortion Mechanisms of Distributed-Mode Loudspeakers (Compared with
Direct Pistonic Radiators; Modeling, Analysis, and Measurement) 811412 bytes
(CD aes14)
Author(s): Colloms, Martin; Gontcharov, Vladimir; Panzer, Joerg; Taylor,
Valerie
Publication: Preprint 4757; Convention 104; May 1998
Abstract: Acoustic radiation from a Distributed Mode Loudspeaker (DML)
results from low amplitude bending waves. Compared with the motor system of
a pistonic driver, the DML exciter is of subtly different design and
equivalent circuit with a different relationship to the radiating diaphragm.
In this paper, loudspeaker distortions are reviewed, the equivalent circuits
modeled and compared with the DML case, and the results for comparative
measurements are presented.

Sound Reproduction Applications with Wave-Field Synthesis 1232332 bytes (CD
aes14)
Author(s): Boone, Marinus M.; Verheijen, Edwin N. G.
Publication: Preprint 4689; Convention 104; May 1998
Abstract: Wave field synthesis (WFS) enables the reproduction of sound
fields in a principally much better way than other (multichannel)
reproduction systems do. Because of the spatial properties of the reproduced
sound field, a so-called volume solution is obtained. Emphasis is given to
practically optimized recording and reproduction techniques and
compatibility, forming the basis for applications that can benefit from the
spatial quality of WFS.

Fundamentals of Modern Audio Measurement 3367120 bytes (CD aes14)
Author(s): Cabot, Richard C.
Publication: Preprint 4604; Convention 103; September 1997
Abstract: Fundamental concepts in testing audio equipment are reviewed,
beginning with an examination of the various equipment architectures in
common use. Several basic analog and digital audio measurements are
described. Tradeoffs inherent in the various approaches, the techniques
used, and its limitations are discussed. Novel techniques employing
multitone signals for fast audio measurements are examined and applications
of sampling frequency correction technology to this and convention fat
measurements are covered. Synchronous averaging of fits and the ;subsequent
noise reduction are demonstrated. The need for simultaneity of digital and
analog generation is presented using converter measurements as an example.


Aspects of MLS Measuring Systems 1083800 bytes (CD aes12)
Author(s): Vanderkooy, John
Publication: Preprint 3398; Convention 93; October 1992
Abstract: A maximum-length sequence (MLS) has mathematical properties that
make it very useful as an excitation signal for measurement in audio and
acoustics. This paper explores the pathology of MLS systems when there is
distortion of various kinds. The resulting artefacts can falsify a
reverberation plot, reduce the distortion immunity of the measurement
system, and give rise to spurious reflections in the impulse response, to
name a few negative aspects. On the other hand, MLS systems can also allow
the determination of the total distortion of an electroacoustic system when
excited by a signal of any desired spectrum, and sensitive tests for
determining the presence of distortion are possible due to the time-domain
separation of linear and nonlinear components.

Constant Component of the Loudspeaker Diaphragm Displacement Caused by
Non-Linearities 375516 bytes (CD aes11)
Author(s): Dobrucki, A.
Publication: Preprint 2577; Convention 84; March 1988
Abstract: The independent of time component of displacement appears, apart
from increase of even harmonics, if the most significant nonlinear
characteristics of loudspeaker i.e. nonlinear stiffness of suspensions and
nonhomogeneous magnetic field in the gap are nonsymmetrical in relation to
the rest position of the diaphragm and voice coil. In some conditions, the
value of this displacement can be so large, that the normal action of the
loudspeaker will be disturbed. In the paper, the phenomenon is studied both
theoretically and experimentally. It is proven that dependence of the
constant component of frequency of modulation is different in the case of
nonsymmetrical stiffness of suspension than in the case of unhomogenous
magnetic field in the gap. This fact can be used to identify the reason for
the appearance of constant component, its minimization and decreasing of
harmonic content.

A Standard Monitor Loudspeaker Used as a Reference for Digital Audio
Productions in Studios with Different Acoustic Properties 4111561 bytes (CD
aes18)
Author(s): Goldstein, Samuel H.
Publication: Preprint 1968; Convention 73; March 1983
Abstract: Loudspeakers having an ideal frequency response in an anechoic
room sound different in monitor rooms having other acoustic properties. In
these rooms, which are not ideal from the acoustical point of view, the
sound is reflected to the listener with frequency responses differing so
much from one another that the first (nonreflecting) sound component is
received with an ideal response, whereas the delayed ground-reflected sound
features a bass boost, the sound reflected by the ceiling makes an extremely
present impression and in the lateral reflections the lower midrange is
missing. These great deviations of the polar pattern are due to the
frequency differences. This paper describes an active monitor loudspeaker
system having a practically uniform polar response over the total listening
range.

Phase Distortion and Phase Equalization in Audio Signal Processing·A
Tutorial Review 3113054 bytes (CD aes10)
Author(s): Preis, Douglas
Publication: Preprint 1849; Convention 70; October 1981
Abstract: Various definitions and measures of phase distortion are reviewed
beginning with first principles. Numerous representative examples are
included indicating quantitative amounts of phase distortion produced by
microphones, loudspeakers, coaxial cables, anti-alias filters and magnetic
recording. The effects of phase distortion on time-domain performance are
discussed. A frequency-dependent tolerance on group delay distortion is
developed based on seven different perceptual studies and compared with some
representative measurements. New and complementary experiments are proposed
to assess further the perceptual significance of phase distortion in music
reproduction. Methods of phase equalization and phase equalizer design are
presented. A new time-frequency display, showing both the location of a
signal in time and its frequency spread, is introduced which provides a more
unified view of time-domain and frequency-domain interrelationships.

A Revolutionary 3-D Interferometric Vibrational Mode Display 1329271 bytes
(CD aes9)
Author(s): Bank, G.; Hathaway, G. T.
Publication: Preprint 1658; Convention 66; May 1980
Abstract: When the beam from a laser vibration interferometer is optically
raster scanned over a vibrating surface a phase sensitive detector provides
velocity information at any phase of the motion. This data is digitally
processed and hard copy print gives a 3-D isometric view of the complete
vibrating surfaces of the test object frozen in time.

A Comparison of Nonlinear Distortion Measurement Methods 2000998 bytes (CD
aes9)
Author(s): Cabot, Richard C.
Publication: Preprint 1638; Convention 66; May 1980
Abstract: Several techniques are currently in use for measuring distortion
of audio equipment. These include THD, IM-difference frequency, sine-square,
random noise, and recently a three-tone intermodulation distortion test has
been proposed. This paper compares the various methods, both theoretically
and practically. The effects of changing the test frequencies used in each
test on its sensitivity and practicality are discussed. It is found that
this yields a significant improvement in sensitivity to many forms of
distortion.


Time Distortion in Loudspeakers 553257 bytes (CD aes9)
Author(s): Lian, R.
Publication: Preprint 1207; Convention 56; March 1977
Abstract: From the fundamental pressure/time functions, this paper describes
the different types of distortion appearing in loudspeakers. Special
attention is paid to time and pitch distortion. Different mechanical
solutions in loudspeaker driver design, and their influence on
magnitude/time distortion are discussed. Some preliminary conclusions are
drawn, though the paper proposes more questions than answers.

Swept Electroacoustic Measurements of Harmonic Distortion,
Difference-Frequency and Intermodulation Distortion 1271330 bytes (CD aes8)
Author(s): Thomsen, Carsten; Møller, Henning
Publication: Preprint 1068; Convention 52; October 1975
Abstract: In music, many frequencies occur simultaneously, therefore
distortion tests which are relevant to music must be carried out using more
than one frequency. A system is introduced for automatic swept measurement
of harmonic distortion, difference frequency and intermodulation distortion
in the range 2 Hz-200 kHz. The relationship of high-frequency (up to 200
kHz) IM and difference-frequency distortion to transient intermodulation
(TIM) is explored. The system consists of a sweeping two-tone generator and
a heterodyne analyzer phase-locked to the selected distortion components up
to the fifth order. Typical dynamic range permits measurements down to 0.01
% in the harmonic and difference-frequency modes, and to 0.001% in the IM
mode.

Intermodulation Distortion Listening Tests 359592 bytes (CD aes8)
Author(s): Fryer, P. A.
Publication: Preprint L-10; Convention 50; March 1975
Abstract: It is fairly simple to measure the amount of intermodulation
distortion produced by loudspeakers, but it is more difficult to find out
how much of this kind of distortion is found objectionable (or just
detectable) when masked by music. It is made more difficult by the fact that
this has to be done in the absence of other kinds of distortion such as
harmonic and transient intermodulation distortion. In order to measure the
effects of intermodulation distortion, a 'black box' was built which was
capable of generating a known and controllable percentage of pure
intermodulation distortion, and then listening tests were held at different
sound pressure levels with different kinds of music with several speakers
and listeners. The results show that intermodulation distortion is masked to
a large extent by music but it can be easily detected when pure tones are
used.

Threshold of Phase Detection by Hearing 1042299 bytes (CD aes8)
Author(s): Hansen, Villy; Madsen, Erik Rørbaek
Publication: Preprint C-1; Convention 44; March 1973
Abstract: For years, the ability to detect phase distortion in musical
signals has been a much debated question. Research has been carried out for
the purpose of finding a suitable complex signal whose different frequency
components could be changed in phase without altering the amplitude spectrum
of the signal. Subjective listening tests have been made on a number of
listeners in order to find the threshold of phase detection. the test was
carried out with high-fidelity headphones and high-fidelity loudspeakers in
a semi-reverberant room. It is proven experimentally that phase detection
increases in a reverberant room and when using loudspeakers having poor
transfer characteristics. It is demonstrated that the ear prefers the
frequency content in the negative pressure transient fronts. This
demonstrates the importance of absolute phase, for which reason there should
be standardization of phase conditions from sound source to sound
reproducer.

Modulation Distortion in Loudspeakers 593264 bytes (CD aes7)
Author(s): Klipsch, Paul W.
Publication: Preprint 562; Convention 34; April 1968
Abstract: When comparing 2 loudspeakers, one with direct radiator bass
system and the other with horn loaded bass, a subjective judgment was that
the one with the horn loaded bass is ·cleaner.· Both speakers were by the
same manufacturer. Various tests were applied and by process of elimination
it appears the difference in listening quality is due to frequency
modulation distortion. Beers and Belar analyzed this form of distortion in
1943, but since that time the effect has been almost ignored. Now, with
amplifiers and source material reaching new lows in distortion, differences
between good loudspeakers begin to appear significant. The mathematical
analysis has been reviewed, and measurements have been made using a spectrum
analyzer. These have been correlated with listening tests by preparing tapes
of oscillator tones and music with and without a low frequency source to
produce frequency modulation distortion. The spectrum analyses corroborate
the mathematical analysis and the listening tests offer a subjective
evaluation. The conclusion is that frequency modulation in loudspeakers
accounts in large measure for the masking of ·inner voices.· As Beers and
Belar put it, ·The sound is just not clean.· Reduction of diaphragm
excursions at lower frequencies reduces FM distortion. Horn loading,
properly applied, offers the greatest reduction, while simultaneously
improving bass power output capability. Tentatively it is wondered if FM
distortion in loudspeakers may be the last frontier in loudspeaker
improvement.

Distortion Measurements of High-Frequency Loudspeakers 2872873 bytes (CD
aes7)
Author(s): Kantrowitz, Philip
Publication: Preprint 218; Convention 13; October 1961
Abstract: The relative importance of linearity and distortion in
high-frequency loudspeakers has been investigated. Hemispherical direct
radiators, conical direct radiators, a ribbon horn, dynamic horns, a
single-ended and a push-pull electrostatic speaker were evaluated for
frequency response, non-linear distortion and directionality. Quadratic and
cubic non-linear distortion terms are present in high-frequency
loudspeakers. The maximum cubic CCIF non-linear distortion in horns is
greater than that found for the direct radiator and push-pull electrostatic
types. Smoothness of response, directional characteristics and extent of
frequency range are generally more significant than distortion in the
classification of the ·listenability· of the high-frequency loudspeaker.
Subjective listening tests, however, indicate that total CCIF non-linear
distortion above approximately 3% is objectionable. In a complete speaker
system, the capabilities of a superior high-frequency loudspeaker may be
severely limited or altered due to the selection of an improper cross-over
netowrk or the use of inferior middle and low range speaker units.
Introductory Remarks to the Session on Acoustics in Oceanographic Research,
and Sound - The Test Probe to Sense the Ocean 590514 bytes

Fundamentals of Modern Audio Measurement 10045860 bytes (CD aes6)
Author(s): Cabot, Richard C.
Publication: Volume 47 Number 9 pp. 738·744, 746-762; September 1999
Abstract: Fundamental concepts in testing audio equipment are reviewed,
beginning with an examination of the various equipment architectures in
common use. Several basic analog and digital audio measurements are
described. Tradeoffs inherent in the various approaches, the technologies
used, and their limitations are discussed. Novel techniques employing
multitone signals for fast audio measurements are examined and applications
of sampling frequency correction technology to this and conventional FFT
measurements are covered. Synchronous averaging of FFTs and the subsequent
noise reduction are demonstrated. The need for simultaneity of digital and
analog generation is presented using converter measurements as an example.

