high frequency with a low frequency and applies that complex electrical
waveform to the speaker voice voil. The result is NOT a high frequency tone
riding on a low frequency tone, it's a single complex waveform containing
elements of both tones, and thus there is no Doppler distortion.

That doesn't make sense. To generate a frequency, the speaker has to
move back and forth at a certain rate. The higher the frequency, the
faster the rate at which it moves. Surely if we want to hear both
frequencies at once, the speaker has to vibrate at both speeds at once ?

If you look at a low frequency sine wave with an amplitude against time
graph, and SUM a much higher frequency much lower amplitude wave to it,
surely you'll see the original low frequency sine wave, but the line
itself instead of being a smooth sine wave, will be oscillating at the
high frequency.

This is what I imagine would happen anyway, I'm not near anything I can
test this with right now. Just looking at what the line is doing will
then surely tell you what the speaker is doing ? Surely it'll be
following the wave ?

So, the speaker would be slowly moving back and forth, following the
amplitude of the low frequency signal, but as it moves back a forth,
it'll be oscillating a small amount back and forth at its current
position in the low frequency wave because that is what the input signal
is doing.

IMHO at least ....

Here is an example;

Our keyboard player once made his keyboard output such a low frequency
signal, that you could watch the speaker slowly move back a forth quiet
far, perhaps once every second. Are you telling me that, if I "mixed" a
high frequency with that signal, the speaker would be no longer moving
back and forth slowly about once per second ?

--
Mark Simonetti.
Freelance Software Engineer.

"Mark Simonetti" wrote in message

high frequency with a low frequency and applies that complex
electrical waveform to the speaker voice voil. The result is NOT a
high frequency tone riding on a low frequency tone, it's a single
complex waveform containing elements of both tones, and thus there
is no Doppler distortion.

That doesn't make sense. To generate a frequency, the speaker has to
move back and forth at a certain rate. The higher the frequency, the
faster the rate at which it moves. Surely if we want to hear both
frequencies at once, the speaker has to vibrate at both speeds at
once ?

The speaker is one entity, so it has only one speed at a time. In your case
the speaker's speed is the sum of the two speeds. You later talk like you
believe this. So why not say it up front?

If you look at a low frequency sine wave with an amplitude against
time graph, and SUM a much higher frequency much lower amplitude wave
to it, surely you'll see the original low frequency sine wave, but
the line itself instead of being a smooth sine wave, will be
oscillating at the high frequency.

Agreed

This is what I imagine would happen anyway, I'm not near anything I
can test this with right now. Just looking at what the line is doing
will then surely tell you what the speaker is doing ? Surely it'll be
following the wave ?

Pretty much.

So, the speaker would be slowly moving back and forth, following the
amplitude of the low frequency signal, but as it moves back a forth,
it'll be oscillating a small amount back and forth at its current
position in the low frequency wave because that is what the input
signal is doing.

Ironcially, the velocity due to the lower frequency may be the greater of
the two velocities that are summed together.

IMHO at least ....

Here is an example;

Our keyboard player once made his keyboard output such a low frequency
signal, that you could watch the speaker slowly move back a forth
quiet far, perhaps once every second. Are you telling me that, if I
"mixed" a high frequency with that signal, the speaker would be no
longer moving back and forth slowly about once per second ?

Of course it will. And its instanteious velocity is added to the
instantaneous velocity due to the upper note.

Of course it will. And its instanteious velocity is added to the
instantaneous velocity due to the upper note.

Okay, but it seems like people are saying that this isn't the case, and
is the reason doppler distortion would NOT occur, which seems plain
bizzare, IMHO. Surely, as the lower frequency moves the cone back and
forth, which at the same time is vibrating to create the higher
frequency, that is IDENTICAL to moving a single vibrating source back
and forth, like the train analogy (except the train doesn't move back
and forth unless the driver is very confused). Therefore, the doppler
effect surely DOES occur.

It just seems really obvious, so I must be missing the whole point of
this, I'm no physics scientist !

--
Mark Simonetti.
Freelance Software Engineer.

"Mark Simonetti"

Surely, as the lower frequency moves the cone back and
forth, which at the same time is vibrating to create the higher
frequency, that is IDENTICAL to moving a single vibrating source back
and forth, like the train analogy (except the train doesn't move back
and forth unless the driver is very confused). Therefore, the doppler
effect surely DOES occur.

It just seems really obvious, so I must be missing the whole point of
this, I'm no physics scientist !



** The matter is intuitive to many - but forever obscure to those with
no mental capacity to imagine the situation in their heads. It pretty much
divides up between the science types ( using mental, physical models ) and
the arts subject types ( using only grammar and phrase matching).

The fact that cones have **vastly greater** excursions at low frequencies
than at high ones - even for the same SPL - is at the heart of the matter
and clearly bamboozles as well.

The fact that those large low frequency excursions have the greatest
velocity also confounds the easily confoundable.





