Dear @dave_b This is a high-ligth of measured works made by Bruel&Kjeuer about sound/distortions. Unfortunatelly the ggraphics can't be seen here but the expert explanation speaks by it self:
"" Practical example s of Intermodulation Distortion (IMD) measurements
Intermodulation distortion can also be
used effectively to evaluate crossover
designs. If a transducer is excited with
a fixed low frequency test tone, for
example near resonance to cause large
diaphragm excursions, and another
test tone that sweeps up in frequency,
the resulting distortion will indicate
both amplitude modulation distortion
and Doppler frequency modulation distortion.
The Doppler phenomena in
loudspeakers occurs when a high frequency source is shifted by a low frequency.
Look at the IM distortion for the fullrange loudspeaker with its single driver
trying to reproduce the entire frequency Fig. 21a Harmonic Distortion components are attenuated by filter networks while 3rd
range (Fig. 22). There is a lot of 2nd
order difference frequency components remain the same level as the excitation frequencies,
order IM distortion. This is quite audi- fi andf2 (assuming 100% distortion)
12
ble in the midfrequency range. If a
chamber music duet with a cello and a
flute is played through a single driver,
the driver might cause the high frequencies of the flute signal to be modulated by the low frequencies of the cello
signal. ""
That CW woofer is just terrible even that you said " low distortions ".
R.