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
Subwoofer Placement
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. It still may be too much bass for your room or (more particularly)
your favorite listening spot in the room, but 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 rotating the variable 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 can—if
you like—deal with that both with changes in placement or in the position of your
sub's level control (or, less likely but possible, the crossover frequency chosen). We
say “if you like” because there is no such thing as too much bass for some listeners,
and we don't want to be dogmatic. You are definitely the one who has to be pleased,
unless your Significant Other chimes in to the contrary.
As you go outward from the corner along one wall or another, the general consensus
(with which we tend to agree) is that while bass output diminishes somewhat, it also
becomes more uniform throughout the room, with fewer of the “standing waves” that
produce peaks and nulls at various points.
Chances are things won't be so simple, so the best method for positioning a
subwoofer, although a rather undignified-looking one, is to put the subwoofer in your
listening chair, then play music with lots of bass through the system something with
steady low frequencies (such as organ music) or continuous test tones, not movie
material. Move around the room and note where the bass sounds best; if you place
the subwoofer there and yourself in your chair, you should get the same bass
performance. Bear in mind that the test only works if you have your ears as high off
the floor as the subwoofer will be, so don't be afraid to crawl around. A recommended
starting point for the placement of this subwoofer would be in either of the front
corners of the room (on either side of the main speakers).
Rather than mounting your HD Sub in the open you might choose to mount it within a
cabinet or “wall unit” intended for hiding away the components of your home theater.
When cabinet mounted a few extra details must be attended too. The woofers on the
HD Subs are placed on the front face and the passive radiators on the sides where
they can all be placed reasonably close to a “sonic exit” of the cabinet. The cabinet
may have a front door with a grille (cloth or latticework). It may also have a solid front
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