"Bob Cain" wrote in message

Arny Krueger wrote:


If you do the math, nonlinearities can't produce FM distoriton. You
need something that operates in the time domain, not the amplitude
domain.

If you do the math, FM distortion and linearity are mutually exclusive.

In many senses, I totally agree. However, Doppler distortion, while clearly
agreeing with the formal definition of nonlinear distortion, is not related
to any of the manifold other causes of nonlinear distortion in speakers.
Those other forms of nonlinear distoriton are due to changes of speaker
parameters, such as suspension compliance, as a function of the position of
the cone.

This is not debatable. Find a rigorous definition of linearity.

I think I just posted one.

I cheated, I picked it up from my www.pcavtech.com web site, I'm the author
of record. But, its pretty orthodox and I can find a dozen others online
that are about the same.

For example:

http://www.prosoundweb.com/install/s...rtion/dist.php

"I was mistaken this afternoon in defining distortion broadly instead of
nonlinear distortion. This latter gives rise to new frequencies not
originally present and which cannot be restored."

http://my.starstream.net/mk/Webpages...on_testing.htm

"Non-linear distortion refers to the generation of different frequencies
measured in a loudspeaker response that are not present in the original
stimulus."

http://www.daqarta.com/0diidist.htm

"This results when two or more different frequency components interact
within a nonlinear system. The output will then contain not only harmonics
of the original frequencies, but also components at sum and difference
frequencies that typically aren't harmonics of either input."


I've presented it but it doesn't
seem to have taken hold despite it being the bedrock of
linear systems theory.

There are in fact several different definitions of nonlinear distortion,
some that focus on the cause (transfer function curvature) and some that
focus on the effect (production of sounds not present in the input). In
general they are very closely related. Either is fine with me, even though
they don't mean identically the same.