"Arny Krueger"
"Bob Cain"


That's because this time shift, more specifically the time rate of
change of this time shift, is the cause of Doppler.

Doesn't exist, Arny. Look he

http://www.silcom.com/~aludwig/Physi..._of_sound.html

Tellingly, as deep as the discussion goes, no mention is
made of "Doppler distortion" and if you read it you will see
why such nonsense wouldn't even have been considered.

It also directly supports what I have said recently that
distance from an oscilating piston, for the purposes of the
physics of piston interaction with air is the distance to
the rest position. I must say, that I found this link just
minutes ago, oddly enough looking for links to IR's for
Acoutic Modeler. I fingered it out earlier all by m'self.

Now about that data you posted...

Sorry Bob, but I'm not buying.



** I have a book on geography that no-where mentions that the earth is not
flat.

Will you take that as proof ???




.......... Phil

"Phil Allison" wrote in message

"Arny Krueger"
"Phil Allison"

** So this is what all the Doppler Distortion fuss is about ????

A tiny bit of phase jitter, which at 5 kHz rarely amounts to more
than a few degrees ??

It's not a lot. The most important thing is that its swamped by all
the AM distortion.


** Which, unlike the puny phase jitter, is veeerrrryy audible.

Agreed. With a bullet!

But net it out -we're saying pretty
much the same thing, Phil. The Doppler distortion is there but its
small.

** I found with my test that much of it goes away if you put the
woofer cone at right angles to the mic.

Again, per theory.

I think the guy who brought up Doppler as some kind of a serious
problem did so a few weeks ago. He used Doppler distortion as a
justification for not liking long-excursion woofers. In the end he
admitted that he used 2-way monitors with either 6.5 or 8" woofers,
and no subwoofer. Ironic enough?

** Must just love all that IM.

He even bragged about all of the cone motion, when this little tyke was
driven with LF, I believe he even specifically mentioned 30 Hz.

To recapitulate, the problem with that intuitive view, which
is the whole basis of believing that there is "Doppler
distortion" is that it assumes that the distance from the
driver is the distance from the instantaneous position of
the piston. That's wrong. The distance from the driver,
since it is riding the wave it is creating, is the distance
from its zero or rest position, the position about which it
oscillates. That doesn't change with the nature of the
signal unless there is a DC component.

If the distance from the driver is not changing, there is no
Doppler shift. None of the proposed scenarios which have
the face of the driver oscillating about a rest position
will produce Doppler shift despite intuition.

Sorry, Bob, but I disagree. There is my thought experiment (which I consider
proof). And there is also the claim by an anonymous poster outlining his test
procedure and claiming he measured it.

On Sun, 15 Aug 2004 00:37:44 -0700, Bob Cain
wrote:

If the distance from the driver is not changing, there is no
Doppler shift.


I wrote:

The distance from which part of the driver? The frame? The cone?
Something else?

The rest position, the one it will settle to when the
driving signal is removed. If the driving signal contains a
DC component, and the piston is not restrained by a
compliance, then and only then will Doppler shift occurs.
Hard to swallow, I know but it is the truth.

Okay, Bob, I'm going to add a DC component, but I'm not going to
tell you that this DC component is really a millihertz-frequency sine
wave. How will you know the difference? Just what IS the difference
over a time period of one second?

Bob

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

Ben Bradley wrote:


Okay, Bob, I'm going to add a DC component, but I'm not going to
tell you that this DC component is really a millihertz-frequency sine
wave. How will you know the difference? Just what IS the difference
over a time period of one second?

Enough. :-)


Bob
--

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

A. Einstein

Arny Krueger wrote:


Sorry Bob, but I'm not buying.

How about this, then:

1) It is the bulk velocity, the flow of air, at the rest
position that propegates out as the velocity wave.

2) The bulk velocity at the rest position is the same as the
surface velocity of the piston.


Bob
--

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

A. Einstein

"Phil Allison" wrote in message

"Arny Krueger"
"Bob Cain"


That's because this time shift, more specifically the time rate of
change of this time shift, is the cause of Doppler.

Doesn't exist, Arny. Look he

http://www.silcom.com/~aludwig/Physi..._of_sound.html

Tellingly, as deep as the discussion goes, no mention is
made of "Doppler distortion" and if you read it you will see
why such nonsense wouldn't even have been considered.

It also directly supports what I have said recently that
distance from an oscilating piston, for the purposes of the
physics of piston interaction with air is the distance to
the rest position. I must say, that I found this link just
minutes ago, oddly enough looking for links to IR's for
Acoutic Modeler. I fingered it out earlier all by m'self.

Now about that data you posted...

Sorry Bob, but I'm not buying.

** I have a book on geography that no-where mentions that the earth
is not flat.

Will you take that as proof ???

I think you misunderstood my intent. I have no problems with Art Ludwig's
recital of the laws of physics, I have problems with Bob's interpretation of
them.

"Arny Krueger"
"Phil Allison"

** I have a book on geography that no-where mentions that the earth
is not flat.

Will you take that as proof ???

I think you misunderstood my intent.


** I think you missed the irony.





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

William Sommerwerck wrote:

To recapitulate, the problem with that intuitive view, which
is the whole basis of believing that there is "Doppler
distortion" is that it assumes that the distance from the
driver is the distance from the instantaneous position of
the piston. That's wrong. The distance from the driver,
since it is riding the wave it is creating, is the distance
from its zero or rest position, the position about which it
oscillates. That doesn't change with the nature of the
signal unless there is a DC component.