Fifty Years of Loudspeaker Developments as Viewed Through the Perspective
of the Audio Engineering Society 3982910 bytes (CD aes6)
Author(s): Gander, Mark R.
Publication: Volume 46 Number 1/2 pp. 43-58; January 1998
Abstract: An exhaustive review of over 450 AES Journal loudspeaker papers
and other select references is presented and categorized by subject area.
The names and affiliations of the authors are included. Perspective is given
on the technical significance, degree of influence, and historical context
of the contributions and contributors. Except where otherwise noted, all
references are from the Journal of the Audio Engineering Society and, where
applicable, the volumes of the AES Loudspeakers anthology.

Aspects of MLS Measuring Systems 1225899 bytes (CD aes5)
Author(s): Vanderkooy, John
Publication: Volume 42 Number 4 pp. 219·231; April 1994
Abstract: A maximum-length sequence (MLS) has mathematical properties that
makeit very useful as an excitation signal for measurement in audio and
acoustics. The pathology of MLS systems when there is distortion of various
kinds is explored. The resulting artifacts can falsify a reverberation plot,
reduce the distortion immunity of the measurement system, and give rise to
spurious reflections in the impulse response, to name a few negative
aspects. On the other hand, MLS systems can also allow the determination of
the total distortion of an electroacoustic system when excited by a signal
of any desired spectrum, and sensitive tests for determining the presence of
distortion are possible due to the time-domain separation of linear and
nonlinear components.


Direct Low-Frequency Driver Synthesis from System Specifications 1144589
bytes (CD aes4)
Author(s): Keele, Jr., D. B.
Publication: Volume 30 Number 11 pp. 800·814; November 1982
Abstract: The usual procedure for direct-radiator low-frequency loudspeaker
system design leads to the calculation of the driver's fundamental
electromechanical parameters by an intermediate specification of the
Thiele-Small parameters. A reformulation of the synthesis procedure to
eliminate the intermediate Thiele-Small calculation leads to a set of
equations that yield the driver's electromechanical parameters directly from
the system specifications. These equations reveal some moderately surprising
relationships when the different system types (closed box, fourth-order
vented box, and sixth-order vented box) are compared. For example, for a
specified low-frequency cutoff f(3), midband efficiency, and driver size the
fourth-order vented-box driver is found to be roughly three times more
expensive (judged on the amount of magnet energy required) than the
closed-box driver. Conversely for a given f(3), enclosure volume V(B),
maximum diaphragm excursion X(max), and acoustic power output P(AR) the
fourth-order vented-box driver is some five times cheaper than the
closed-box driver. It is also found that for direct-radiator systems in
general, specified f(3), V(B), X(max), and P(AR) lead to the total moving
mass M(MS) depending inversely on the sixth power of the cutoff frequency,
that is, a one-third-octave reduction in f(3) results in a fourfold increase
in mass. Furthermore, the same conditions reveal that the sixth-order
vented-box driver moving mass is some 42 times lighter than that of the
closed-box driver, providing the same midband acoustic output and f(3). If
cone area and efficiency are held constant, the direct-radiator system
driver actually gets less expensive as the low-frequency limit is extended.

Phase Distortion and Phase Equalization in Audio Signal Processing·A
Tutorial Review 2705909 bytes (CD aes4)
Author(s): Preis, D.
Publication: Volume 30 Number 11 pp. 774·794; November 1982
Abstract: Various definitions and measurements of phase distortion are
reviewed beginning with first principles. Numerous representative examples
are included, indicating quantitative amounts of phase distortion produced
by microphones, loudspeakers, coaxial cables, antialias filters, and
magnetic recording. The effects of phase distortion on time-domain
performance are discussed. A frequency-dependent tolerance on group-delay
distortion is developed based on seven different perceptual studies and
compared with some representative measurements. New and complementary
experiments are proposed to assess further the perceptual significance of
phase distortion in music reproduction. Methods of phase equalization and
phase equalizer design are presented. A new time-frequency display, showing
both the location of a signal in time and its frequency spread, is
introduced, which provides a more unified view of time-domain and
frequency-domain interrelationships.


Modulation Distortion in Loudspeakers: Part 3 187326 bytes (CD aes3)
Author(s): Klipsch, Paul W.
Publication: Volume 20 Number 10 pp. 827·828; December 1972
Abstract: Distortion in loudspeakers is shown to be nearly proportional to
power output. Typically a plot of log distortion versus dB output shows a
1:1 relation. In one sample ooudspeaker the slope of the distortion versus
output curve was in excess of 45 degrees. Comparison is shown between a
direct radiator of 20-cm (8-in) diameter, one of 30-cm (12-in) diameter, and
a high-efficiencØ horn of 0.45 m/3 (16 ft/3). At 95-dB sound pressure level
output measured at 61 cm (2 ft) the 12-cm cone showed 18% (·15 dB ref 100%),
the 30-cm cone showed 6% (·25 dB ref 100%), and the horn showed 0.8% (·42 dB
ref 100%). Each curve of distortion versus output shows a slope of at least
45 degrees.

Comments on "Modulation Distortion in Loudspeakers" and Author's Reply
259555 bytes (CD aes3)
Author(s): Cole, Sr., T. S.; Klipsch, Paul
Publication: Volume 17 Number 4 pp. 448-449; August 1969
Abstract: Not available.

Acoustical Measurements by Time Delay Spectrometry 2331867 bytes (CD aes2)
Author(s): Heyser, Richard C.
Publication: Volume 15 Number 4 pp. 370·382; October 1967
Abstract: A new acoustical measurement technique has been developed that
provides a solution for the conflicting requirements of anechoic spectral
measurements in the presence of a reverberant environment. This technique,
called time delay spectrometry, recognizes that a system-forcing function
linearly relating frequency with time provides spatial discrimination of
signals of variable path length when perceived by a frequency-tracking
spectrum analyzer.

Epilogue on Measurements 222950 bytes (CD aes2)
Author(s): Cooper, Duane H.
Publication: Volume 12 Number 4 pp. 344, 346; October 1964
Abstract: Not available.
Distortion of High-Frequency Loudspeakers 770716 bytes (CD aes2)
Author(s): Kantrowitz, Philip
Publication: Volume 10 Number 4 pp. 310·317; October 1962
Abstract: The relative importance of linearity and distortion in
high-frequency loudspeakers was investigated. Hemispherical direct
radiators, conical direct radiators, a ribbon horn, dynamic horns, a
single-ended and a push-pull electrostatic speaker were evaluated for
frequency response, nonlinear distortion and directionality. Quadratic and
cubic non-linear distortion terms were found to be present in high-frequency
loudspeakers. The maximum cubic CCIF nonlinear distortion in horns was
greater than that found for the direct radiator and push-pull electrostatic
types. Smoothness of response, directional characteristics and extent of
frequency range were generally more significant than distortion in the
classification of the ·listenability· of the high-frequency loudspeaker.
Subjective listening tests, however, indicated that total CCIF non-linear
distortion above approximately 3% is objectionable. It was found that in a
complete speaker system, the capabilities of a superior high-frequency
loudspeaker may be severely limited or altered due to the selection of an
improper cross-over network or the use of inferior middle and low range
speaker units.

enjoy! ;-)

[Arny Krueger]

"Chris Hornbeck" > wrote in message

> On Thu, 12 Aug 2004 07:16:34 -0400, "Arny Krueger" >
> wrote:
>
>>> I see two flaws here. First is that the FM exists *at the
>>> diaphragm* and is independent of media.
>>
>> The FM exists at the receiver or listener. If the speaker and the
>> listener have no relative velocity, no Doppler.
>>
>> People who ride on trains don't hear the whistle of their train as
>> being Doppler-shifted.
>
> You raise a very interesting point and I'm not smart enough to
> figure it out myself.
>
> Suppose the listener were mounted on a (very strong) diaphragm
> driven by the same signal, EQ'ed and time-delayed, as the source
> diaphragm, in order to cancel out their relative movement.
>
> Would the listener still hear the FM sidebands?

No relative motion, no Doppler distortion.

[Arny Krueger]

"Chris Hornbeck" > wrote in message

> On Thu, 12 Aug 2004 07:16:34 -0400, "Arny Krueger" >
> wrote:
>
>>> I see two flaws here. First is that the FM exists *at the
>>> diaphragm* and is independent of media.
>>
>> The FM exists at the receiver or listener. If the speaker and the
>> listener have no relative velocity, no Doppler.
>>
>> People who ride on trains don't hear the whistle of their train as
>> being Doppler-shifted.
>
> You raise a very interesting point and I'm not smart enough to
> figure it out myself.
>
> Suppose the listener were mounted on a (very strong) diaphragm
> driven by the same signal, EQ'ed and time-delayed, as the source
> diaphragm, in order to cancel out their relative movement.
>
> Would the listener still hear the FM sidebands?

No relative motion, no Doppler distortion.

[Arny Krueger]

"Phil Allison" > wrote in message

>
> ** Dunno what you are on about - Doppler is a linear phenomenon,
> not some kind of distortion product. It is simply the result of a
> moving source creating longer or shorter wavelengths in the air than
> it would if stationery.

Oh, you are so completely and totally wrong! This is bad, even for you.
You've got just about every point totally wrong. But you know what, I'm
quite sure that it takes a smart, fairly-well-educated person to screw up
like this. You know your stuff, just not perfectly! ;-)

Doppler is nonlinear distortion. It creates signals at additional
frequencies that were not part of the original signal.

<Now folks, if I were Phil, I'd say something inflammatory here about Phil
not knowing the definition of nonlinear distortion. I'm quite sure he knows
it, but guess what, he's not perfect! Nobody is as perfect as Phil thinks he
is, not even Phil ;-)>

Doppler is the result of relatively motion between the transmitter and
receiver, causing shorter or longer wavelengths to be received by the
receiver.

<Now folks, if I were Phil, I'd say something inflammatory here about Phil
not knowing the definition of Doppler distortion. I'm quite sure he knows
it, but guess what, he's not perfect!>

> Shame that dumb spectrum analysers cannot tell the difference
> between minor amounts of AM and very narrow FM with a high index
> figure - that fact has cast doubt over practically all the test
> results that are claimed to show Doppler shift in the sound coming
> from woofers.

It's not the analyzer's fault, its the fault of the people setting up the
analyzer and interpreting the results.

Phil, guns don't kill people, people kill people. Take the guns away, you
save a fair number of lives because it's harder to kill someone without a
gun, but there would still be lots of murder.

[Arny Krueger]

"Phil Allison" > wrote in message

>
> ** Dunno what you are on about - Doppler is a linear phenomenon,
> not some kind of distortion product. It is simply the result of a
> moving source creating longer or shorter wavelengths in the air than
> it would if stationery.

Oh, you are so completely and totally wrong! This is bad, even for you.
You've got just about every point totally wrong. But you know what, I'm
quite sure that it takes a smart, fairly-well-educated person to screw up
like this. You know your stuff, just not perfectly! ;-)

Doppler is nonlinear distortion. It creates signals at additional
frequencies that were not part of the original signal.

<Now folks, if I were Phil, I'd say something inflammatory here about Phil
not knowing the definition of nonlinear distortion. I'm quite sure he knows
it, but guess what, he's not perfect! Nobody is as perfect as Phil thinks he
is, not even Phil ;-)>

Doppler is the result of relatively motion between the transmitter and
receiver, causing shorter or longer wavelengths to be received by the
receiver.

<Now folks, if I were Phil, I'd say something inflammatory here about Phil
not knowing the definition of Doppler distortion. I'm quite sure he knows
it, but guess what, he's not perfect!>

> Shame that dumb spectrum analysers cannot tell the difference
> between minor amounts of AM and very narrow FM with a high index
> figure - that fact has cast doubt over practically all the test
> results that are claimed to show Doppler shift in the sound coming
> from woofers.

It's not the analyzer's fault, its the fault of the people setting up the
analyzer and interpreting the results.

Phil, guns don't kill people, people kill people. Take the guns away, you
save a fair number of lives because it's harder to kill someone without a
gun, but there would still be lots of murder.

[William Sommerwerck]

>> In the case of lightning, isn't it the thermal expansion
>> of the air that causes the sound of thunder?

> Yes, but it isn't what makes an ion speaker speak. :-)

Yes, it is. Ask Dr. Hill.

[William Sommerwerck]

>> In the case of lightning, isn't it the thermal expansion
>> of the air that causes the sound of thunder?

> Yes, but it isn't what makes an ion speaker speak. :-)

Yes, it is. Ask Dr. Hill.

[William Sommerwerck]

> William Sommerwerck wrote:

>>>> Yes. That's how plasma speakers work. (I heard this
>>>> straight from the mouth of Dr. Allen Hill.)

