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

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

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

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

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

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

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 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

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 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

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 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:

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:

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 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

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

"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.

"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.

"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

"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

"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.

"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.

"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! ;-)

"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! ;-)

"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.

"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.

"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.

"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.

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.

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 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 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.

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.

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.


** 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

"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

(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.

(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.

"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

"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

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."

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."