If the distance from the driver is not changing, there is no
Doppler shift. None of the proposed scenarios which have
the face of the driver oscillating about a rest position
will produce Doppler shift despite intuition.


Sorry, Bob, but I disagree.

Can you be more specific. I don't mean by offering another
scenario which I must find specific disagreement with but
doing it yourself with what I've offered. What part of it
is wrong?


Bob
--

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

A. Einstein

Bob Cain wrote:



Arny Krueger wrote:


Sorry Bob, but I'm not buying.


How about this, then:

1) It is the bulk velocity, the flow of air, at the rest position that
propegates out as the velocity wave.

2) The bulk velocity at the rest position is the same as the surface
velocity of the piston.

And, finally:

3) In the frame of reference of the rest position of the
piston, no Doppler shift can be observed.


Bob
--

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

A. Einstein

If the distance from the driver is not changing, there is no
Doppler shift. None of the proposed scenarios which have
the face of the driver oscillating about a rest position
will produce Doppler shift despite intuition.


Sorry, Bob, but I disagree.

Can you be more specific. I don't mean by offering another
scenario which I must find specific disagreement with but
doing it yourself with what I've offered. What part of it
is wrong?

Consider the Principle of Superposition. QED.

"Ben Bradley" wrote in message
...
On Sun, 15 Aug 2004 00:37:44 -0700, Bob Cain
wrote:

If the distance from the driver is not changing, there is no
Doppler shift.


I wrote:

The distance from which part of the driver? The frame? The cone?
Something else?

The rest position, the one it will settle to when the
driving signal is removed. If the driving signal contains a
DC component, and the piston is not restrained by a
compliance, then and only then will Doppler shift occurs.
Hard to swallow, I know but it is the truth.

Okay, Bob, I'm going to add a DC component, but I'm not going to
tell you that this DC component is really a millihertz-frequency sine
wave. How will you know the difference? Just what IS the difference
over a time period of one second?

Here's a simple way out of this one, with a very slow oscillation of a
varying DC component, the cone won't be moving at a high enough velocity to
generate doppler distortion, even if it is moving two or more inches p-p.
Forget millihertz, even one hertz at 2 inches displacement is going to be a
peak velocity of less than one half foot per second. At that velocity, it
simply doesn't have time to dopple!:-)

In article ,
"Phil Allison" wrote:

"Arny Krueger"
"Phil Allison"
"Jim Carr"

With that said, help me out here. I can't get myself away from the
assumption that since a speaker diaphragm has a throw of a certain
distance, then the waves started by the diaphragm may be started
from any point in that throw. As such two waves which are created a
certain time apart may end up travelling different distances to reach
my stationary ear, thus a Doppler shift.


** A time delay or advance is just that - it is not Doppler. Any
such delay or advance depends solely on the position of the cone -
not its *velocity*. If a cone is displaced by 10mm, that will
introduce a time error of 29 uS or a phase shift of 50 degrees at 5
kHz.

Any attempt to measure Doppler frequency shifts must allow for this
- most have not.

That's because this time shift, more specifically the time rate of change
of
this time shift, is the cause of Doppler.



** So this is what all the Doppler Distortion fuss is about ????

A tiny bit of phase jitter, which at 5 kHz rarely amounts to more than a
few degrees ??


I was looking at it on my scope yesterday:


1. A 5 inch woofer, in box, driven by an amp fed from with two sine wave
generators with outputs summed.

2. A condenser mic feeding a pre-amp and followed by a 12 dB/oct HPF at
2 kHz thence to the scope.

3. The high frequency generator output is also linked to the scope which
operates in X-Y mode.

4. Park mic in front of woofer fed with a circa 5000 Hz sine wave at
about 10 watts. ( I used ear muffs)

5. Adjust scope and exact mic position to get a straight, diagonal line
traced on the scope screen - note that adjusting the 5000 Hz amplitude
affects the angle of the diagonal line only (ie makes it easy to visually
distinguish amplitude modulation ).

6. Turn up low frequency generator, set to say 40 Hz, and watch the line
open out to form a narrow ellipse indicating that the phase is changing as
the cone moves closer and further away from the mic.

7. Sweep low frequency generator up and down and note that cone excursion
alone controls the size of the ellipse - it never opens out more than
about 15 degrees for a linear cone excursion of 3 mm.

8. Try hard to imagine that this is the notorious, evil, Doppler
distortion before your eyes.

A dynamic loudspeaker is a mechanical system operated above resonance.
That means that the instantaneous position of the cone is *not*
represented by the voltage across the voice coil at that instant -- in
other words, there is a phase shift between the driving voltage and the
driven cone.

Compared to the displacement of the cone when driven by a DC voltage of
a certain amplitude, at cone resonance, the phase shift is 90 degrees;
well above that frequency it approaches 180 degrees.

To visualize how the driving force and the cone excursion are not in
phase, experiment with a weight on the end of a rubber band, the weight
heavy enough to cause the band to be significantly stretched. Put
several bands in series to make it easier -- say 18" or so long when
stretched.

Hold the upper end of the string of bands in your hand, and move your
hand up and down very slowly. The weight follows along, in phase. This
is below resonance.

Now move your hand up and down fast. The weight goes up when your hand
goes down. This is well above resonance.

If you are careful, you can find resonance, and note that the motion of
the weight moves in quadrature to the position of your hand.

