Specifications

M&K Sales Training Outline
page 8
May 98
http://www.mksound.com
36 dB/octave Low-Pass
filters make M&K
Powered Subwoofers
truly non-directional
Powered Deep Bass Subwoofer Amplifiers
"Q" is a measure of quality that involves the speaker's transient per-
formance, with a low "Q" being better. Subwoofers with passive ra-
diators, vented boxes (bass reflex) or bandpass designs use air in a
chamber or port as a high Q resonator, much as a bottle filled with
water whistles at one frequency when you blow across its opening.
The vent "tunes" the speaker to a given frequency, which then be-
comes essentially its low frequency limit.
The purpose of these ports or passive radiators is to resonate the
cabinet at some frequency, which, if done properly, can increase the
speaker's output by 3 to 6 dB at that frequency.
But these high Q systems have an unavoidable tendency to reso-
nate (or "ring"), much as a tuning fork continues to sound long after it
is struck. M&K's sealed-box low Q sealed box designs, tightly stuffed
with special sound-absorbing material (which cannot be used with a
vented speaker), produce a solid output without ringing, down to fre-
quencies below 20 Hz.
Every element of an M&K subwoofer, from the driver to the enclo-
sure and the amplifier is very tightly damped (low Q), so the combina-
tion achieves extremely tight and articulate musical bass.
The M&K low-pass filter is an important element in the sound qual-
ity of M&K Subwoofers. Our 36 dB/octave filters have a sufficiently
sharp rolloff to truly eliminate the reproduction of frequencies above
125 Hz, where subwoofer output is unwanted.
Virtually all competitive subwoofers have a shallower filter slope,
meaning they reproduce audible information such as voices at 200
Hz and above. This degrades the system’s overall sound quality and
means that listeners may be able to identify the location of the sub-
woofer.
When customers say they can locate a subwoofer in a room, it is
because of this higher frequency reproduction. You can tell these cus-
tomers that M&K subwoofers are
truly non-directional.
There are actually two filters in the circuit. The first is user-adjust-
able through the FILTER knob on the amplifier back panel. This lets
the user set the “knee” of the rolloff curve (3 dB down point) anywhere
between 50 and 125 Hz. This first filter rolls off the woofer at a rate of
12 dB/octave. The second filter comes into play at 125 Hz, and adds
a second filter to produce a total rolloff of 36 dB/octave.
Control of system "Q" to
deliver tight, musical bass