>>> I don't think so. The plasma is an ionized state of air
>>> which means it is charged and will move in response
>>> to an applied electric field.

>> You might choose so, but I'm inclined to believe the good Dr. He did a huge
>> amount of both practical and theoretical research on ionic speakers -- he
gave
>> us a slide show -- before developing the Plasmatronics speaker.

> Appeals to authority can be problematic. Check the theory
> for yourself. No way to transfer heat into the air fast
> enough to get any kind of bandwidth.

I, too, dislike appealing to authority. But I've met Dr. Hill, talked with him
at length, and he's no dummy. Ionic speakers do NOT work by "pushing" the air in
front of them. The sound is a PV = nRT effect, where changes in temperature
produce pressure changes.

Dr. Hill also developed what he called a "toaster woofer," nichrome wire strung
around a heat-resistant form. He claimed that the reason toasters hum could be
used to reproduce sound. I never saw a demo, though.

[William Sommerwerck]

> William Sommerwerck wrote:

>>>> Yes. That's how plasma speakers work. (I heard this
>>>> straight from the mouth of Dr. Allen Hill.)

>>> I don't think so. The plasma is an ionized state of air
>>> which means it is charged and will move in response
>>> to an applied electric field.

>> You might choose so, but I'm inclined to believe the good Dr. He did a huge
>> amount of both practical and theoretical research on ionic speakers -- he
gave
>> us a slide show -- before developing the Plasmatronics speaker.

> Appeals to authority can be problematic. Check the theory
> for yourself. No way to transfer heat into the air fast
> enough to get any kind of bandwidth.

I, too, dislike appealing to authority. But I've met Dr. Hill, talked with him
at length, and he's no dummy. Ionic speakers do NOT work by "pushing" the air in
front of them. The sound is a PV = nRT effect, where changes in temperature
produce pressure changes.

Dr. Hill also developed what he called a "toaster woofer," nichrome wire strung
around a heat-resistant form. He claimed that the reason toasters hum could be
used to reproduce sound. I never saw a demo, though.

[William Sommerwerck]

> Now I am interested in the **mechanism** that allows that volume
> [of?] air moving in unison with a woofer cone with a high frequency
> pressure wave travelling through it to *transfer* that high frequency
> wave to the still air further away.

There is no mechanism. The energy of the HF wave is self-propagating.

[William Sommerwerck]

> Now I am interested in the **mechanism** that allows that volume
> [of?] air moving in unison with a woofer cone with a high frequency
> pressure wave travelling through it to *transfer* that high frequency
> wave to the still air further away.

There is no mechanism. The energy of the HF wave is self-propagating.

[Phil Allison]

"William Sommerwerck"

> > Now I am interested in the **mechanism** that allows that volume
> > [of?] air moving in unison with a woofer cone with a high frequency
> > pressure wave travelling through it to *transfer* that high frequency
> > wave to the still air further away.
>
> There is no mechanism.


** There always is.


> The energy of the HF wave is self-propagating.


** So dogs bark and cats meow.

You have missed the point entirely.




............. Phil

[Phil Allison]

"William Sommerwerck"

> > Now I am interested in the **mechanism** that allows that volume
> > [of?] air moving in unison with a woofer cone with a high frequency
> > pressure wave travelling through it to *transfer* that high frequency
> > wave to the still air further away.
>
> There is no mechanism.


** There always is.


> The energy of the HF wave is self-propagating.


** So dogs bark and cats meow.

You have missed the point entirely.




............. Phil

[Carey Carlan]

(Noel Bachelor) wrote in
:

> If they are real sounds, and were captured by a single microphone,
> then a similar doppler shifting would be encoded by the microphone, so
> the speaker would simply be decoding that, and effectively restoring
> the HF tone to it's original timing. Of course the mic would
> typically have less excursion than the speaker, but if frequency
> response was flat for both, everything should be in the same balance.

Your argument assumes that the microphone diaphragm moves the same extent
during recording as the speaker does during playback.

[Carey Carlan]

(Noel Bachelor) wrote in
:

> If they are real sounds, and were captured by a single microphone,
> then a similar doppler shifting would be encoded by the microphone, so
> the speaker would simply be decoding that, and effectively restoring
> the HF tone to it's original timing. Of course the mic would
> typically have less excursion than the speaker, but if frequency
> response was flat for both, everything should be in the same balance.

Your argument assumes that the microphone diaphragm moves the same extent
during recording as the speaker does during playback.

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
>
>
> >>Thanks, I'll give it a study. I've already found a wrong
> >>working assumption, that the sound pressure created by a
> >>driver is proportional to its acceleration rather than its
> >>velocity and don't know yet how far that pervades the analysis.
> >>

> >
> > ** That comment is quite accurate - cone acceleration is the parameter
> > that matches radiated SPL from a moving cone.
> > Consider that the force acting on a voice coil is proportional to the
> > applied current and the moving mass is fixed. From F = mA we have the
result
> > that cone acceleration is proportional to applied current at any
instant.
>
> Ok. The false assumption is that the pressure wave created
> by a piston is proportional to its acceleration. It isn't;
> it's proprotional to the piston velocity.


** You have evidence ????

>
> > ** Dunno what you are on about - Doppler is a linear phenomenon, not
some
> > kind of distortion product. It is simply the result of a moving source
> > creating longer or shorter wavelengths in the air than it would if
> > stationery.
>
>
> Didn't I explain what a linear system is in a prior post?


** No interest to me or anyone else what YOU decide the laws of nature
are.


> Nothing that produces "frequencies" that aren't in what's
> driving it is linear.


** Pure gobbledegook.

Try defining your terms in a consistent and familiar manner.

I might just help you to make sense.



........... Phil

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
>
>
> >>Thanks, I'll give it a study. I've already found a wrong
> >>working assumption, that the sound pressure created by a
> >>driver is proportional to its acceleration rather than its
> >>velocity and don't know yet how far that pervades the analysis.
> >>

> >
> > ** That comment is quite accurate - cone acceleration is the parameter
> > that matches radiated SPL from a moving cone.
> > Consider that the force acting on a voice coil is proportional to the
> > applied current and the moving mass is fixed. From F = mA we have the
result
> > that cone acceleration is proportional to applied current at any
instant.
>
> Ok. The false assumption is that the pressure wave created
> by a piston is proportional to its acceleration. It isn't;
> it's proprotional to the piston velocity.


** You have evidence ????

>
> > ** Dunno what you are on about - Doppler is a linear phenomenon, not
some
> > kind of distortion product. It is simply the result of a moving source
> > creating longer or shorter wavelengths in the air than it would if
> > stationery.
>
>
> Didn't I explain what a linear system is in a prior post?


** No interest to me or anyone else what YOU decide the laws of nature
are.


> Nothing that produces "frequencies" that aren't in what's
> driving it is linear.


** Pure gobbledegook.

Try defining your terms in a consistent and familiar manner.

I might just help you to make sense.



........... Phil

[Scott Dorsey]

In article >,
William Sommerwerck > wrote:
>>> In the case of lightning, isn't it the thermal expansion
>>> of the air that causes the sound of thunder?
>
>> Yes, but it isn't what makes an ion speaker speak. :-)
>
>Yes, it is. Ask Dr. Hill.

Depends on the speaker. I think the Hill devices had a sheet of plasma
in a magnetic field, and by shifting the magnetic field you could move
the plasma forward and back and thereby move air with it. But I do recall
another device that relied on changing ionization.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

In article >,
William Sommerwerck > wrote:
>>> In the case of lightning, isn't it the thermal expansion
>>> of the air that causes the sound of thunder?
>
>> Yes, but it isn't what makes an ion speaker speak. :-)
>
>Yes, it is. Ask Dr. Hill.

Depends on the speaker. I think the Hill devices had a sheet of plasma
in a magnetic field, and by shifting the magnetic field you could move
the plasma forward and back and thereby move air with it. But I do recall
another device that relied on changing ionization.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison]

"Arny Krueger"
> "Phil Allison"
>>
> > ** Dunno what you are on about - Doppler is a linear phenomenon,
> > not some kind of distortion product. It is simply the result of a
> > moving source creating longer or shorter wavelengths in the air than
> > it would if stationery.
>
> Oh, you are so completely and totally wrong!


** Go **** yourself - Arny.

You have nothing even faintly sane to say and you are acting like a maniac.


> Doppler is nonlinear distortion. It creates signals at additional
> frequencies that were not part of the original signal.


** The Doppler effect is however a linear phenomenon.

( snip idiotic, gratuitous insults form a raving maniac )


> Doppler is the result of relatively motion between the transmitter and
> receiver, causing shorter or longer wavelengths to be received by the
> receiver.


( snip idiotic, gratuitous insults form a raving maniac )


>
> > Shame that dumb spectrum analysers cannot tell the difference
> > between minor amounts of AM and very narrow FM with a high index
> > figure - that fact has cast doubt over practically all the test
> > results that are claimed to show Doppler shift in the sound coming
> > from woofers.
>
> It's not the analyzer's fault, its the fault of the people setting up the
> analyzer and interpreting the results.


** Ridiculous gobbledegook - Arny's fake analogy posted below makes my
point for me.


> Phil, guns don't kill people, people kill people. Take the guns away, you
> save a fair number of lives because it's harder to kill someone without a
> gun, but there would still be lots of murder.



** So Arny is now a looney gun freak as well as an all round, manic lunatic
these days.


Tell me Arny - who had the bad news from the medicos ???




............. Phil

[Phil Allison]

"Arny Krueger"
> "Phil Allison"
>>
> > ** Dunno what you are on about - Doppler is a linear phenomenon,
> > not some kind of distortion product. It is simply the result of a
> > moving source creating longer or shorter wavelengths in the air than
> > it would if stationery.
>
> Oh, you are so completely and totally wrong!


** Go **** yourself - Arny.

You have nothing even faintly sane to say and you are acting like a maniac.


> Doppler is nonlinear distortion. It creates signals at additional
> frequencies that were not part of the original signal.


** The Doppler effect is however a linear phenomenon.

( snip idiotic, gratuitous insults form a raving maniac )


> Doppler is the result of relatively motion between the transmitter and
> receiver, causing shorter or longer wavelengths to be received by the
> receiver.


( snip idiotic, gratuitous insults form a raving maniac )


>
> > Shame that dumb spectrum analysers cannot tell the difference
> > between minor amounts of AM and very narrow FM with a high index
> > figure - that fact has cast doubt over practically all the test
> > results that are claimed to show Doppler shift in the sound coming
> > from woofers.
>
> It's not the analyzer's fault, its the fault of the people setting up the
> analyzer and interpreting the results.


** Ridiculous gobbledegook - Arny's fake analogy posted below makes my
point for me.


> Phil, guns don't kill people, people kill people. Take the guns away, you
> save a fair number of lives because it's harder to kill someone without a
> gun, but there would still be lots of murder.



** So Arny is now a looney gun freak as well as an all round, manic lunatic
these days.


Tell me Arny - who had the bad news from the medicos ???




............. Phil

[Chris Hornbeck]

On Fri, 13 Aug 2004 01:56:22 -0700, Bob Cain
> wrote:

>Yeah, I'm hoping for citations that provide a complete
>theory for the effect from which the result of any driving
>point velocity or pressure can be predicted. There is no
>good reason why this doesn't exist except possibly for one.

I'm puzzled why you're unconvinced by an argument from
Terman, rotating vectors and such like. Doesn't the diaphragm
itself contain enough information (for a fixed listener?)

>Everything is really subjective to this point without the
>requisite separation of variables.

So, ignoring the side arguments of audibility and testing
procedures, is your quest located at the diaphragm-air
translation?

Thanks,

Chris Hornbeck

[Chris Hornbeck]

On Fri, 13 Aug 2004 01:56:22 -0700, Bob Cain
> wrote:

>Yeah, I'm hoping for citations that provide a complete
>theory for the effect from which the result of any driving
>point velocity or pressure can be predicted. There is no
>good reason why this doesn't exist except possibly for one.

I'm puzzled why you're unconvinced by an argument from
Terman, rotating vectors and such like. Doesn't the diaphragm
itself contain enough information (for a fixed listener?)

>Everything is really subjective to this point without the
>requisite separation of variables.

So, ignoring the side arguments of audibility and testing
procedures, is your quest located at the diaphragm-air
translation?

Thanks,

Chris Hornbeck

[Chris Hornbeck]

On Fri, 13 Aug 2004 08:13:08 -0400, "Arny Krueger" >
wrote:

>Doppler is nonlinear distortion. It creates signals at additional
>frequencies that were not part of the original signal.

>Doppler is the result of relatively motion between the transmitter and
>receiver, causing shorter or longer wavelengths to be received by the
>receiver.

Exactly right. I think what's confusing about FM is that it
*doesn't* require a "non-linear" (in the usual common useage)
term. No kinks or bends in the in-vs-out curve.