Notice also that when above resonance, the peak-to-peak displacement of
the weight goes down as the driving frequency goes up, if you hold the
excursion of your hand constant. This is exactly the way that a
loudspeaker maintains constant SPL over frequency when operated in its
"passband". It's automatic, an inevitable result of a mechanical system
being operated above resonance.

Could this explain the phase shift you are seeing? What happens if,
instead of changing cone excursion by changing the frequency, you keep
the frequency constant and adjust the amplitude?

Isaac

"Isaac Wingfield"
"Phil Allison"

Could this explain the phase shift you are seeing?

** No.

Static phase shift was simply adjusted out by positioning the mic at a spot
where the drive voltage and sound pressure were in phase as is evidenced by
the lissajous pattern becoming a line - only the additional shift from
the low frequency cone movement was being observed.


What happens if, instead of changing cone excursion by changing the
frequency, you keep
the frequency constant and adjust the amplitude?


** The phase shift is proportional to cone displacement - as I already
stated.

Cone velocity did not alter the peak amplitude of the oscillating
phase shift.




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

Porky wrote:

At that velocity, it
simply doesn't have time to dopple!:-)

That's cute. Wrong, but nonetheless cute. :-)


Bob
--

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

A. Einstein

"Bob Cain" wrote in message
...


Porky wrote:

At that velocity, it
simply doesn't have time to dopple!:-)

That's cute. Wrong, but nonetheless cute. :-)


True, but who's going to hear doppler shift at that level, even if it does
exist?:-)
I think in typical speaker systems, doppler distortion is among the lesser
of our distortion worries, even assuming that it does exist. I see valid
points on both sides of the discussion, but I just don't think it's that big
a priority until other forms of more severe distortion are conquered. I
don't think anyone here thinks that Doppler is the worst form of distortion
in high quality studio monitors, or even in high quality home speakers at
the current state of the art of speaker design.

I finally figured out why I can't sing on pitch, it's doppler distortion!
When I try to sing, subsonic millihertz vibrations in my vocal chords cause
the audible notes to be shifted in pitch, and since my eardrums are subject
to the same millihertz vibrations, they are in motional phase with my vocal
chords, the result being that I don't hear the variations in pitch until I
play back the recording. Yeah, that's the ticket, I'll blame it all on
Doppler! *LOL*
Thanks guys, for inspiring such a novel, rational sounding excuse for why
I can't sing!:-)

Porky wrote:

True, but who's going to hear doppler shift at that level, even if it does
exist?:-)

To me it doesn't matter whether we can hear it or not. As
of now there is no predictive theory that yields
quantitative results we could test with experiment anyway.
I want to know whether or not it is a real phenomenon at all.

One of the reasons this issue is of importance to me is that
on the ProAudio mailing list they argue endlessly about
effects that are so small in predicted physical consequence
that they would be swamped by even a pretty darned small
"Doppler distortion" if it existed. If it really does exist
then a whole lot of what they discuss and argue about in
other areas could well be irrelevant. This is not an
unimportant issue to have settled.


Bob
--

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

A. Einstein

Porky wrote:

I finally figured out why I can't sing on pitch, it's doppler distortion!
When I try to sing, subsonic millihertz vibrations in my vocal chords cause
the audible notes to be shifted in pitch, and since my eardrums are subject
to the same millihertz vibrations, they are in motional phase with my vocal
chords, the result being that I don't hear the variations in pitch until I
play back the recording. Yeah, that's the ticket, I'll blame it all on
Doppler! *LOL*
Thanks guys, for inspiring such a novel, rational sounding excuse for why
I can't sing!:-)

That's a truly brilliant rationalization, Porky. Just
remember that anything that must be rationalized is highly
unlikely to be rational. :-)


Bob
--

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

A. Einstein

"Bob Cain" wrote in message

Porky wrote:

True, but who's going to hear doppler shift at that level, even if
it does exist?:-)

To me it doesn't matter whether we can hear it or not. As
of now there is no predictive theory that yields
quantitative results we could test with experiment anyway.
I want to know whether or not it is a real phenomenon at all.

How are you doing with the 60KB or so of AES paper references that I posted
in RAP?

;-)

"Bob Cain" wrote in message

Bob Cain wrote:



Arny Krueger wrote:


Sorry Bob, but I'm not buying.


How about this, then:

1) It is the bulk velocity, the flow of air, at the rest position
that propagates out as the velocity wave.

Frankly, over my head.

2) The bulk velocity at the rest position is the same as the surface
velocity of the piston.

Frankly, over my head.

And, finally:

3) In the frame of reference of the rest position of the
piston, no Doppler shift can be observed.

That seems wrong, because the following is right:

In the frame of reference of the piston, no Doppler shift can be observed.

That's the listener riding the same train as the whistle.

"Bob Cain" wrote in message
...


Porky wrote:

I finally figured out why I can't sing on pitch, it's doppler
distortion!
When I try to sing, subsonic millihertz vibrations in my vocal chords
cause
the audible notes to be shifted in pitch, and since my eardrums are
subject
to the same millihertz vibrations, they are in motional phase with my
vocal
chords, the result being that I don't hear the variations in pitch until
I
play back the recording. Yeah, that's the ticket, I'll blame it all on
Doppler! *LOL*
Thanks guys, for inspiring such a novel, rational sounding excuse for
why
I can't sing!:-)

That's a truly brilliant rationalization, Porky. Just
remember that anything that must be rationalized is highly
unlikely to be rational. :-)