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

Phil Allison wrote:
no mental capacity to imagine the situation in their heads. It pretty much
divides up between the science types ( using mental, physical models ) and
the arts subject types ( using only grammar and phrase matching).

I often find this. When designing and writing software for instance at
work, I can see it all in my head, the mechanisms, how things interact
and such like. As soon as I try and explain it verbally to someone, I
find it difficult to transfer to language. I'm okay if I have time to
produce a document though, because then I have time to translate the
visualisation into words, and I can use diagrams.

In my original post about this, I had the same problem, I wanted to draw
diagrams showing the waves being summed, and the speaker in its
different position, etc.

--
Mark Simonetti.
Freelance Software Engineer.

"Mark Simonetti"

no mental capacity to imagine the situation in their heads. It pretty
much
divides up between the science types ( using mental, physical models )
and
the arts subject types ( using only grammar and phrase matching).

I often find this. When designing and writing software for instance at
work, I can see it all in my head, the mechanisms, how things interact
and such like. As soon as I try and explain it verbally to someone, I
find it difficult to transfer to language. I'm okay if I have time to
produce a document though, because then I have time to translate the
visualisation into words, and I can use diagrams.

In my original post about this, I had the same problem, I wanted to draw
diagrams showing the waves being summed, and the speaker in its
different position, etc.



** The lack of the facility to post sketches and diagrams on usenet is a
*real* drawback. When I need to explain stuff to non-technical folk ( and
some technical ones too) I often reach for my pen and paper !!!!

Then, on second thoughts, the sketches that might appear most often could
be kinda pornographic in nature ;-)



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

Phil Allison wrote:
Then, on second thoughts, the sketches that might appear most often could
be kinda pornographic in nature ;-)

That might not be a bad thing, I mean if it helps get the point across,
right? All in the aid of science and all that ;-)

--
Mark Simonetti.
Freelance Software Engineer.

In alt.music.home-studio,rec.audio.tech,rec.audio.pro, "Phil Allison"
wrote:

** The lack of the facility to post sketches and diagrams on usenet is a
*real* drawback. When I need to explain stuff to non-technical folk ( and
some technical ones too) I often reach for my pen and paper !!!!

Draw the pics on paper, scan them in, put the files (reasonably
compressed .jpg, please) on a website, and post the URL's in your
message.

Then, on second thoughts, the sketches that might appear most often could
be kinda pornographic in nature ;-)

Use Geocities, they're slow to clean up smut on their server.




.......... Phil




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

"Mark Simonetti" wrote in message

Of course it will. And its instanteious velocity is added to the
instantaneous velocity due to the upper note.

Okay, but it seems like people are saying that this isn't the case,
and is the reason doppler distortion would NOT occur, which seems
plain bizzare, IMHO.

So bizarre, that it is in fact fallacious.

Surely, as the lower frequency moves the cone
back and forth, which at the same time is vibrating to create the
higher frequency, that is IDENTICAL to moving a single vibrating
source back and forth, like the train analogy (except the train
doesn't move back and forth unless the driver is very confused).

Agreed.

Therefore, the doppler effect surely DOES occur.

Agreed.

It just seems really obvious, so I must be missing the whole point of
this, I'm no physics scientist !

I've got two years of physics, an undergraduate degree in engineering and
completed most of my MSE except for my thesis project (wife's pregnancy
ended that). I've also measured it quite conclusively in the lab. I've been
reading papers about it for like 30 years in the JAES and JASA. Yes, I think
that Doppler distortion exist in speakers, but no I don't think it is a
serious issue. In contrast the AM distortion in speakers is a very serious,
audible issue.

Arny Krueger wrote:

I've got two years of physics, an undergraduate degree in engineering and
completed most of my MSE except for my thesis project (wife's pregnancy
ended that). I've also measured it quite conclusively in the lab. I've been
reading papers about it for like 30 years in the JAES and JASA. Yes, I think
that Doppler distortion exist in speakers, but no I don't think it is a
serious issue. In contrast the AM distortion in speakers is a very serious,
audible issue.

This is a reasonable assessment of the situation. The thing about doppler
modulation, though, is that it's really interesting and the math is a lot
of fun. Not like typical AM distortion from amplitude nonlinearities, which
is dull, even if it's a more significant problem. So I think folks should
continue investigating doppler distortion because it's an interesting problem
even if not a terribly important one.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message

Arny Krueger wrote:

I've got two years of physics, an undergraduate degree in
engineering and completed most of my MSE except for my thesis
project (wife's pregnancy ended that). I've also measured it quite
conclusively in the lab. I've been reading papers about it for like
30 years in the JAES and JASA. Yes, I think that Doppler distortion
exist in speakers, but no I don't think it is a serious issue. In
contrast the AM distortion in speakers is a very serious, audible
issue.

