@dave_b : "
I knew that! ". So you are wrong exactly as him because the CW woofer handled frequency from around 35hz to 800hz frequenciesand develops high IMD no matters what that can be fixed using a subwoofers where both CW and subs crossover 80-100hz. You already know the instruments including human voice that are inside that frequency range and its reponse are modulated but the woofer low frequency.
These comes from Vandersteen:
"""
Given these stipulations, a pair of powered
subwoofers can provide the following benefits:
Page 14 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
1. Better performance from your speakers.
Full range loudspeakers utilize the same
driver to reproduce both the bass range of frequencies
and at least part of the midrange. For
optimum reproduction of midrange frequencies
little cone movement is required, and a relatively
small driver is necessary to provide quick
response and good dispersion.
Low frequencies require lots of air movement,
demanding greater cone area and more cone
movement. In engineering terms, the back-andforth
movement of the cone is called excursion.
Cone excursion quadruples with each halving of
frequency.
Good midrange reproduction requires the
use of moderately-sized drivers and good bass
reproduction requires lots of cone area, so most
full range speakers compromise the quality of
both bass and midrange by utilizing woofers that
are too small to provide good bass yet too large to
deliver the best midrange quality.
The cone of the 8-inch or 10-inch woofer
typically found in a full range loudspeaker will be
required to make peak-to-peak excursions of perhaps
an inch to deliver audible levels of output at
40Hz and it will have to do this while producing
300Hz (or higher) midrange signals at the same
time. A 6.5-inch woofer will make a better
midrange driver but it will have to work even
harder to deliver low frequencies and IM distortion
in the midrange will rise.
Intermodulation distortion occurs when
one frequency modulates (alters by its frequency)
another. Peak-to-peak cone excursions of an inch
or more, which may be required to reproduce a
40Hz signal, will have a substantial effect on a
signal at 300Hz. The 300Hz signal will increase
slightly in frequency when the cone is moving
towards the listener to reproduce the 40Hz portion
of the signal, and decrease in frequency when the
cone is moving away from the listener. This is
only one mechanism of IM distortion, which is
sometimes called Doppler distortion. There are
other forms of IM distortion.
All dynamic drivers exhibit some nonlinearity
in outward versus inward cone movement.
High cone excursion exacerbates nonlinear driver
response and causes harmonic distortion.
Harmonic distortion occurs when a harmonic
(multiple) or side-band of the desired signal is
produced due to nonlinear behavior of the electrical,
magnetic or mechanical mechanism of the
driver. If you want to reproduce 40Hz and you get
some output at 160Hz as well, that�s harmonic
distortion.
The results of high excursion of the
woofer cone are intermodulation distortion of the
midrange signal and increased harmonic distortion
of the bass signal. And there�s more.
The small woofers required to maintain
reasonable midrange performance in a full range
speaker don�t do a very good job of reproducing
the lowest bass frequencies but they do put a lot
of energy into the speaker cabinet structure and
this is very detrimental to sound quality.
As the woofer cone makes these large
mechanical movements to pressurize and rarefy
air, an equal and opposite force is applied to the
woofer basket, or frame, which is attached to the
speaker structure. This force excites resonances in
the cabinet structure and tries to move the whole
speaker back and forth. Cabinet resonances color
the sound in the midrange. Cabinet movement
distorts high frequencies.
A backward and forward motion of just a
few thousandths of an inch may represent a major
percentage of the total excursion of the tweeter
diaphragm as it attempts to reproduce subtle high
frequency details. The result of structural movement
is IM distortion of the midrange and high
frequencies.
If you are skeptical about the sonic consequences
of woofer energy moving the speaker
cabinet, think about speaker spikes. A reduction in
cabinet motion is the main reason that spikes
beneath the speaker improve sound. Remove the
spikes and see (no, hear) what happens.
As you can see, a full range loudspeaker is
a bundle of compromise. It is asked to perform
many conflicting tasks. .............."""
Why insist that the CW has not a IMD problem?, well is up to you.
R.