I agree with that, and I wonder how much else in this discussion comes
from rationalization.
It occurs to me that anything so hard to test and measure, even to the
point of proving that it exists at all, is so likely to be absolutely
inconsequential in its effects in the real world that it doesn't really rate
more than a note in passing, especially when real world speakers have so
many other flaws that can be quantized, measured, and even heard by
virtually anyone who bothers to listen and compare.
Virtually all involved in this discussion have made good points that seem
both logical and valid, but as I see it, everyone is basing their logic on
one or another assumption. If one assumes that complex music can actually be
broken down into a group of pure tones and a loudspeaker works by
reproducing all those tones individually, then yes, Doppler distortion
should exist in the output. Conversely, if one assumes that the complex
music waveform is reproduced as a gestalt by the loudspeaker, then no,
Doppler distortion is not likely be introduced by the speaker. It would seem
that the physics allow for both positions, as well as any combination of the
two, so I don't think the discussion is likely to be settled here, unless
someone can come up with a way to test for Doppler distortion in a
loudspeaker that everyone will agree is a valid test, and let those who have
access to the appropriate test equipment run the test(s) and publish their
results to these groups.
So, anyone want to describe a test procedure that can be done with
equipment that at least some of us are likely to have access to, and see if
everyone will agree that it's valid and that it will measure Doppler
distortion while excluding any other form of distortion that could be
mistaken for Doppler?

"Arny Krueger" wrote in message
news
"Bob Cain" wrote in message

Bob Cain wrote:



Arny Krueger wrote:


Sorry Bob, but I'm not buying.


How about this, then:

1) It is the bulk velocity, the flow of air, at the rest position
that propagates out as the velocity wave.

Frankly, over my head.

2) The bulk velocity at the rest position is the same as the surface
velocity of the piston.

Frankly, over my head.

And, finally:

3) In the frame of reference of the rest position of the
piston, no Doppler shift can be observed.

That seems wrong, because the following is right:

In the frame of reference of the piston, no Doppler shift can be
observed.

That's the listener riding the same train as the whistle.


It seems to me that the train/whistle anology is not a valid one for this
purpose, because the train's motion and the whistle's sound are not being
reproduced by the same source, as happens in a loudspeaker producing a
complex waveform.
If you make a recording of the train approaching and receeding from your
listening position and play it back, you will hear exactly the same Doppler
shift you heard when the train went by, and this can be confirmed by
measurement. Conversely, if you make a recording of the whistle from the
train and play it back on a speaker moving down the tracks at the same
velocity as the train, you will hear the same doppler shift you heard from
the passing train, even though there is no shift in the actual recording.
The above logic actually has little to do with Doppler distortion in a
speaker, but the fact remains that the train/whistle in not a valid anology!
Making the assumption that a speaker produces Doppler shift because a
whistle on a moving train does is a rationalization not based on the actual
physical facts. Even moving the whistle back and forth in approximation of a
moving speaker cone is not a valid anology, because the whistle's back and
forth motion is not generated by the sound coming from the whistle, as it
would be in a speaker reproducing a complex waveform. You're actually
dealing with two separate sources producing separate waveforms. Mounting the
whistle on the speaker cone still won't be a valid anology because the
waveforms are not being reproduced by the same mechanism, two separate
sources again.
The only valid anology for what happens with a speaker reproducing a
complex waveform would be some other single entity that is capable of
reproducing the same complex waveform. Any suggestions?

"Porky"

"Arny Krueger"

That's the listener riding the same train as the whistle.


It seems to me that the train/whistle anology is not a valid one for
this
purpose, because the train's motion and the whistle's sound are not being
reproduced by the same source, as happens in a loudspeaker producing a
complex waveform.


** How so ? The whiste is mounted on the train.


If you make a recording of the train approaching and receeding from your
listening position and play it back, you will hear exactly the same
Doppler
shift you heard when the train went by, and this can be confirmed by
measurement. Conversely, if you make a recording of the whistle from the
train and play it back on a speaker moving down the tracks at the same
velocity as the train, you will hear the same doppler shift you heard from
the passing train, even though there is no shift in the actual recording.


** No kidding.


The above logic actually has little to do with Doppler distortion in a
speaker, but the fact remains that the train/whistle in not a valid
anology!


** I saw no relevant facts go by - must have just whizzed past on an
express train .......


Making the assumption that a speaker produces Doppler shift because a
whistle on a moving train does is a rationalization not based on the
actual
physical facts.


** You rationalisations are far more extensive and non logical.



Even moving the whistle back and forth in approximation of a
moving speaker cone is not a valid anology, because the whistle's back and
forth motion is not generated by the sound coming from the whistle, as it
would be in a speaker reproducing a complex waveform.


** Huh ? Since when is a cone's motion *produced* by sound ???



You're actually dealing with two separate sources producing separate
waveforms.
Mounting the whistle on the speaker cone still won't be a valid anology
because the
waveforms are not being reproduced by the same mechanism, two separate
sources again.

The only valid anology for what happens with a speaker reproducing a
complex waveform would be some other single entity that is capable of
reproducing the same complex waveform. Any suggestions?


** Lay off the weed.




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

"Phil Allison" wrote in message
...

"Porky"

"Arny Krueger"

That's the listener riding the same train as the whistle.


It seems to me that the train/whistle anology is not a valid one for
this
purpose, because the train's motion and the whistle's sound are not
being
reproduced by the same source, as happens in a loudspeaker producing a
complex waveform.


