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A s everyone—at least, every-
one who reads this magazine—knows, the
sound of a subwoofer in a room depends
not only on the subwoofer itself, but also on
the room and the placement of the sub-
woofer in the room. You can have a sub-
woofer that’s a sterling performer when
measured anechoically, but that perfor-
mance may not be realized in a given home-
theater setting. While some of us are in the
fortunate position of being able to build a
dedicated home-theater room of ideal pro-
portions, most of us are stuck with the
rooms we’ve got, which leaves subwoofer
position as a variable to be optimized.
There are formulas and computer pro-
grams that will suggest subwoofer position-
ing, but, in my opinion, these are not as use-
ful as they seem. The ones I’m familiar with
all use a mathematical model that assumes
a shoebox-shaped room with no openings
in the walls, and walls of infinite rigidity.
Real rooms may be L-shaped and have
doors, archways, closets, skylights, and
cathedral ceilings—variables that can’t be
plugged into the formulas. Real walls typi-
cally have rigidity that is considerably less
than infinite, which can affect the useful-
ness of the result in ways that are often
unpredictable.
One bit of advice that’s hard to argue with
is that the subwoofer should be moved
around until you find the position that pro-
duces the best bass—i.e., the greatest exten-
sion, the most output, the flattest frequency
response, and the smoothest integration
with the main speakers. Fair enough, but
even if you ignore the possibility that you’ll
have to make tradeoffs among the different
criteria of subwoofer performance (for
instance, the position that gives you the high-
est output might not produce the smoothest
integration), this approach assumes that you
have considerable flexibility in subwoofer
positioning. Again, the reality may be quite
different. The position that’s ideal for the sub-
woofer may be exactly where you have the
equipment rack, with no other convenient
place in the room to put the equipment. Or
the subwoofer might sound best when
placed in a position that will almost guaran-
tee that people will trip over it or its cables.
Equalization
One approach to improving in-room sub-
woofer performance is equalization: atten-
uating the peaks and boosting the valleys, a
process intended to produce an overall
more linear frequency response. Unfortu-
nately, there are several pitfalls to using
conventional equalization in this fashion.
First, boosting a frequency that corre-
sponds to a dip in the frequency response is
not advisable. A dip usually indicates
acoustic cancellation, and boosting the
level at this frequency is like feeding power
into an acoustic black hole. You’ll end up
pushing the subwoofer to high output lev-
els, with little to show for it, except possibly
driving the woofer into audible distortion.
Attenuating a peak might be effective,
Interlude IL120s ported active subwoofer
Driver: one 12" C.M.M.D. cone
Frequency response: 28–150Hz, ±3dB
Amplifier output: 500W (20–150Hz,
<0.1% THD)
Crossover frequencies: 50–150Hz,
24dB/octave, continuously variable
Controls: subwoofer level, phase (0°/180°),
crossover frequency, R.A.B.O.S. (see text)
Finishes: cherry, natural maple, onyx-onigre
Dimensions: 17
1
⁄2" × 17
1
⁄4" × 19
3
⁄4"
(H×W×D)
Weight: 45 lbs.
Price: $899; Bass Optimization Test &
Measurement Kit, $59.95
Manufacturer
Infinity Systems
250 Crossways Park Drive
Woodbury, NY 11797
tel. (800) 553-3332
fax (516) 682-3524
www.infinitysystems.com
SPECIFICATIONS
EQUIPMENT REPORT
Infinity Systems
Interlude IL120s
Robert Deutsch
SUBWOOFER
74 Stereophile Guide to Home Theater • November 2001
108-0111-Infin-p074-76,78x 1/24/02 1:32 PM Page 74