It's constructed completely out of rotating vectors. PFM!

Chris Hornbeck

[Chris Hornbeck]

On Fri, 13 Aug 2004 08:13:08 -0400, "Arny Krueger" >
wrote:

>Doppler is nonlinear distortion. It creates signals at additional
>frequencies that were not part of the original signal.

>Doppler is the result of relatively motion between the transmitter and
>receiver, causing shorter or longer wavelengths to be received by the
>receiver.

Exactly right. I think what's confusing about FM is that it
*doesn't* require a "non-linear" (in the usual common useage)
term. No kinks or bends in the in-vs-out curve.

It's constructed completely out of rotating vectors. PFM!

Chris Hornbeck

[Phil Allison]

"Chris Hornbeck"
"Arny Krueger"

> >Doppler is nonlinear distortion. It creates signals at additional
> >frequencies that were not part of the original signal.
>
> >Doppler is the result of relatively motion between the transmitter and
> >receiver, causing shorter or longer wavelengths to be received by the
> >receiver.

>
> Exactly right.


** The two paras are in direct contradiction.

Hornbeck would have done well in Orwell's 1984.




............ Phil

[Phil Allison]

"Chris Hornbeck"
"Arny Krueger"

> >Doppler is nonlinear distortion. It creates signals at additional
> >frequencies that were not part of the original signal.
>
> >Doppler is the result of relatively motion between the transmitter and
> >receiver, causing shorter or longer wavelengths to be received by the
> >receiver.

>
> Exactly right.


** The two paras are in direct contradiction.

Hornbeck would have done well in Orwell's 1984.




............ Phil

[William Sommerwerck]

> Depends on the speaker. I think the Hill devices had a sheet of plasma
> in a magnetic field, and by shifting the magnetic field you could move
> the plasma forward and back and thereby move air with it. But I do recall
> another device that relied on changing ionization.

There was no magnetic field. The plasma was produced by RF excitation, and the
audio signal AM modulated it.

Dr. Hill told me that he had assumed the same as everyone else -- that the
plasma varied in volume with the modulation and "pushed" the air. He claimed
that a study of the thermodynamics of the system showed otherwise.

[William Sommerwerck]

> Depends on the speaker. I think the Hill devices had a sheet of plasma
> in a magnetic field, and by shifting the magnetic field you could move
> the plasma forward and back and thereby move air with it. But I do recall
> another device that relied on changing ionization.

There was no magnetic field. The plasma was produced by RF excitation, and the
audio signal AM modulated it.

Dr. Hill told me that he had assumed the same as everyone else -- that the
plasma varied in volume with the modulation and "pushed" the air. He claimed
that a study of the thermodynamics of the system showed otherwise.

[William Sommerwerck]

What is it with you two? When I make ad-hominem attacks on Arny, at least
they're global metaphysical/philosophical attacks.

[William Sommerwerck]

What is it with you two? When I make ad-hominem attacks on Arny, at least
they're global metaphysical/philosophical attacks.

[Bob Cain]

Carey Carlan wrote:

> Your argument assumes that the microphone diaphragm moves the same extent
> during recording as the speaker does during playback.

Another way of pointing out that it wouldn't be a linear
phenomenon. If it were it would scale with everything else.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Carey Carlan wrote:

> Your argument assumes that the microphone diaphragm moves the same extent
> during recording as the speaker does during playback.

Another way of pointing out that it wouldn't be a linear
phenomenon. If it were it would scale with everything else.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:

>>>In the case of lightning, isn't it the thermal expansion
>>>of the air that causes the sound of thunder?
>
>
>>Yes, but it isn't what makes an ion speaker speak. :-)
>
>
> Yes, it is. Ask Dr. Hill.

Don't know him. Did he write the working principle up?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:

>>>In the case of lightning, isn't it the thermal expansion
>>>of the air that causes the sound of thunder?
>
>
>>Yes, but it isn't what makes an ion speaker speak. :-)
>
>
> Yes, it is. Ask Dr. Hill.

Don't know him. Did he write the working principle up?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:


> I, too, dislike appealing to authority. But I've met Dr. Hill, talked with him
> at length, and he's no dummy. Ionic speakers do NOT work by "pushing" the air in
> front of them. The sound is a PV = nRT effect, where changes in temperature
> produce pressure changes.
>
> Dr. Hill also developed what he called a "toaster woofer," nichrome wire strung
> around a heat-resistant form. He claimed that the reason toasters hum could be
> used to reproduce sound. I never saw a demo, though.

The clasic ionic speaker is the "flame speaker" to which a
HV signal is placed across the flame. That is an
electrostic and not a thermal drive. If he found a way to
modulate the temperature of air that rapidly somehow with
RF, which is typically just the means of stripping off the
electrons to ionize it, then that's really something. I
just don't believe it until I see a more in depth justification.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:


> I, too, dislike appealing to authority. But I've met Dr. Hill, talked with him
> at length, and he's no dummy. Ionic speakers do NOT work by "pushing" the air in
> front of them. The sound is a PV = nRT effect, where changes in temperature
> produce pressure changes.
>
> Dr. Hill also developed what he called a "toaster woofer," nichrome wire strung
> around a heat-resistant form. He claimed that the reason toasters hum could be
> used to reproduce sound. I never saw a demo, though.

The clasic ionic speaker is the "flame speaker" to which a
HV signal is placed across the flame. That is an
electrostic and not a thermal drive. If he found a way to
modulate the temperature of air that rapidly somehow with
RF, which is typically just the means of stripping off the
electrons to ionize it, then that's really something. I
just don't believe it until I see a more in depth justification.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Arny Krueger]

"Chris Hornbeck" > wrote in message


> On Fri, 13 Aug 2004 08:13:08 -0400, "Arny Krueger" >
> wrote:

>> Doppler is nonlinear distortion. It creates signals at additional
>> frequencies that were not part of the original signal.

>> Doppler is the result of relative motion between the transmitter
>> and receiver, causing shorter or longer wavelengths to be received
>> by the receiver.

> Exactly right.

Thank you.

> I think what's confusing about FM is that it
> *doesn't* require a "non-linear" (in the usual common useage)
> term. No kinks or bends in the in-vs-out curve.

The usual terminology has something to with Doppler not being dependent on
component properties (other than location!) that change with changes in the
signal.

> It's constructed completely out of rotating vectors. PFM!

And given that relative motion is vector quantity...

[Arny Krueger]

"Chris Hornbeck" > wrote in message


> On Fri, 13 Aug 2004 08:13:08 -0400, "Arny Krueger" >
> wrote:

>> Doppler is nonlinear distortion. It creates signals at additional
>> frequencies that were not part of the original signal.

>> Doppler is the result of relative motion between the transmitter
>> and receiver, causing shorter or longer wavelengths to be received
>> by the receiver.

> Exactly right.

Thank you.

> I think what's confusing about FM is that it
> *doesn't* require a "non-linear" (in the usual common useage)
> term. No kinks or bends in the in-vs-out curve.

The usual terminology has something to with Doppler not being dependent on
component properties (other than location!) that change with changes in the
signal.

> It's constructed completely out of rotating vectors. PFM!

And given that relative motion is vector quantity...

[Arny Krueger]

"Phil Allison" > wrote in message


> "Chris Hornbeck"

> "Arny Krueger"

>>> Doppler is nonlinear distortion. It creates signals at additional
>>> frequencies that were not part of the original signal.

>>> Doppler is the result of relative motion between the transmitter
>>> and receiver, causing shorter or longer wavelengths to be received
>>> by the receiver.

>> Exactly right.

> ** The two paras are in direct contradiction.

Please explain.

[Arny Krueger]

"Phil Allison" > wrote in message


> "Chris Hornbeck"

> "Arny Krueger"

>>> Doppler is nonlinear distortion. It creates signals at additional
>>> frequencies that were not part of the original signal.

>>> Doppler is the result of relative motion between the transmitter
>>> and receiver, causing shorter or longer wavelengths to be received
>>> by the receiver.

>> Exactly right.

> ** The two paras are in direct contradiction.

Please explain.

[William Sommerwerck]

> If he [Dr. Hill] found a way to modulate the temperature
> of air that rapidly somehow with RF, which is typically
> just the means of stripping off the electrons to ionize it,
> then that's really something.

He didn't "find" a way to do it. It turns out that that's the way an ionic
speaker (such as the Ionovac) works.

[William Sommerwerck]

> If he [Dr. Hill] found a way to modulate the temperature
> of air that rapidly somehow with RF, which is typically
> just the means of stripping off the electrons to ionize it,
> then that's really something.

He didn't "find" a way to do it. It turns out that that's the way an ionic
speaker (such as the Ionovac) works.

[Bob Cain]

Arny Krueger wrote:

[snip]

>
> enjoy! ;-)

Wish I could, a few of them sound like they could be
contenders. Do you have these CD's, Arny.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Arny Krueger wrote:

[snip]

>
> enjoy! ;-)

Wish I could, a few of them sound like they could be
contenders. Do you have these CD's, Arny.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:

> "Bob Cain"

>
>>Ok. The false assumption is that the pressure wave created
>>by a piston is proportional to its acceleration. It isn't;
>>it's proprotional to the piston velocity.
>
> ** You have evidence ????

Better than that, I have a proof by the principle of
reciprocity (not at all the same as analogy since it only
considers the actual system in question.) If you missed it,
I'll be happy to repeat it.

>>Didn't I explain what a linear system is in a prior post?
>
> ** No interest to me or anyone else what YOU decide the laws of nature
> are.

Ummm, don't know what to say to that. It's not just what I
believe, it is the agreed definition within the entire field
of linear systems. It's in lotsa books, textbooks.

>>Nothing that produces "frequencies" that aren't in what's
>>driving it is linear.
>
> ** Pure gobbledegook.

Pure and unadulterated truth, like it or not.

>
> Try defining your terms in a consistent and familiar manner.

Try doing some study so I don't have to hand feed you the
fundamentals and then argue with you about them.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:

> "Bob Cain"

>
>>Ok. The false assumption is that the pressure wave created
>>by a piston is proportional to its acceleration. It isn't;
>>it's proprotional to the piston velocity.
>
> ** You have evidence ????

Better than that, I have a proof by the principle of
reciprocity (not at all the same as analogy since it only
considers the actual system in question.) If you missed it,
I'll be happy to repeat it.

>>Didn't I explain what a linear system is in a prior post?
>
> ** No interest to me or anyone else what YOU decide the laws of nature
> are.

Ummm, don't know what to say to that. It's not just what I
believe, it is the agreed definition within the entire field
of linear systems. It's in lotsa books, textbooks.

>>Nothing that produces "frequencies" that aren't in what's
>>driving it is linear.
>
> ** Pure gobbledegook.

Pure and unadulterated truth, like it or not.

>
> Try defining your terms in a consistent and familiar manner.

Try doing some study so I don't have to hand feed you the
fundamentals and then argue with you about them.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Chris Hornbeck wrote:

>
> Exactly right. I think what's confusing about FM is that it
> *doesn't* require a "non-linear" (in the usual common useage)
> term. No kinks or bends in the in-vs-out curve.
>
> It's constructed completely out of rotating vectors. PFM!

Chris, you've said this a couple of times. Which of the
references, that I haven't yet looked at, analyzes it in
those terms?


Bo
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Chris Hornbeck wrote:

>
> Exactly right. I think what's confusing about FM is that it
> *doesn't* require a "non-linear" (in the usual common useage)
> term. No kinks or bends in the in-vs-out curve.
>
> It's constructed completely out of rotating vectors. PFM!

Chris, you've said this a couple of times. Which of the
references, that I haven't yet looked at, analyzes it in
those terms?


Bo
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Chris Hornbeck wrote:

> On Fri, 13 Aug 2004 01:56:22 -0700, Bob Cain
> > wrote:
>
>
>>Yeah, I'm hoping for citations that provide a complete
>>theory for the effect from which the result of any driving
>>point velocity or pressure can be predicted. There is no
>>good reason why this doesn't exist except possibly for one.
>
> I'm puzzled why you're unconvinced by an argument from
> Terman, rotating vectors and such like. Doesn't the diaphragm
> itself contain enough information (for a fixed listener?)

As I said in another post, I have missed that reference.
Could you give it again, please.

>>Everything is really subjective to this point without the
>>requisite separation of variables.
>
> So, ignoring the side arguments of audibility and testing
> procedures, is your quest located at the diaphragm-air
> translation?

Precisely. I seek a general theory of what happens there
and how it results in the propegation of a sound wave. I
think it's simple and we already have it. I've stated it
(again today in response to George Perfect in Mike Rivers'
Doppler thread) but it doesn't admit of anything like
"Doppler distortion."


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Chris Hornbeck wrote:

> On Fri, 13 Aug 2004 01:56:22 -0700, Bob Cain
> > wrote:
>
>
>>Yeah, I'm hoping for citations that provide a complete
>>theory for the effect from which the result of any driving
>>point velocity or pressure can be predicted. There is no
>>good reason why this doesn't exist except possibly for one.
>
> I'm puzzled why you're unconvinced by an argument from
> Terman, rotating vectors and such like. Doesn't the diaphragm
> itself contain enough information (for a fixed listener?)