** How so ? The whiste is mounted on the train.


If you make a recording of the train approaching and receeding from your
listening position and play it back, you will hear exactly the same
Doppler
shift you heard when the train went by, and this can be confirmed by
measurement. Conversely, if you make a recording of the whistle from the
train and play it back on a speaker moving down the tracks at the same
velocity as the train, you will hear the same doppler shift you heard
from
the passing train, even though there is no shift in the actual
recording.


** No kidding.


The above logic actually has little to do with Doppler distortion in a
speaker, but the fact remains that the train/whistle in not a valid
anology!


** I saw no relevant facts go by - must have just whizzed past on an
express train .......


Making the assumption that a speaker produces Doppler shift because a
whistle on a moving train does is a rationalization not based on the
actual
physical facts.


** You rationalisations are far more extensive and non logical.



Even moving the whistle back and forth in approximation of a
moving speaker cone is not a valid anology, because the whistle's back
and
forth motion is not generated by the sound coming from the whistle, as
it
would be in a speaker reproducing a complex waveform.


** Huh ? Since when is a cone's motion *produced* by sound ???



You're actually dealing with two separate sources producing separate
waveforms.
Mounting the whistle on the speaker cone still won't be a valid anology
because the
waveforms are not being reproduced by the same mechanism, two separate
sources again.

The only valid anology for what happens with a speaker reproducing a
complex waveform would be some other single entity that is capable of
reproducing the same complex waveform. Any suggestions?


** Lay off the weed.

The sound produced by the speaker happens because the speaker is driven
by a single complex waveform, thus there is a single source for the sound.
The sound that comes from a train whistle is generated by the whistle, and
the motion imparted to the whistle comes from the train's motion, two
separate sources. If you move the whistle back and forth in a manner
approximating that of a speaker cone, you still have two sources, the
whistle's sound and the mechanical vibration of the whistle, if you mount
the whistle on the speaker cone, you have two sources, that driving the cone
and that coming from the whistle. None of those approximates in any way, or
is a valid anology for a loudspeaker producing a complex waveform that comes
from only one source, the complex electrical waveform driving the speaker
motor. All the other anologies have two sources, one for the low frequency
motion and one for the high frequency sound, NOT a valid anology for what
happens when a speaker reproduced a complex waveform. If you don't get that,
then perhaps it is you who should "lay off the weed". You aren't going to
get it until you can differentiate that which comes from two or more
separate simple driving sources and that which comes from a single complex
driving source
BTW, I never said anything about a cone's motion being prodiuced by sound.
I said "a speaker reproducing a complex waveform".

"Porky"

The sound produced by the speaker happens because the speaker is driven
by a single complex waveform, thus there is a single source for the sound.
The sound that comes from a train whistle is generated by the whistle, and
the motion imparted to the whistle comes from the train's motion, two
separate sources.


** WRONG !!!

There is only one source of sound in both cases.

Case 1 = the cone.

Case 2 = the whistle.



If you move the whistle back and forth in a manner
approximating that of a speaker cone, you still have two sources, the
whistle's sound and the mechanical vibration of the whistle, if you mount
the whistle on the speaker cone, you have two sources, that driving the
cone
and that coming from the whistle.


** I told you to lay off that damn weed !!


None of those approximates in any way, or
is a valid anology for a loudspeaker producing a complex waveform that
comes
from only one source, the complex electrical waveform driving the speaker
motor.


** The SOURCE source of any sound is the vibrating object or air column.


All the other anologies have two sources, one for the low frequency
motion and one for the high frequency sound,


** Simply not relevant.


NOT a valid anology for what
happens when a speaker reproduced a complex waveform. If you don't get
that,
then perhaps it is you who should "lay off the weed".


** There is nothing rational anywhere in your posts to get.


You aren't going to
get it until you can differentiate that which comes from two or more
separate simple driving sources and that which comes from a single complex
driving source


** Totally false distinction.

It exists only in the words.


BTW, I never said anything about a cone's motion being prodiuced by
sound.
I said "a speaker reproducing a complex waveform".


** Quote:

" Even moving the whistle back and forth in approximation of a
moving speaker cone is not a valid anology, because the whistle's back
and forth motion is not generated by the sound coming from the whistle, as
it would be in a speaker reproducing a complex waveform. "


** Yes you did, then deceitfully snipped it.

Bet the weed made you do that......




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

"Porky" wrote in message

"Arny Krueger" wrote in message
news
"Bob Cain" wrote in message

Bob Cain wrote:



Arny Krueger wrote:


Sorry Bob, but I'm not buying.


How about this, then:

1) It is the bulk velocity, the flow of air, at the rest position
that propagates out as the velocity wave.

Frankly, over my head.

2) The bulk velocity at the rest position is the same as the
surface velocity of the piston.

Frankly, over my head.

And, finally:

3) In the frame of reference of the rest position of the
piston, no Doppler shift can be observed.

That seems wrong, because the following is right:

In the frame of reference of the piston, no Doppler shift can be
observed.

That's the listener riding the same train as the whistle.


It seems to me that the train/whistle anology is not a valid one for
this purpose, because the train's motion and the whistle's sound are
not being reproduced by the same source, as happens in a loudspeaker
producing a complex waveform.

It's just a matter of scale. The world is the equivalent of the chassis of
the speaker. The effective diaphragm of the whistel is the woofer cone.

If you make a recording of the train approaching and receeding from
your listening position and play it back, you will hear exactly the
same Doppler shift you heard when the train went by, and this can be
confirmed by measurement.

And, if the train travels in a really large sine wave, it's a lot like a
speaker.

