unless any of these dimensions are the same. An ideal listening room would
have no parallel surfaces—an unusual situation, to say the least—so that such
waves would not establish themselves. The worst kind of room is a perfect cube.
Almost all rooms are susceptible to some standing waves at low frequencies, but
their effects can be minimized by careful positioning of both the speakers and the
listening seat. Moving either of these even a few inches is sometimes enough to
cure—or create—an intolerable sound. The only way to find out what works best
is by experimentation.
With full-range speakers, the range of places you can put the speakers and still
get proper imaging may be fairly limited, and some of these positions may result
in standing waves that can't be tamed. Things are more controllable through the
use of a subwoofer or two. Positioning of the bass speakers has almost no
impact on imaging, so a subwoofer can be located with only standing waves in
mind.
In-Wall Subwoofer Placement
The CWA-1 can be used with nearly any passive subwoofer. This includes the
PSB CWS8 in-wall subwoofer as well as future models, both in-wall and
enclosed. Obviously an in-wall subwoofer must be located on the wall surface
while a conventional subwoofer allows more freedom of location. There is no
argument among audiophiles that the loudest bass output from a subwoofer
comes from corner placement. The natural megaphone-like flaring outward of
walls from a room corner focuses low frequencies—giving them no place to go
but toward you. In the case of subwoofers, there is no automatic penalty in giving
overall balance for this maximal bass, since your main speakers can be located
elsewhere. Unless you are seated in a “null” spot, where sound from the sub is
cancelled or diminished by out-of-phase reflections from elsewhere, there should
be plenty of bass from corner placement.
If you are seated in such a null spot, your only real choices are generally to move
either the subwoofer or your listening position until bass returns to the point that
satisfies. Cranking up the level control or changing the crossover point almost
certainly won't help much. But flipping the phase control 180 degrees sometimes
may make a difference, especially if the null is a product of cancellations caused
by interaction with low frequencies from your main speakers
If you are in the opposite sort of situation, where direct and reflected bass waves
converge in phase and produce a strong peak at your listening location, you
Most bass output,
even bass response
Moderate bass output
,
more even bass response
6