As I said in another post, I have missed that reference.
Could you give it again, please.

>>Everything is really subjective to this point without the
>>requisite separation of variables.
>
> So, ignoring the side arguments of audibility and testing
> procedures, is your quest located at the diaphragm-air
> translation?

Precisely. I seek a general theory of what happens there
and how it results in the propegation of a sound wave. I
think it's simple and we already have it. I've stated it
(again today in response to George Perfect in Mike Rivers'
Doppler thread) but it doesn't admit of anything like
"Doppler distortion."


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Scott Dorsey]

Bob Cain > wrote:
>
>Precisely. I seek a general theory of what happens there
>and how it results in the propegation of a sound wave. I
>think it's simple and we already have it.

For the most part we have a pretty good notion. There are some boundary
areas with the very small objects that are a little doubtful (and Juha
Backman's paper on compression-induced distortion effects in microphones
is an example), but wave propagation was pretty well-explored by the
last turn of the century.

I've stated it
>(again today in response to George Perfect in Mike Rivers'
>Doppler thread) but it doesn't admit of anything like
>"Doppler distortion."

The Doppler issue isn't one of wave propagation at all, it's an issue
that results from the breakdown of reciprocity, where the motion of the
speaker to produce a given wave in air is different than the motion of
the microphone diaphragm that picked it up.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Bob Cain > wrote:
>
>Precisely. I seek a general theory of what happens there
>and how it results in the propegation of a sound wave. I
>think it's simple and we already have it.

For the most part we have a pretty good notion. There are some boundary
areas with the very small objects that are a little doubtful (and Juha
Backman's paper on compression-induced distortion effects in microphones
is an example), but wave propagation was pretty well-explored by the
last turn of the century.

I've stated it
>(again today in response to George Perfect in Mike Rivers'
>Doppler thread) but it doesn't admit of anything like
>"Doppler distortion."

The Doppler issue isn't one of wave propagation at all, it's an issue
that results from the breakdown of reciprocity, where the motion of the
speaker to produce a given wave in air is different than the motion of
the microphone diaphragm that picked it up.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Chris Hornbeck]

On Fri, 13 Aug 2004 11:13:42 -0700, Bob Cain
> wrote:

>> Yes, it is. Ask Dr. Hill.
>
>Don't know him. Did he write the working principle up?

He means Dr. ** Hill. He's got a daytime TV show that probably
gets around to the topic sometimes.

Chris Hornbeck

[Chris Hornbeck]

On Fri, 13 Aug 2004 11:13:42 -0700, Bob Cain
> wrote:

>> Yes, it is. Ask Dr. Hill.
>
>Don't know him. Did he write the working principle up?

He means Dr. ** Hill. He's got a daytime TV show that probably
gets around to the topic sometimes.

Chris Hornbeck

[Chris Hornbeck]

On Fri, 13 Aug 2004 14:30:08 -0700, Bob Cain
> wrote:

>> It's constructed completely out of rotating vectors. PFM!
>
>Chris, you've said this a couple of times. Which of the
>references, that I haven't yet looked at, analyzes it in
>those terms?

My Kyper _FM Simplified_ is out on loan, but should be back soon,
and I can give you a better pointer.

But for a heavy math guy like you, the Terman-level description
might be even better. His 1947 3rd ed. of _Radio Engineering_
chapter 9 section 5 has two equations applicable:

9.6 gives a description of instantaneous amplitude of a wave as
a function of angular velocities and frequencies, and

9.9 gives the Bessel function of the first kind expansion for the
sum of the two angles.

Chris Hornbeck

[Chris Hornbeck]

On Fri, 13 Aug 2004 14:30:08 -0700, Bob Cain
> wrote:

>> It's constructed completely out of rotating vectors. PFM!
>
>Chris, you've said this a couple of times. Which of the
>references, that I haven't yet looked at, analyzes it in
>those terms?

My Kyper _FM Simplified_ is out on loan, but should be back soon,
and I can give you a better pointer.

But for a heavy math guy like you, the Terman-level description
might be even better. His 1947 3rd ed. of _Radio Engineering_
chapter 9 section 5 has two equations applicable:

9.6 gives a description of instantaneous amplitude of a wave as
a function of angular velocities and frequencies, and

9.9 gives the Bessel function of the first kind expansion for the
sum of the two angles.

Chris Hornbeck

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
> >
> >>Ok. The false assumption is that the pressure wave created
> >>by a piston is proportional to its acceleration. It isn't;
> >>it's proprotional to the piston velocity.
> >
> > ** You have evidence ????
>
> Better than that, I have a proof by the principle of
> reciprocity (not at all the same as analogy since it only
> considers the actual system in question.) If you missed it,
> I'll be happy to repeat it.


** You have no proof - only your own a mad ideas.

Speaker cones reach their greatest velicities at low frequencies and large
excursions while making the same SPL as at higher frequencies with lower
velocities.


> > ** Dunno what you are on about - Doppler is a linear phenomenon, not
some kind of distortion product. It is simply the result of a moving source
> > creating longer or shorter wavelengths in the air than it would if
> > stationery.
>
>
> >>Didn't I explain what a linear system is in a prior post?
> >
> > ** No interest to me or anyone else what YOU decide the laws of
nature
> > are.
>
> Ummm, don't know what to say to that. It's not just what I
> believe, it is the agreed definition within the entire field
> of linear systems. It's in lotsa books, textbooks.


** You are seriously misquoting them.


> >>Nothing that produces "frequencies" that aren't in what's
> >>driving it is linear.
> >
> > ** Pure gobbledegook.
>
> Pure and unadulterated truth, like it or not.


** Proof by wild assertion saves much time - shame it is worthess.



.............. Phil

[Phil Allison]

"Bob Cain"
> Phil Allison wrote:
> >
> >>Ok. The false assumption is that the pressure wave created
> >>by a piston is proportional to its acceleration. It isn't;
> >>it's proprotional to the piston velocity.
> >
> > ** You have evidence ????
>
> Better than that, I have a proof by the principle of
> reciprocity (not at all the same as analogy since it only
> considers the actual system in question.) If you missed it,
> I'll be happy to repeat it.


** You have no proof - only your own a mad ideas.

Speaker cones reach their greatest velicities at low frequencies and large
excursions while making the same SPL as at higher frequencies with lower
velocities.


> > ** Dunno what you are on about - Doppler is a linear phenomenon, not
some kind of distortion product. It is simply the result of a moving source
> > creating longer or shorter wavelengths in the air than it would if
> > stationery.
>
>
> >>Didn't I explain what a linear system is in a prior post?
> >
> > ** No interest to me or anyone else what YOU decide the laws of
nature
> > are.
>
> Ummm, don't know what to say to that. It's not just what I
> believe, it is the agreed definition within the entire field
> of linear systems. It's in lotsa books, textbooks.


** You are seriously misquoting them.


> >>Nothing that produces "frequencies" that aren't in what's
> >>driving it is linear.
> >
> > ** Pure gobbledegook.
>
> Pure and unadulterated truth, like it or not.


** Proof by wild assertion saves much time - shame it is worthess.



.............. Phil

[Chris Hornbeck]

On 13 Aug 2004 22:20:04 -0400, (Scott Dorsey) wrote:

>The Doppler issue isn't one of wave propagation at all, it's an issue
>that results from the breakdown of reciprocity, where the motion of the
>speaker to produce a given wave in air is different than the motion of
>the microphone diaphragm that picked it up.

I have a theory! This is at least (couldn't really follow it all)
the third major paradigm shift in this discussion. So:

1. Bob Cain, notorious trickster, bon vivant and fan of Albert
Einstein, posts a challenging conceptual thread in August 2004.

2. One hundred years ago, in a land far, far away, an unknown
clerk with a day job in the Zurich patent office was thinking
about train whistles, the much earlier Michealson-Morley C
experiments, and Lorentz's recent E=MC^2 conclusions.

3. Said clerk decides, hey! I could get the babes if I just
pretended that all this hockus-pockus was true. Turns out to be
right! Who knew?! Rock-n-Roll.

4. Said notorious trickster tosses bomb into newsgroup as part
homage, part Summer Blockbuster.

5. Lots is learned, (He who cannot be named) contributes (!),
some new blood arrives. All good.

"That is my theory, and what it is too." - Anne Elk

Chris Hornbeck

[Chris Hornbeck]

On 13 Aug 2004 22:20:04 -0400, (Scott Dorsey) wrote:

>The Doppler issue isn't one of wave propagation at all, it's an issue
>that results from the breakdown of reciprocity, where the motion of the
>speaker to produce a given wave in air is different than the motion of
>the microphone diaphragm that picked it up.

I should also have said in my earlier frivolous post that this is
the most elegant viewpoint I've yet heard. It includes everything
that matters and excludes the Ghafla.

Chris Hornbeck

[Bob Cain]

Scott Dorsey wrote:

> The Doppler issue isn't one of wave propagation at all, it's an issue
> that results from the breakdown of reciprocity, where the motion of the
> speaker to produce a given wave in air is different than the motion of
> the microphone diaphragm that picked it up.

I'd need to see a real good reason for reciprocity to
breakdown. Hand waving about waves riding waves just
doesn't hack it I'm afraid.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Phil Allison wrote:

[some nonsense]

Go away, troll. Your utter ignorance is a heavy weight on
this discussion, and most it seems. You really enjoy that
don't you. No more for feed for ya, son.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Chris Hornbeck wrote:

> My Kyper _FM Simplified_ is out on loan, but should be back soon,
> and I can give you a better pointer.
>
> But for a heavy math guy like you, the Terman-level description
> might be even better. His 1947 3rd ed. of _Radio Engineering_
> chapter 9 section 5 has two equations applicable:
>
> 9.6 gives a description of instantaneous amplitude of a wave as
> a function of angular velocities and frequencies, and
>
> 9.9 gives the Bessel function of the first kind expansion for the
> sum of the two angles.

Chris, I'm a bit confused here. Is Termen's description
that of the basic principles of frequency modulation or does
he relate that to loudspeaker motion and show how it
produces it with mathematical rigor?

The question here is whether or not a loudspeaker comprises
a frequency modulator at all and if so, what's the full
mathematical description rigorously tied to physical principles.

Doesn't it puzzle you too that it hasn't been produced to
kill my thesis? If it exists and can predict the behavior
quantitatively that would pretty much put an end to it. It
hasn't been produced or referenced here or in any of the
physics or acoustics related forums I've asked.

I am persuaded that the absence of a theory in this case
provides at least one good theory for the absence of the
phenomenon.

That an ideal piston would move in some way in response to
an acoustic wave but not produce that wave when moved the
same way seems utterly absurd. I'm not up to it tonight but
I'll bet that reciprocity can be proven to be required by an
appeal to the conservation of energy.

I guess that is the final step of my argument, though, to
show on first principles that conservation of energy (or
some basic physical conservation law) requires the
reciprocity on which the argument is based. Heavy sigh.
That seems as obvious to me without proof as the argument
for "Doppler distortion" does to others. At least it
appears reasonably amenable to proof.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Chris Hornbeck]

On Fri, 13 Aug 2004 23:40:44 -0700, Bob Cain
> wrote:

>> The Doppler issue isn't one of wave propagation at all, it's an issue
>> that results from the breakdown of reciprocity, where the motion of the
>> speaker to produce a given wave in air is different than the motion of
>> the microphone diaphragm that picked it up.
>
>I'd need to see a real good reason for reciprocity to
>breakdown. Hand waving about waves riding waves just
>doesn't hack it I'm afraid.

But that's the thing I like best about it; it's an algebraic ratio
of diaphragm sizes divided by field strength.

Yes: everything moving has FM issues.

But: smaller things move less in the same field.

I'll have to get some sleep on this, but crudely: the originating
diaphragm must move (some) to do its job. The receiving diaphragm
must move (some less) to do its job.

Chris Hornbeck

[Chris Hornbeck]

On Sat, 14 Aug 2004 00:11:20 -0700, Bob Cain
> wrote:

>Chris, I'm a bit confused here. Is Termen's description
>that of the basic principles of frequency modulation or does
>he relate that to loudspeaker motion and show how it
>produces it with mathematical rigor?

Terman only describes the results, not the machinery. He
assumes that one believes the machinery to be applicable.
(Well, it is for an FM transmitter, so he's fairly confident!).


>The question here is whether or not a loudspeaker comprises
>a frequency modulator at all and if so, what's the full
>mathematical description rigorously tied to physical principles.

Can you accept that the (moving, of course) diaphragm
defines the system output? Or must we move further downstream?

If you can't accept the diaphragm's motion as definitive
then I'm lost. If you can, then we can move on to the receiving
diaphragm.

But if you can....