Conversely, if you make a recording of the
whistle from the train and play it back on a speaker moving down the
tracks at the same velocity as the train, you will hear the same
doppler shift you heard from the passing train, even though there is
no shift in the actual recording.

Agreed..

The above logic actually has
little to do with Doppler distortion in a speaker, but the fact
remains that the train/whistle in not a valid anology!

Have it your way, if that's what you want. I'm not buying that there is a
substantial difference.

Making the
assumption that a speaker produces Doppler shift because a whistle on
a moving train does is a rationalization not based on the actual
physical facts.

False.

Even moving the whistle back and forth in
approximation of a moving speaker cone is not a valid anology,
because the whistle's back and forth motion is not generated by the
sound coming from the whistle, as it would be in a speaker
reproducing a complex waveform.

Let's presume that the whistle is actually a mechanical horn with a
diaphragm which of course undergoes the identical same Doppler shift as an
air horn or steam whistle. The diaphragm of this mechanical train horn
follows a similar path, different only in scale, from a woofer cone.

You're actually dealing with two
separate sources producing separate waveforms.

Doesn't matter because the diaphragm that actually makes the sound follows a
similar path.

Mounting the whistle
on the speaker cone still won't be a valid anology because the
waveforms are not being reproduced by the same mechanism, two
separate sources again.

This turns out to be an irrelevant distinction. What matters is the path of
the diaphragm, or its moral equivalent.

The only valid anology for what happens with
a speaker reproducing a complex waveform would be some other single
entity that is capable of reproducing the same complex waveform. Any
suggestions?

A train, car or a boat.

The sound produced by the speaker happens because the speaker is driven
None of those approximates in any way, or
is a valid anology for a loudspeaker producing a complex waveform that comes
from only one source, the complex electrical waveform driving the speaker
motor. All the other anologies have two sources, one for the low frequency
motion and one for the high frequency sound, NOT a valid anology for what
happens when a speaker reproduced a complex waveform.

What if we take this to the extremes with a thought experiment:

Picture the largest loudspeaker in the universe sitting outside
somewhere. It's so big that it has a maximal excursion of several
feet. Now picture a very low bass signal played on that speaker at
almost maximal volume. The speaker cone is vibrating
in-out-in-out-in-out.

Now add to that signal a small, high pitched, low amplitude waveform.
The two waveforms are added together so that it seems like the higher
pitched wave is "riding on top of" the bass wave. As far as our
super-excursion speaker is concerned, the location that's generating
the high pitched sound is moving forward and backward several feet.

If you still don't believe that this scenario validates the
train-whistle analogy, why not make the bass waveform move at the
speed of, oh say a train, and have the high pitched signal on top of
it be, oh say the sound of a whistle.

The scenario described in this thought experiment would *certainly*
produce doppler shift in the higher signals. If you made the bass
carrier sound low enough frequency and loud enough, you would even be
able to hear the weeeooohhweeeoooh modulation of the higher frequency
as the source of that sound (the surface of the speaker cone) is
moving towards and away from you. It follows reasonably that this also
happens with regular speakers, but to a lesser extent.

The question of whether it's a relevant, measurable, or hearable
distortion is a separate issue from whether it physically exists.

Forgive me if this has already been discussed to this point, I didn't
have time to read the entire thread.

Ken

"PenguiN"

What if we take this to the extremes with a thought experiment:

Picture the largest loudspeaker in the universe sitting outside
somewhere. It's so big that it has a maximal excursion of several
feet. Now picture a very low bass signal played on that speaker at
almost maximal volume. The speaker cone is vibrating
in-out-in-out-in-out.

Now add to that signal a small, high pitched, low amplitude waveform.
The two waveforms are added together so that it seems like the higher
pitched wave is "riding on top of" the bass wave. As far as our
super-excursion speaker is concerned, the location that's generating
the high pitched sound is moving forward and backward several feet.

If you still don't believe that this scenario validates the
train-whistle analogy, why not make the bass waveform move at the
speed of, oh say a train, and have the high pitched signal on top of
it be, oh say the sound of a whistle.

The scenario described in this thought experiment would *certainly*
produce doppler shift in the higher signals. If you made the bass
carrier sound low enough frequency and loud enough, you would even be
able to hear the weeeooohhweeeoooh modulation of the higher frequency
as the source of that sound (the surface of the speaker cone) is
moving towards and away from you. It follows reasonably that this also
happens with regular speakers, but to a lesser extent.

The question of whether it's a relevant, measurable, or hearable
distortion is a separate issue from whether it physically exists.

Forgive me if this has already been discussed to this point, I didn't
have time to read the entire thread.

Ken



** I reckon Ken must be an ambulatoy gum chewer.



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

ruffrecords writes:

PenguiN wrote:
The sound produced by the speaker happens because the speaker is driven
None of those approximates in any way, or
is a valid anology for a loudspeaker producing a complex waveform that comes
from only one source, the complex electrical waveform driving the speaker
motor. All the other anologies have two sources, one for the low frequency
motion and one for the high frequency sound, NOT a valid anology for what
happens when a speaker reproduced a complex waveform.

What if we take this to the extremes with a thought experiment:

Picture the largest loudspeaker in the universe sitting outside

somewhere. It's so big that it has a maximal excursion of several
feet. Now picture a very low bass signal played on that speaker at
almost maximal volume. The speaker cone is vibrating
in-out-in-out-in-out.
Now add to that signal a small, high pitched, low amplitude waveform.

The two waveforms are added together so that it seems like the higher
pitched wave is "riding on top of" the bass wave.