This is a reasonable assessment of the situation. The thing about
doppler modulation, though, is that it's really interesting and the
math is a lot of fun. Not like typical AM distortion from amplitude
nonlinearities, which is dull, even if it's a more significant
problem. So I think folks should continue investigating doppler
distortion because it's an interesting problem even if not a terribly
important one.

Thanks, Scott. The other thing about Doppler is that it is in some sense
irreducable, and even something that modern speaker development trends seem
to want to increase.

Some of my informants argue that in fact speakers are about as linear as
they ever will be, and that the only remaining approach is to make them
cheaper, smaller, and put their nonlinearities where they won't sound so
objectionable.

This whole discussion traces back to another discussion on another audio
groups about a month ago. My opponent in that discussion seems to have
considerably changed his position in the past month in a good way, but he
still abuses my name. So goes life!

Arny Krueger wrote:

Some of my informants argue that in fact speakers are about as linear as
they ever will be, and that the only remaining approach is to make them
cheaper, smaller, and put their nonlinearities where they won't sound so
objectionable.

If speakers are as linear as they ever will be, I'm giving up this whole
industry and going out to listen only to live music. If this is as good
as it gets, it's a total waste.
--scott


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

Scott Dorsey wrote:

So I think folks should
continue investigating doppler distortion because it's an interesting problem
even if not a terribly important one.

Mostly agreed. The extent to which unbelievably small
effects are claimed to be audible on the ProAudio mailing
list, if they are other than imagination, does push any such
effects like we are talking about into an arena at least
worth discussing, if not important. It wouldn't take much
_at all_ to swamp the things they consider very important.


Bob
--

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

A. Einstein

"Bob Cain" wrote in message

Scott Dorsey wrote:

So I think folks should
continue investigating doppler distortion because it's an
interesting problem even if not a terribly important one.

Mostly agreed. The extent to which unbelievably small
effects are claimed to be audible on the ProAudio mailing
list, if they are other than imagination, does push any such
effects like we are talking about into an arena at least
worth discussing, if not important.

The point is well taken. Gosh, I even brought it up about a week ago and our
resident opamp wine tasters completely missed it.

Go figure!

It wouldn't take much
_at all_ to swamp the things they consider very important.

Speaker Doppler as insignificant as it is, is positively huge compared to
the errors that a common nasty old 5532 or TL072 makes in most audio
circuits.

Mark Simonetti wrote:

Of course it will. And its instanteious velocity is added to the
instantaneous velocity due to the upper note.


Okay, but it seems like people are saying that this isn't the case, and
is the reason doppler distortion would NOT occur, which seems plain
bizzare, IMHO.

In some circumstances it does and in others it doesn't but
that isn't the reason, at any rate, for either result.


Bob
--

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

A. Einstein

"Bob Cain" wrote in message
...


Mark Simonetti wrote:

Of course it will. And its instanteious velocity is added to the
instantaneous velocity due to the upper note.


Okay, but it seems like people are saying that this isn't the case, and
is the reason doppler distortion would NOT occur, which seems plain
bizzare, IMHO.

In some circumstances it does and in others it doesn't but
that isn't the reason, at any rate, for either result.


My position is that the speaker's motion does NOT directly produce the
sound, so there is no tone riding on any other tone coming from the speaker.
The complex motion of the speaker cone corresponds exactly with the
compression and rarefaction of the air in front of it, and any instantaneous
position of the cone is directly related to the corresponding level of
compression or rarefaction of the complex acoustic wave. Adding a DC
component doesn't matter, because the excursion levels will still be exactly
the same as long as the linear excursion factor of the speaker is not
exceeded, the center position will just be moved a bit. Slowly varying DC
doesn't affect it either, since the variation becomes part of the acoustic
wave being produced, whether we hear it or not. The flaw there was assuming
that because we couldn't hear it, wasn't a sound wave. The only thing that
can cause Doppler shift in a speaker is physically moving the speaker
relative to the listener with some force other than that producing the
complex wave driving the speaker motor.
Here's another way of looking at it, putting a sound wave through a hole
in the wall can't produce Doppler shift, no matter how many tones are in the
waveform, and a speaker is effectively an artificial hole in the wall, in
that the effective sound source isn't the speaker any more than it is the
hole in the wall. Does anyone here think that if you stretched a thin
diaphragm over a hole in a soundproof wall and had a band playing behind it,
the diaphragm would cause Doppler Distortion? The speaker, provided it isn't
exceeding its linear limits, is effectively exactly the same thing for all
practical purposes. Instead of being driven by the sound source in the other
room, it's driven by the electrical equivalent of the sound source in the
other room. Can any of you provide an explanation of how an acoustic wave
driving a diaphragm and passing the soundwave
through it is in any way different than the diaphragm being driven by a
motor being supplied with the exact electrical analog of that acoustic wave?
And by that I mean that the difference will be such that the electrically
driven one will produce Doppler distortion while the acoustically driven one
doesn't.