>Doesn't it puzzle you too that it hasn't been produced to
>kill my thesis? If it exists and can predict the behavior
>quantitatively that would pretty much put an end to it. It
>hasn't been produced or referenced here or in any of the
>physics or acoustics related forums I've asked.

OTOH, that's what makes a great topic. The easy stuff gets
laughed off and the impossible stuff gets bull****ted off.

But! the great stuff lies right under the surface. And so
encourages discussion. Everybody *thinks* they know how
transformers work....

But really, nobody does. Our intuitively useful models are,
not to put too fine a point on it, wrong. Tough titty; we
get along.

>I am persuaded that the absence of a theory in this case
>provides at least one good theory for the absence of the
>phenomenon.

Or: the theory exists someplace else. I just don't think
audio is the place to look. It's a radio theory.

>That an ideal piston would move in some way in response to
>an acoustic wave but not produce that wave when moved the
>same way seems utterly absurd. I'm not up to it tonight but
>I'll bet that reciprocity can be proven to be required by an
>appeal to the conservation of energy.

>I guess that is the final step of my argument, though, to
>show on first principles that conservation of energy (or
>some basic physical conservation law) requires the
>reciprocity on which the argument is based.

Do microphones exhibit FM distortion? If so, how much?
(See S. D. above)

>That seems as obvious to me without proof as the argument
>for "Doppler distortion" does to others. At least it
>appears reasonably amenable to proof.

The answer to Scott's posed question is simply "It's bigger."
The scale makes it significant.

Chris Hornbeck

[Arny Krueger]

"Chris Hornbeck" > wrote in message


> I'll have to get some sleep on this, but crudely: the originating
> diaphragm must move (some) to do its job. The receiving diaphragm
> must move (some less) to do its job.

If you had two diaphragms that had to move equal distances in the same
direction to accomplish their respective functions of receiving or sending,
there would be no Doppler distortion. We would be back to the listener
riding on the same train as the whistle.

[Arny Krueger]

"Bob Cain" > wrote in message


> If it exists and can predict the behavior
> quantitatively that would pretty much put an end to it. It
> hasn't been produced or referenced here or in any of the
> physics or acoustics related forums I've asked.

I believe that Goofball has the math and experimental data that does that.

[Scott Dorsey]

Bob Cain > wrote:
>Scott Dorsey wrote:
>
>> The Doppler issue isn't one of wave propagation at all, it's an issue
>> that results from the breakdown of reciprocity, where the motion of the
>> speaker to produce a given wave in air is different than the motion of
>> the microphone diaphragm that picked it up.
>
>I'd need to see a real good reason for reciprocity to
>breakdown. Hand waving about waves riding waves just
>doesn't hack it I'm afraid.

It's in the nature of speaker cabinets. Look at the woofer excursion on
a 20 Hz note vs. a 50 Hz note. Now look at what happens to a microphone
given the same two notes. The ratios are not even a little bit the same.
You can plug-and-chug with the formulae in the Dickason book if you want
to know the maximum excursion of a given driver in a given cabinet at a
given frequency.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison]

"Bob Cain"
>
>
> Phil Allison wrote:
>
> [some nonsense]


** Some very much sense was rudely snipped by a NG ****wit who makes the
world's perpetual motion imbeciles look sane.






........... Phil

[William Sommerwerck]

>> If it exists and can predict the behavior quantitatively that
>> would pretty much put an end to it. It hasn't been produced
>> or referenced here or in any of the physics or acoustics
>> related forums I've asked.

> I believe that Goofball has the math and experimental data that does that.

Are you talking audibility or existence?


Several days ago I reduced the issue to a simple thought-experiment -- given a
driver producing a high frequency, is there a fundamental difference between
moving the driver as a whole at a much lower frequency and moving the cone
itself at a much lower frequency?

If there is none, then Doppler distortion exists. If there is, then it might or
might not.

I understand (and sympathize with) Bob's desire for a mathematical treatment.
But I much prefer the "clever insight" <ahem> that points to the real issue, and
cuts the Gordian knot.

[William Sommerwerck]

> Speaker cones reach their greatest velicities at low frequencies
> and large excursions while making the same SPL as at higher
> frequencies with lower velocities.

Uh... If you double the frequency and halve the excursion, you have exactly the
same velocity.

Electrodynamic speakers are velocity devices.

[Goofball_star_dot_etal]

On Sat, 14 Aug 2004 06:27:18 -0700, "William Sommerwerck"
> wrote:

>> Speaker cones reach their greatest velicities at low frequencies
>> and large excursions while making the same SPL as at higher
>> frequencies with lower velocities.
>
>Uh... If you double the frequency and

> halve the excursion,

Oops-a-daisy.

>y ou have exactly the
>same velocity.
>
>Electrodynamic speakers are velocity devices.
>

[Phil Allison]

"William Sommerwerck"
>>
> > Speaker cones reach their greatest velicities at low frequencies
> > and large excursions while making the same SPL as at higher
> > frequencies with lower velocities.
>
> Uh... If you double the frequency and halve the excursion, you have
exactly the
> same velocity.


** But not the same SPL.

" F = mA " rules.





............ Phil

[William Sommerwerck]

> ** But not the same SPL.
>
> " F = mA " rules.

No, I believe you do have the same SPL. Correct me if I'm wrong, but doubling
the frequency also doubles the acoustic impedance (???) and you get the same
power transfer to the air.

I'm weak on this. Somebody fill me in.

[Goofball_star_dot_etal]

On Sat, 14 Aug 2004 07:39:18 -0700, "William Sommerwerck"
> wrote:

>> ** But not the same SPL.
>>
>> " F = mA " rules.
>
>No, I believe you do have the same SPL. Correct me if I'm wrong, but doubling
>the frequency also doubles the acoustic impedance (???) and you get the same
>power transfer to the air.
>
>I'm weak on this. Somebody fill me in.
>
http://www.google.com/groups?selm=EKMtE0.G1w%40world.std.com&output=gplain

[Arny Krueger]

"William Sommerwerck" > wrote in message

>> ** But not the same SPL.
>>
>> " F = mA " rules.
>
> No, I believe you do have the same SPL. Correct me if I'm wrong, but
> doubling the frequency also doubles the acoustic impedance (???) and
> you get the same power transfer to the air.
>
> I'm weak on this. Somebody fill me in.

Goofball's cite of Pierce's article is the real thing.

All other things being equal, excursion goes up by four when the frequency
goes down by two.

[Arny Krueger]

"William Sommerwerck" > wrote in message

>>> If it exists and can predict the behavior quantitatively that
>>> would pretty much put an end to it. It hasn't been produced
>>> or referenced here or in any of the physics or acoustics
>>> related forums I've asked.
>
>> I believe that Goofball has the math and experimental data that does
>> that.
>
> Are you talking audibility or existence?

Existence.

> Several days ago I reduced the issue to a simple thought-experiment
> -- given a driver producing a high frequency, is there a fundamental
> difference between moving the driver as a whole at a much lower
> frequency and moving the cone itself at a much lower frequency?

I thought it was a great question with an obvious answer.

> If there is none, then Doppler distortion exists. If there is, then
> it might or might not.

There is none from the perspective of the listener.

> I understand (and sympathize with) Bob's desire for a mathematical
> treatment. But I much prefer the "clever insight" <ahem> that points
> to the real issue, and cuts the Gordian knot.

Well yesterday I cited about a jillion AES articles that are all positive
for Doppler distortion in speakers, but generally negative for it being a
serious audible problem, if they grant an opinion on that topic at all.

[Ben Bradley]

On Sat, 14 Aug 2004 00:11:20 -0700, Bob Cain
> wrote:

>...

>The question here is whether or not a loudspeaker comprises
>a frequency modulator at all and if so, what's the full
>mathematical description rigorously tied to physical principles.
>
>Doesn't it puzzle you too that it hasn't been produced to
>kill my thesis? If it exists and can predict the behavior
>quantitatively that would pretty much put an end to it. It
>hasn't been produced or referenced here or in any of the
>physics or acoustics related forums I've asked.
>
>I am persuaded that the absence of a theory

The absence of a theory? What would a theory look like that would
convince you? I've seen some good arguments here and have tried to
present some on my own...

>in this case
>provides at least one good theory for the absence of the
>phenomenon.

Here's my attempt at something almost semi-rigorous. It has
equations, so maybe that will help convince you. :)

H = frequency of high-pitch tone
L = frequency of low-pitch tone
w = 2 pi * t generally called omega and used a conversion factor
from cycles to radians, the 'natural' unit for trig functions.
t = time, a continuously increasing value.

From those you can surely come up with this equation of the voltage
that would be put across the terminals of a speaker to generate these
pitches:

voltage = sin (wH) + sin (wL)

(there's of course a gain constant multiplier in front of each sin,
but we'll set them to 1 to keep things simple)
Presuming the loudspeaker (or driver, or whatever you call it) is
perfectly linear, the voice coil will move in proportion to the
voltage across it and its position .. well, actually, at frequencies
above resonance, I think it's the force the voice coil pushes with, or
the pressure the cone pushes on the air, that is proportional to the
impressed boltage, but regardless, we agree that it's all linear (that
all else the same, a higher voltage gives a proportionally higher
amplitude) in this theoretically perfect speaker driver.

pressure = sin (wH) + sin (wL)

where of course "pressure" is defined as relative to the ambient
air pressure, which is considered the zero reference point.

Put a microphone at some distance, maybe 10cm from the speaker.
Suppose the low frequency signal causes a total cone displacement of
10mm (5mm toward the mic, and 5mm away from the mic, in reference to
the cone's rest position). The high tone is also present, but for the
reasons given in the previous paragraph, it moves the cone a much
smaller distance (maybe .05mm), which we will ignore for the moment.
This means that at the positive peak of the low tone, the cone (which
is the source of the high tone - do we agree with that?) is closer to
the microphone. Due to the finite speed of sound, the mic picks up the
high tone in less time than when the cone is in its rest position, so
the high tone is phase-advance at the mic. Likewise at the negative
peak of the low tone, the distance between the cone and the mic is
greater than at rest position, so the high tone is phase-retarded at
the mic.
So the phase of the high tone as picked up by the (stationary) mic
is phase-modulated by the low pitch, and the formula becomes:

pressure = sin (wH + k * sin (wL)) + sin (wL)

where K is a constant that depends on (among other things) the
speed of sound. (It would be an inverse relationship - the faster the
speed of sound, the lower the value of k).

To truly complete the model, we should also indicate the phase
modulation of the low tone by the high tone (the 0.05mm distance I
mention above):

pressure = sin (wH + k * sin (wL)) + sin (wL + k2 * sin (wH))

where k2 is another constant similar to k (it should actually be
the same constant with a frequency dependence).

Of course, phase modulation, while not being the same as frequency
modulation, is equivalent. IIRC, it only takes an integral or a
derivative (of the modulating signal) to convert from one to the
other.

If you actually run this formula through something that generates
..wav files, small values of k amd k2 (perhaps barely audible, if at
all, compared to a value of 0) will give something similar to what a
full-range driver will do, and larger values will sound like a patch
on a Yamaha DX series synth (if you really want it to sound cool, have
k and k2 decrease exponentially). So to simulate a speaker, keep the
numbers low.

So that's my "theory" (I hesitate to use the word because there are
so many definitions, and I'm not sure any of them are right for this)
of FM in loudspeaker drivers.

If that doesn't convince you, I've got a boat oar in the water
making waves analogy, then I'll suggest you physically connect a train
whistle to a speaker cone... :)

>That an ideal piston would move in some way in response to
>an acoustic wave but not produce that wave when moved the
>same way seems utterly absurd. I'm not up to it tonight but
>I'll bet that reciprocity can be proven to be required by an
>appeal to the conservation of energy.
>
>I guess that is the final step of my argument, though, to
>show on first principles that conservation of energy (or
>some basic physical conservation law) requires the
>reciprocity on which the argument is based. Heavy sigh.
>That seems as obvious to me without proof as the argument
>for "Doppler distortion" does to others. At least it
>appears reasonably amenable to proof.
>
>
>Bob

-----
http://mindspring.com/~benbradley

[Bob Cain]

Chris Hornbeck wrote:

> Can you accept that the (moving, of course) diaphragm
> defines the system output? Or must we move further downstream?
>
> If you can't accept the diaphragm's motion as definitive
> then I'm lost. If you can, then we can move on to the receiving
> diaphragm.
>
> But if you can....

Yes, I can. The question is what that motion does to the
air in front of it.

>>Doesn't it puzzle you too that it hasn't been produced to
>>kill my thesis? If it exists and can predict the behavior
>>quantitatively that would pretty much put an end to it. It
>>hasn't been produced or referenced here or in any of the
>>physics or acoustics related forums I've asked.
>
>
> OTOH, that's what makes a great topic. The easy stuff gets
> laughed off and the impossible stuff gets bull****ted off.

LOL! That's the thing. If it exists, it shouldn't take a
John Baez or an Ed Whitten (prominent mathematical
physicists) to write it down.

