Bob Cain wrote in message ...
Bob Cain wrote:


snip.....snip

The answer turns out to be simple. If the velocity and
position of the particles moving about their rest position
at the origin are
Vp(t) = Sp'(t)

snip......snip

The Doppler distortion in a plane wave is a consequence of
the non-linear relationship between the signal motion
imparted to the air by the driver and the flow velocity
(pressure) at a point about which that motion is manifest
and measured.

For a two tone Vd(t), one at 40 Hz and another at 2 kHz and
allowing a motion of 2 cm (a reasonable Xmax for a two way
system) the RMS IM distortion sidebands about the 2 kHz
fundamental near the speaker face are on the order of .2% of
that fundamental. While of some signifigance compared to
other portions of an audio chain, it probably isn't for a
loudspeaker given its other distortion mechanisms.
Bob

Does your prediction of 0.2% distortion apply to the situation of a
piston in a tube or a piston in an infinite baffle, or doesn't it
matter?