What gets added are the instantaneous pressures. The air pressure
produced is exactly the same as two separate speakers at the two
frequencies. There is no such thing as doppler distortion.

Consider this gedanken: Place a 4-inch speaker on the cone of a 14-foot
speaker. Now, the two speakers are fed different signals. Is there
Doppler? Yes. Use the one 14-foot speaker for both frequencies. Is there
Doppler? Left as an exercise for the student.

Granted, there will be differences, but the lack of doppler will not
be one of them. One of them will be the dispersion characterstics of
the high-frequency signal.

The difference between receiving two such summed signals electrically
versus acoustically is that one has the physical phenomenom of the
propagation of sound through the air in one case and not in the other.
Similarly, an electronic receiver may have other types of non-linear
distortion (e.g., clipping) depending on the circuit and parameters
that an acoustic receiver would not have. The two do not necessarily
have to agree with one another - there are different physical processes
that occur in each.

Get out a physics book and read about Doppler. The explanation of
how the observed wavelength changes when there is a relative velocity
between the source and observer should make you a believer that this
is precisely the scene in a speaker reproducing two frequencies.
--
Randy Yates
Sony Ericsson Mobile Communications
Research Triangle Park, NC, USA
, 919-472-1124

"ruffrecords" wrote in message


PenguiN wrote:

As far as our
super-excursion speaker is concerned, the location that's generating
the high pitched sound is moving forward and backward several feet.

No it isn't. This is the flaw in all the doppler distortion
arguments.

If all the explanations for Doppler distortion are wrong, where does all of
the FM we measure come from? Why does it correlate well with the *incorrect*
theoretical predictions?

PenguiN wrote:
The sound produced by the speaker happens because the speaker is driven
None of those approximates in any way, or
is a valid anology for a loudspeaker producing a complex waveform that comes
from only one source, the complex electrical waveform driving the speaker
motor. All the other anologies have two sources, one for the low frequency
motion and one for the high frequency sound, NOT a valid anology for what
happens when a speaker reproduced a complex waveform.


What if we take this to the extremes with a thought experiment:

Picture the largest loudspeaker in the universe sitting outside
somewhere. It's so big that it has a maximal excursion of several
feet. Now picture a very low bass signal played on that speaker at
almost maximal volume. The speaker cone is vibrating
in-out-in-out-in-out.

Now add to that signal a small, high pitched, low amplitude waveform.
The two waveforms are added together so that it seems like the higher
pitched wave is "riding on top of" the bass wave.

What gets added are the instantaneous pressures. The air pressure
produced is exactly the same as two separate speakers at the two
frequencies. There is no such thing as doppler distortion.

Ian


As far as our
super-excursion speaker is concerned, the location that's generating
the high pitched sound is moving forward and backward several feet.

No it isn't. This is the flaw in all the doppler distortion arguments.

Ian

In alt.music.home-studio,rec.audio.tech,rec.audio.pro,
(PenguiN) wrote:

The sound produced by the speaker happens because the speaker is driven
None of those approximates in any way, or
is a valid anology for a loudspeaker producing a complex waveform that comes
from only one source, the complex electrical waveform driving the speaker
motor. All the other anologies have two sources, one for the low frequency
motion and one for the high frequency sound, NOT a valid anology for what
happens when a speaker reproduced a complex waveform.

What if we take this to the extremes with a thought experiment:

Picture the largest loudspeaker in the universe sitting outside
somewhere. It's so big that it has a maximal excursion of several
feet. Now picture a very low bass signal played on that speaker at
almost maximal volume. The speaker cone is vibrating
in-out-in-out-in-out.

Now add to that signal a small, high pitched, low amplitude waveform.
The two waveforms are added together so that it seems like the higher
pitched wave is "riding on top of" the bass wave. As far as our
super-excursion speaker is concerned, the location that's generating
the high pitched sound is moving forward and backward several feet.

If you still don't believe that this scenario validates the
train-whistle analogy, why not make the bass waveform move at the
speed of, oh say a train, and have the high pitched signal on top of
it be, oh say the sound of a whistle.

The scenario described in this thought experiment would *certainly*
produce doppler shift in the higher signals. If you made the bass
carrier sound low enough frequency and loud enough, you would even be
able to hear the weeeooohhweeeoooh modulation of the higher frequency
as the source of that sound (the surface of the speaker cone) is
moving towards and away from you. It follows reasonably that this also
happens with regular speakers, but to a lesser extent.

The question of whether it's a relevant, measurable, or hearable
distortion is a separate issue from whether it physically exists.

Forgive me if this has already been discussed to this point, I didn't
have time to read the entire thread.

I made what I considered to be a similar 'extreme' post, but your
woofer cone moves an order or two of magnitide greater distance than
mine does. So I commend your post, it needed to be said.

As far as not having time to read the whole thread, I've been
participating, so it's a sad commentary on where I'm spending my time.

Someone should have just said at the start "Bob Cain (and a few
others here) is in denial about the existence of Doppler effect in
speakers" and I wouldn't have tried so hard...

Ken

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

I haven't read this stuff but it might be of interest to people
involved in this thread.