> Our intuitively useful models are,
> not to put too fine a point on it, wrong. Tough titty; we
> get along.

All too often, and they can be very seductive too.


>>I am persuaded that the absence of a theory in this case
>>provides at least one good theory for the absence of the
>>phenomenon.
>
>
> Or: the theory exists someplace else. I just don't think
> audio is the place to look. It's a radio theory.

It's supposedly an acoustics phenomenon which is a branch of
classical mechanics. I've inquired of those community's
usenet presence and no answer has been forthcoming in those
forums either. I'm fair to middlin with physics myself
having degrees in both EE and Engineering Physics and
looking up close at it, nothing emerges but the simple
linear transmission of energy from piston to air.

> Do microphones exhibit FM distortion? If so, how much?
> (See S. D. above)

Dunno what the lore says but my analysis says no more so
than speakers, which is zero.

>
>
>>That seems as obvious to me without proof as the argument
>>for "Doppler distortion" does to others. At least it
>>appears reasonably amenable to proof.
>
>
> The answer to Scott's posed question is simply "It's bigger."
> The scale makes it significant.

Can't see any basis in physics for that. Seems to be
another of those intuitive things that can't really be
justified when push comes to shove. (With all due respect,
Scott.)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:

> Several days ago I reduced the issue to a simple thought-experiment -- given a
> driver producing a high frequency, is there a fundamental difference between
> moving the driver as a whole at a much lower frequency and moving the cone
> itself at a much lower frequency?

Not even sure the thought experiment casts any light on the
problem.

>
> If there is none, then Doppler distortion exists. If there is, then it might or
> might not.

If and only if the applied reasoning proves correct. I
don't think it does. I've given another line of reasoning
that shows conclusively that it doesn't exist if the law of
reciprocity applies to acoustic phenomenon. I see
absolutely no reason in physics why it shouldn't but that
remains to be proven or if that fails what law replaces it
that yields this "Doppler distortion."

>
> I understand (and sympathize with) Bob's desire for a mathematical treatment.
> But I much prefer the "clever insight" <ahem> that points to the real issue, and
> cuts the Gordian knot.
>

I've begun to think that the problem with the intuitive
description, that is so seductive, boils down to the belief
that a signal is physically made up of sinusoids and then
drawing false conclusions from that false belief.

While it's a whole 'nother argument that need not be taken
up here, a physical signal is no more composed of complex
exponentials (sins with phase) than it is of wavelets which
offer an infinite number of equivalent orthogonal basis
sets. The physical signal is what it is, no more, no less.
Fourier analysis isn't about physical reality, it's about
a mathematical tool that can, in the proper circumstances,
give insight and calculational advantage.

As such, if it exists, the phenomenon should be describable
without appeal to fourier analysis and that description
should yield quantifiable predictions that apply to any
signal. So far as I can determine, no such description
exists. Don't you find that puzzling? As I've said before,
this isn't string theory and shouldn't require a John Baez
or Ed Whitten to figure out.

John and I were close friends with frequent face time once
but that's been somewhat distanced by time and geography.
I'm tempted to ask him for his analysis of this but his
prominence has so skyrocketed since those days and our
friendship so lapsed that I am hesitant to even approach him
with something so trivial now. "I know I haven't been in
touch in many years, John, but I need you now to settle a
trivial classical physics argument", somehow doesn't sit
well with me. Besides, he'd probably just tell me "Bob,
that's something you shouldn't need my help with." He's
known for that. :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Scott Dorsey wrote:

> It's in the nature of speaker cabinets.

Scott, the intuitive argument commonly presented to justify
"Doppler distortion" doesn't appeal in any way to cabinets
or other imperfections in the emitter. It is described as a
mechanism that occurs at the piston/air interface regardless
of how that piston gets driven.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Arny Krueger wrote:

> If you had two diaphragms that had to move equal distances in the same
> direction to accomplish their respective functions of receiving or sending,
> there would be no Doppler distortion. We would be back to the listener
> riding on the same train as the whistle.

Bingo. <Bob leaves the stage to thunderous applause> :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

William Sommerwerck wrote:

>>Speaker cones reach their greatest velicities at low frequencies
>>and large excursions while making the same SPL as at higher
>>frequencies with lower velocities.
>
>
> Uh... If you double the frequency and halve the excursion, you have exactly the
> same velocity.
>
> Electrodynamic speakers are velocity devices.

Hey, William, we agree on something. I think the occasion
warrents a party. But then, I think that of most occasions.
:-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[William Sommerwerck]

>> Several days ago I reduced the issue to a simple thought-experiment --
>> given a driver producing a high frequency, is there a fundamental
>> difference between moving the driver as a whole at a much lower
>> frequency and moving the cone itself at a much lower frequency?

> Not even sure the thought experiment casts any light on the
> problem.

Then you need to rethink it. It cuts right to the heart of the issue.


> I've begun to think that the problem with the intuitive
> description, that is so seductive, boils down to the belief
> that a signal is physically made up of sinusoids and then
> drawing false conclusions from that false belief.

The Principle of Superposition states that, in a linear system, the output for a
complex input is equal to the simple sum of the outputs for the sinusoidal
inputs that make up the complex input.

This is true for the cone motion, but it says nothing about the medium in front
of the cone.


> As such, if it exists, the phenomenon should be describable
> without appeal to fourier analysis and that description
> should yield quantifiable predictions that apply to any
> signal. So far as I can determine, no such description
> exists. Don't you find that puzzling? As I've said before,
> this isn't string theory and shouldn't require a John Baez
> or Ed Whitten to figure out.

You're confusing the motion of the cone with the motion of the air in front of
it. They're not necessarily the same thing.

[Bob Cain]

William Sommerwerck wrote:

>> ** But not the same SPL.
>>
>> " F = mA " rules.
>
>
> No, I believe you do have the same SPL. Correct me if I'm wrong, but doubling
> the frequency also doubles the acoustic impedance (???) and you get the same
> power transfer to the air.
>
> I'm weak on this. Somebody fill me in.

Sound pressure emitted by a piston is proportional to and in
phase with its velocity. Piston velocity alone determines SPL.

The F = mA applies to what happens to a piston with mass m
when a force F is applied to it in the absence of air. It
doesn't say anything about what happens to air in response
to the motion of a piston. That's independant of how the
piston gets its motion.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Bob Cain wrote:

>
> I've begun to think that the problem with the intuitive description,
> that is so seductive, boils down to the belief that a signal is
> physically made up of sinusoids and then drawing false conclusions from
> that false belief.
>
> While it's a whole 'nother argument that need not be taken up here, a
> physical signal is no more composed of complex exponentials (sins with
> phase) than it is of wavelets which offer an infinite number of
> equivalent orthogonal basis sets. The physical signal is what it is, no
> more, no less. Fourier analysis isn't about physical reality, it's
> about a mathematical tool that can, in the proper circumstances, give
> insight and calculational advantage.

While I will maintain until the end that the last paragraph
is true, I see that the consideration is a dead end. It's
much simpler than that.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Ben Bradley wrote:


> Put a microphone at some distance, maybe 10cm from the speaker.
> Suppose the low frequency signal causes a total cone displacement of
> 10mm (5mm toward the mic, and 5mm away from the mic, in reference to
> the cone's rest position). The high tone is also present, but for the
> reasons given in the previous paragraph, it moves the cone a much
> smaller distance (maybe .05mm), which we will ignore for the moment.
> This means that at the positive peak of the low tone, the cone (which
> is the source of the high tone - do we agree with that?) is closer to
> the microphone. Due to the finite speed of sound, the mic picks up the
> high tone in less time than when the cone is in its rest position, so
> the high tone is phase-advance at the mic. Likewise at the negative
> peak of the low tone, the distance between the cone and the mic is
> greater than at rest position, so the high tone is phase-retarded at
> the mic.

Here is the problem. Since the distance between driver and
detector is actually the distance from the rest position of
the driver to the detector, which is true because the driver
face is riding the wave it creates, there is really no phase
modulation because there is no distance modulation.

Any math that starts from the assumption that the distance
from the driver to the detector is the instantaneous
position of the piston will end at the wrong place.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Phil Allison]

"Goofball_star_dot_etal"
> On Sat, 14 Aug 2004 07:39:18 -0700, "William Sommerwerck"
> > wrote:
>
> >> ** But not the same SPL.
> >>
> >> " F = mA " rules.
> >
> >No, I believe you do have the same SPL. Correct me if I'm wrong, but
doubling
> >the frequency also doubles the acoustic impedance (???) and you get the
same
> >power transfer to the air.
> >
> >I'm weak on this. Somebody fill me in.
> >
> http://www.google.com/groups?selm=EKMtE0.G1w%40world.std.com&output=gplain


" Above resonance, where the system is mass controlled, for a given drive
level, acceleration is
constant with frequency. Integrate that w.r.t. frequency and you find the
velocity then goes as the inverse frequency. Now integrate the velocity
w.r.t. frequency and you then find that displacement goes as the inverse
square of frequency. "



** QED



............... Phil

[Phil Allison]

"Bob Cain"
>
> William Sommerwerck wrote:
>
> >> ** But not the same SPL.
> >>
> >> " F = mA " rules.
> >
> >
> > No, I believe you do have the same SPL. Correct me if I'm wrong, but
doubling
> > the frequency also doubles the acoustic impedance (???) and you get the
same
> > power transfer to the air.
> >
> > I'm weak on this. Somebody fill me in.
>
> Sound pressure emitted by a piston is proportional to and in
> phase with its velocity. Piston velocity alone determines SPL.


** Mr Cain has applied Goebbel's theories of propaganda to science.


>
> The F = mA applies to what happens to a piston with mass m
> when a force F is applied to it in the absence of air.


** It also applies to a speaker cone ( above resonance) in the presence of
air.



> It doesn't say anything about what happens to air in response
> to the motion of a piston. That's independant of how the
> piston gets its motion.


** Purest gobbledegook.



............ Phil

[Phil Allison]

"Bob Cain"
>
>
> William Sommerwerck wrote:
>
> >>Speaker cones reach their greatest velicities at low frequencies
> >>and large excursions while making the same SPL as at higher
> >>frequencies with lower velocities.
> >
> >
> > Uh... If you double the frequency and halve the excursion, you have
exactly the
> > same velocity.
> >
> > Electrodynamic speakers are velocity devices.
>
> Hey, William, we agree on something.



** LOL




............. Phil

[Phil Allison]

"Bob Cain"
>
>
> Ben Bradley wrote:
>
>
> > Put a microphone at some distance, maybe 10cm from the speaker.
> > Suppose the low frequency signal causes a total cone displacement of
> > 10mm (5mm toward the mic, and 5mm away from the mic, in reference to
> > the cone's rest position). The high tone is also present, but for the
> > reasons given in the previous paragraph, it moves the cone a much
> > smaller distance (maybe .05mm), which we will ignore for the moment.
> > This means that at the positive peak of the low tone, the cone (which
> > is the source of the high tone - do we agree with that?) is closer to
> > the microphone. Due to the finite speed of sound, the mic picks up the
> > high tone in less time than when the cone is in its rest position, so
> > the high tone is phase-advance at the mic. Likewise at the negative
> > peak of the low tone, the distance between the cone and the mic is
> > greater than at rest position, so the high tone is phase-retarded at
> > the mic.
>
> Here is the problem. Since the distance between driver and
> detector is actually the distance from the rest position of
> the driver to the detector, which is true because the driver
> face is riding the wave it creates, there is really no phase
> modulation because there is no distance modulation.


** The low frequency tone changes the effective rest position of the driver
for the high frequency tone. The simplest test set up will show that the
time of arrival is being modulated and hence creating varying phase shift in
the high tone.

You only need to synch the scope's time base to a frequency source and watch
the phase change on the screen as a mic is moved near a speaker fed the same
frequency.

Add a low frequency into the game and the phase of the high one shimmers in
proportion to the **excursion** of the cone.

Use a lissajous pattern for enhanced effect.




........... Phil

[DrBoom]

"Phil Allison" > wrote in message
>...
> "Bob Cain"
> > Phil Allison wrote:
> > >
> > >>Ok. The false assumption is that the pressure wave created
> > >>by a piston is proportional to its acceleration. It isn't;
> > >>it's proprotional to the piston velocity.
> > >
> > > ** You have evidence ????
> >
> > Better than that, I have a proof by the principle of
> > reciprocity (not at all the same as analogy since it only
> > considers the actual system in question.) If you missed it,
> > I'll be happy to repeat it.
>
>
> ** You have no proof - only your own a mad ideas.

Bob is correct: instantaneous acceleration numbers don't mean much
unless you're doing materials analysis on the cone, suspension, or
motor structure. It doesn't matter if the cone is pulling 100 G's
at some arbitrary point in time (it could have stopped...); it
matters that it moved from point A to point B in X microseconds. It
might not have accelerated _at_all_ during X, but it will still
produce a positive or negative pressure wave.

