Randy Yates wrote:
ruffrecords writes:


PenguiN wrote:

The sound produced by the speaker happens because the speaker is driven
None of those approximates in any way, or
is a valid anology for a loudspeaker producing a complex waveform that comes

from only one source, the complex electrical waveform driving the speaker

motor. All the other anologies have two sources, one for the low frequency
motion and one for the high frequency sound, NOT a valid anology for what
happens when a speaker reproduced a complex waveform.

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

Picture the largest loudspeaker in the universe sitting outside

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

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


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


Consider this gedanken: Place a 4-inch speaker on the cone of a 14-foot
speaker. Now, the two speakers are fed different signals.

Consider this. place a 14ft speaker next to a 4inch speaker and feed
them different signals. Is there Doppler? No


The difference between receiving two such summed signals electrically
versus acoustically is that one has the physical phenomenom of the
propagation of sound through the air in one case and not in the other.

I did not mention electrical adding of the signals.



Get out a physics book and read about Doppler. The explanation of
how the observed wavelength changes when there is a relative velocity
between the source and observer should make you a believer that this
is precisely the scene in a speaker reproducing two frequencies.

get an electrical test book and read about linear superpostion.

Ian