The Audibility of Doppler Distortion in Loudspeakers
Author(s): Allison, Roy; Villchur, Edgar
Publication: Preprint 1769; Convention 69; May 1981


The Audibility of Doppler Distortion in Loudspeakers
Author(s): Allison, Roy; Villchur, Edgar
Publication: Preprint 1844; Convention 70; October 1981

Loudspeaker Distortion with Low-Frequency Signals
Author(s): Harwood, H.D.
Publication: Volume 20 Number 9 pp. 718·728; November 1972


On the Magnitude and Audibility of FM Distortion in Loudspeakers
Author(s): Allison, Roy; Villchur, Edgar
Publication: Volume 30 Number 10 pp. 694·700; October 1982

Simulation and Investigation of Doppler Distortion
Author(s): Fryer, P. A.
Publication: Preprint 1197; Convention 56; March 1977


Doppler Distortion in Loudspeakers
Author(s): Moir, James
Publication: Preprint 925; Convention 46; September 1973

On the Doppler Distortion in Loudspeakers
Author(s): Braun, S.
Publication: Volume 21 Number 3 pp. 185·187; April 1973

This is a really great discussion.

The original poster asked for suggestions for more experiments. I
suggest connecting the spectrum analyzer directly to the speaker,
don't use a mic. This will verify that this distortion is not caused
in the electronics. I doubt that it would be, but it would be nice to
verify.

The sidebands do look like FM. They also look like IM which I presume
you are calling AM. Note that both FM and AM produce symmetrical
sidebands. However when both AM and FM are present together, the
combination usually produces asymmetrical sidebands. This is because
the AM and FM sidebands have different phases above and below the
carrier. Since the sidebands in your experiment look pretty
symmetrical I would say that if AM and FM are present together, they
are not close to equal. If they were close to equal, the sidebands
would be very asymmetrical.

So how do we tell if the sidebands are FM or AM?

Suggestion. Send the signal through a 4 kHz BPF that is wide enough
to pass the sidebands but not wide enough to pass the 50 Hz or it's
harmonics. You should then be able to analyze this BP signal to see
if it is AM or FM. If it is AM, the envelope will vary at 50 Hz. If
it is FM, the envelope will be constant.

Here is the interesting part in my mind...
Regarding how this sounds, it really doesn't matter if the sidebands
are produced by AM or FM (doppler). The ear works like an FFT
analyzer. If the sideband structure looks the same, then it will
sound the same. Doppler is a non-linear process just like FM and IM
that produces new sidebands.

Mark

On Sun, 15 Aug 2004 22:56:47 -0700, Bob Cain
wrote:



Porky wrote:

At that velocity, it
simply doesn't have time to dopple!:-)

That's cute. Wrong, but nonetheless cute. :-)

It WILL cause a phase shift, and I have no doubt you can set this
up and see a practical demonstration of this on an oscilloscope, and
phase shift, no matter how slow, IS equivalent to a frequency change.

It dopples, just as surely at the Earth moves.



Bob

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

"Mark" wrote in message
m.

The sidebands do look like FM. They also look like IM which I presume
you are calling AM.

Agreed

Note that both FM and AM produce symmetrical sidebands.

Agreed.

However when both AM and FM are present together, the
combination usually produces asymmetrical sidebands. This is because
the AM and FM sidebands have different phases above and below the
carrier. Since the sidebands in your experiment look pretty
symmetrical I would say that if AM and FM are present together, they
are not close to equal.

Agreed.

If they were close to equal, the sidebands would be very asymmetrical.

Agreed.

So how do we tell if the sidebands are FM or AM?

Suggestion. Send the signal through a 4 kHz BPF that is wide enough
to pass the sidebands but not wide enough to pass the 50 Hz or it's
harmonics.

That's an idea.

You should then be able to analyze this BP signal to see
if it is AM or FM. If it is AM, the envelope will vary at 50 Hz. If
it is FM, the envelope will be constant.

Its a mixture. Now the fun begins. There is an envelope, quite clearly at 50
Hz.

However, if we limit it heavily to forcably eliminate the envelope, there
are still 4 sidebands left.

Arny Krueger wrote:

"Bob Cain" wrote in message


Porky wrote:


True, but who's going to hear doppler shift at that level, even if
it does exist?:-)

To me it doesn't matter whether we can hear it or not. As
of now there is no predictive theory that yields
quantitative results we could test with experiment anyway.
I want to know whether or not it is a real phenomenon at all.


How are you doing with the 60KB or so of AES paper references that I posted
in RAP?

Not well without access to the papers. If you can point me
to at least one of them that solves the problem analytically
to yield a general mathematical description I'll purhase it.


Bob
--

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

A. Einstein

Arny Krueger wrote:

"Bob Cain" wrote in message


Bob Cain wrote:



Arny Krueger wrote:



Sorry Bob, but I'm not buying.


How about this, then:

1) It is the bulk velocity, the flow of air, at the rest position
that propagates out as the velocity wave.


Frankly, over my head.

That's hard to believe. What part of it evades you?



2) The bulk velocity at the rest position is the same as the surface
velocity of the piston.


Frankly, over my head.

Same.



And, finally:


3) In the frame of reference of the rest position of the
piston, no Doppler shift can be observed.


That seems wrong, because the following is right:

In the frame of reference of the piston, no Doppler shift can be observed.

If you are in the frame of reference of the piston, you're
going to get shanken _all_ to hell. :-)


Bob
--

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

A. Einstein

"Bob Cain" wrote in message

Arny Krueger wrote:

"Bob Cain" wrote in message


3) In the frame of reference of the rest position of the
piston, no Doppler shift can be observed.

That seems wrong, because the following is right:

In the frame of reference of the piston, no Doppler shift can be
observed.

If you are in the frame of reference of the piston, you're
going to get shanken _all_ to hell. :-)

Agreed.

Hey, you think getting zero Doppler is always painless? ;-)