> Speaker cones reach their greatest velicities at low frequencies
> and large excursions while making the same SPL as at higher
> frequencies with lower velocities.

This is true, but not for the reason you seem to be stating.

The real reason for this is that conventional direct radiator
dynamic loudspeakers lose air coupling efficiency at at about the
frequency whose quarter wavelength is equal to the diameter of the
cone. Excursion has to approximately double for each octave below
this point achieve the same SPL.

-DrBoom

[Chris Hornbeck]

On Sat, 14 Aug 2004 15:24:25 -0700, Bob Cain
> wrote:

>"Doppler distortion" is described as a
>mechanism that occurs at the piston/air interface regardless
>of how that piston gets driven.

Not by me. I'm leaning towards saying that the mechanism
occurs at the linear distance between radiating and receiving
diaphragms. Because it's the linear distance that's modulated.

Chris Hornbeck

[Arny Krueger]

"Chris Hornbeck" > wrote in message

> On Sat, 14 Aug 2004 15:24:25 -0700, Bob Cain
> > wrote:
>
>> "Doppler distortion" is described as a
>> mechanism that occurs at the piston/air interface regardless
>> of how that piston gets driven.
>
> Not by me. I'm leaning towards saying that the mechanism
> occurs at the linear distance between radiating and receiving
> diaphragms. Because it's the linear distance that's modulated.

The mechanism IS the change in linear distance between radiating and
receiving
diaphragms. Because it's the linear distance that's modulated.

[Phil Allison]

"DrBoom"
> "Phil Allison"

> > Speaker cones reach their greatest velocities at low frequencies
> > and large excursions while making the same SPL as at higher
> > frequencies with lower velocities.
>
> This is true, but not for the reason you seem to be stating.
>
> The real reason for this is that conventional direct radiator
> dynamic loudspeakers lose air coupling efficiency at at about the
> frequency whose quarter wavelength is equal to the diameter of the
> cone. Excursion has to approximately double for each octave below
> this point achieve the same SPL.


** So you are claiming constant cone excursion with frequency above some
low frequency is the norm ?? That means all drivers have rising cone
velocity with frequency - doubling every octave. The very highest
velocities would then be found at the top of their operating range. Not so.

The formula " F = m.a " describes the effect of drive force on the voice
coil.

To this, add the formula for the displacement of an accelerating mass: s
= u.t + a.t.t / 2

The squared " t " shows that displacement quadruples when a force operates
for double the time on a given mass.

So, if the drive force (or amplifier current ) remains unchanged but
operates for twice the time before reversing direction ( ie operates at half
the frequency) the cone will move four times as far before it changes
direction.




........... Phil

[Chris Hornbeck]

On Sat, 14 Aug 2004 14:42:57 -0700, Bob Cain
> wrote:

>> If you can't accept the diaphragm's motion as definitive
>> then I'm lost. If you can, then we can move on to the receiving
>> diaphragm.

>Yes, I can. The question is what that motion does to the
>air in front of it.

Suppose the moving diaphragm itself, referenced to the position
of the receiving diaphragm, generated the Doppler effect?
And the diaphragm to air translation were only linear; no
special pleadings in the translation needed?


>LOL! That's the thing. If it exists, it shouldn't take a
>John Baez or an Ed Whitten (prominent mathematical
>physicists) to write it down.

Whenever I've seen Joan Baez, her recitative has leaned more
towards the polemical, but she does let the occasional
trig function slip in.

>The answer to Scott's posed question is simply "It's bigger."
>> The scale makes it significant.
>
>Can't see any basis in physics for that. Seems to be
>another of those intuitive things that can't really be
>justified when push comes to shove. (With all due respect,
>Scott.)

The problem is all in my very, very poor expression of it.
The two moving diaphragms are asymmetrical in their "absolute"
motion, therefore they have some relative motion.

And their relative motion is *all* that's needed for the
Doppler effect.

Maybe what I'm missing is why the audio case must be different
from the case of other waves? Red shift, blue shift, etc.
You're obviously getting at something, but I'm not seeing
it yet.

Chris Hornbeck

[Arny Krueger]

"Chris Hornbeck" > wrote in message


> Maybe what I'm missing is why the audio case must be different
> from the case of other waves? Red shift, blue shift, etc.
> You're obviously getting at something, but I'm not seeing
> it yet.

It's all the same, more or less. Doppler with light, doppler with sound...
At the core is relative motion.

[Chris Hornbeck]

On Sat, 14 Aug 2004 18:04:47 -0700, Bob Cain
> wrote:

>Here is the problem. Since the distance between driver and
>detector is actually the distance from the rest position of
>the driver to the detector, which is true because the driver
>face is riding the wave it creates, there is really no phase
>modulation because there is no distance modulation.

Wow. You can't leave it with just this much. What does
this mean?

Perhaps you would start with: does a single motion modulate
distance? and move on to multiple imbedded motions.

Truely stunned,

Chris Hornbeck

[Bob Cain]

Chris Hornbeck wrote:

> On Sat, 14 Aug 2004 18:04:47 -0700, Bob Cain
> > wrote:
>
>
>>Here is the problem. Since the distance between driver and
>>detector is actually the distance from the rest position of
>>the driver to the detector, which is true because the driver
>>face is riding the wave it creates, there is really no phase
>>modulation because there is no distance modulation.
>
>
> Wow. You can't leave it with just this much. What does
> this mean?

I'll try again. The argument for Doppler distortion
considers the instantaneous distance between reciever and
piston as the distance the sound travels so that as it moves
the distance is modulated and thus the frequency is.

That is incorrect. The reality is that the distance between
receiver and piston, precisely because that piston is riding
the wave, is measured from its rest position and not its
instantaneous position. If the rest position isn't moving
then there is no Doppler shift occuring.

>
> Perhaps you would start with: does a single motion modulate
> distance? and move on to multiple imbedded motions.

Here's another place trouble sets in. There isn't any such
thing as single and multiple embedded moves. That's fuzzy
thinking from the incorrect assumption that in reality
signals are composed of something else. They aren't.

Nonetheless, you should see now that it doesn't matter what
motion the piston engages in while following the signal, it
is the rest position that determines the distance at all
times. Translate it and you have Doppler shift. Simply
oscillate about it and you don't. I think that is because
air only has zero response at DC, but that's off the cuff.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Phil Allison]

"Bob Cain"

> I'll try again. The argument for Doppler distortion
> considers the instantaneous distance between reciever and
> piston as the distance the sound travels so that as it moves
> the distance is modulated and thus the frequency is.
>
> That is incorrect. The reality is that the distance between
> receiver and piston, precisely because that piston is riding
> the wave, is measured from its rest position and not its
> instantaneous position. If the rest position isn't moving
> then there is no Doppler shift occuring.


** But the rest position for the high frequency **IS** moving - at the
low frequency.


>
> Nonetheless, you should see now that it doesn't matter what
> motion the piston engages in while following the signal, it
> is the rest position that determines the distance at all
> times. Translate it and you have Doppler shift. Simply
> oscillate about it and you don't.


** Pure insanity.




.......... Phil

[Chris Hornbeck]

On Sat, 14 Aug 2004 23:25:51 -0700, Bob Cain
> wrote:

>I'll try again. The argument for Doppler distortion
>considers the instantaneous distance between reciever and
>piston as the distance the sound travels so that as it moves
>the distance is modulated and thus the frequency is.
>
>That is incorrect. The reality is that the distance between
>receiver and piston, precisely because that piston is riding
>the wave, is measured from its rest position and not its
>instantaneous position. If the rest position isn't moving
>then there is no Doppler shift occuring.

Very, very cool. I'm beginning to start to begin to get a
grasp on what you're after. You're still wrong, wrong, wrong!
but I may not be smart enough to describe why. Cool beans.

>> Perhaps you would start with: does a single motion modulate
>> distance? and move on to multiple imbedded motions.
>
>Here's another place trouble sets in. There isn't any such
>thing as single and multiple embedded moves. That's fuzzy
>thinking from the incorrect assumption that in reality
>signals are composed of something else. They aren't.

Well, in that light, no classical analysis is possible.
And that's all we're talking about. Admittedly the request
was lame and loaded.

>Nonetheless, you should see now that it doesn't matter what
>motion the piston engages in while following the signal, it
>is the rest position that determines the distance at all
>times. Translate it and you have Doppler shift. Simply
>oscillate about it and you don't. I think that is because
>air only has zero response at DC, but that's off the cuff.

Just when I thought I had it, I fall off the edge of the earth
again.


I still think that this whole avenue is misguided and that the
only real component of receiving diaphragm motion is its
instantaneous differential air pressure, determined in our
model by the air pressure at the source diaphragm.

And I can't see where you're *not* saying that the train
whistle's pitch doesn't change.

In summary: I can't agree with "the piston riding the wave"
or that signals aren't composed of something else. The latter
would also invalidate non-linearity in general. My interpretation
can't be what you meant.

Chris Hornbeck

[Bob Cain]

Chris Hornbeck wrote:

> In summary: I can't agree with "the piston riding the wave"
> or that signals aren't composed of something else. The latter
> would also invalidate non-linearity in general. My interpretation
> can't be what you meant.

How about this: it is the bulk velocity, the flow of air,
at the rest position that propegates out as the velocity
wave. The pressure of the wave follows as usual in phase
with the velocity.

What is the bulk velocity at the rest position as a function
of the velocity of the piston? I think they are simply
proportional.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Chris Hornbeck]

On Sun, 15 Aug 2004 08:29:38 -0700, Bob Cain
> wrote:

>How about this: it is the bulk velocity, the flow of air,
>at the rest position that propegates out as the velocity
>wave. The pressure of the wave follows as usual in phase
>with the velocity.
>
>What is the bulk velocity at the rest position as a function
>of the velocity of the piston? I think they are simply
>proportional.

Sure. And just to be perfectly clear, by bulk velocity you
mean what Beranek calls volume velocity, the time rate of
flow of the medium. And adiabatic conditions.

Chris Hornbeck

[Chris Hornbeck]

On Sat, 14 Aug 2004 23:25:51 -0700, Bob Cain
> wrote:

>Nonetheless, you should see now that it doesn't matter what
>motion the piston engages in while following the signal, it
>is the rest position that determines the distance at all
>times. Translate it and you have Doppler shift. Simply
>oscillate about it and you don't.

By distance here you mean the distance between originating
and receiving pistons?

And by translate you mean to move the rest position of the
originating piston, referenced to the receiving piston?

And by rest position, we mean the no-signal position?

So does the discussion hinge on the uniquely longitudinal
vibration of sound waves?

Can we agree that the distance between originating and
receiving diaphragms is modulated by the signal?

Chris Hornbeck

[Bob Cain]

Chris Hornbeck wrote:

> On Sun, 15 Aug 2004 08:29:38 -0700, Bob Cain
> > wrote:
>
>
>>How about this: it is the bulk velocity, the flow of air,
>>at the rest position that propegates out as the velocity
>>wave. The pressure of the wave follows as usual in phase
>>with the velocity.
>>
>>What is the bulk velocity at the rest position as a function
>>of the velocity of the piston? I think they are simply
>>proportional.
>
>
> Sure. And just to be perfectly clear, by bulk velocity you
> mean what Beranek calls volume velocity, the time rate of
> flow of the medium. And adiabatic conditions.

Yes.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Bob Cain]

Chris Hornbeck wrote:


> Can we agree that the distance between originating and
> receiving diaphragms is modulated by the signal?

No because for the purposes of physics and acoustics, the
reference for measuring the distance is always the rest
position at either end.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

[Chris Hornbeck]

On Sun, 15 Aug 2004 15:25:34 -0700, Bob Cain
> wrote:

>> Can we agree that the distance between originating and
>> receiving diaphragms is modulated by the signal?
>
>No because for the purposes of physics and acoustics, the
>reference for measuring the distance is always the rest
>position at either end.

Are these two statements contradictory?

Well, how about: The distance between originating and
receiving diaphragms is an analog of the signal. With no
signal the reference positions of the diaphragms are
their rest positions and the distance between them is
a constant.

Signal or information is carried by varying the distance
between them and the constant is subtracted out. Conversions
from joltage to air pressure to joltage is symmetrical
and falls out.

Can we agree that this model can define the information
path?

Chris Hornbeck

[Bob Cain]

Chris Hornbeck wrote:

> On Sun, 15 Aug 2004 15:25:34 -0700, Bob Cain
> > wrote:
>
>
>>>Can we agree that the distance between originating and
>>>receiving diaphragms is modulated by the signal?
>>
>>No because for the purposes of physics and acoustics, the
>>reference for measuring the distance is always the rest
>>position at either end.
>
>
> Are these two statements contradictory?

Yes, I'm saying that at no point, at rest in the reference
frame of the rest-position of the driver, will Doppler shift
be observed. In that reference frame, the point of origin
is not modulated by piston motion.

The reason for that I've stated in other responses.


bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein