Room Acoustics
If you are critical about low-frequency response, there’s quite a bit of useful experimentation you can do, especially
in combination with the crossover, level, and phase controls of the BSW150.
Begin by considering the size of the listening room. The larger the volume of air a speaker must move, the more
acoustic output is required to achieve the sound levels you want. In smaller rooms, sound attenuation tends to be
offset by reinforcement from wall reflections. In larger spaces, sound has to travel to reach the reflecting surfaces
and then to your ears, which means it has to be louder to begin with.
After size, the most important aspect of a listening room is its shape. In any room, sound reflects off the walls,
ceiling, and floor. If the distance between two opposite parallel surfaces is a simple fraction of the wavelength of
a particular frequency, notes of that frequency will bounce back and forth in perfect phase—an effect called a
standing wave or room mode. At some point in the room, this note will be reinforced substantially; at others it will
cancel out almost entirely. If the prime listening seat is placed at either of these locations, the note will be a horrible
boom or virtually non-existent. Almost all rooms are susceptible to some standing waves at low frequencies, but
careful positioning of the speakers and the listening seat can minimize the effects. The only way to find out what
works best is by experimentation. Positioning of a bass speaker has almost no impact on imaging, so the BSW150
can be positioned almost anywhere.
Subwoofer Placement
The loudest bass output from a subwoofer comes from corner placement. The outward flaring of walls from a corner
focuses low frequencies, giving them no place to go but toward the listener.
If you are seated in a null spot where sound from the BSW150 is canceled or diminished by out-of-phase
reflections, you will have to move either the subwoofer or your listening position until you get the desired bass.
Adjusting the phase control 180 degrees may make a difference, especially if the null is a product of cancellations
caused by interaction with low frequencies from your main speaker(s). If the opposite is happening, where direct and
reflected bass waves converge in phase and produce too strong a peak at your listening position, you can change
position or change your sub’s level control (or possibly the crossover frequency chosen).
The best method for positioning the BSW150 is to put it in your listening chair, then play music with lots of bass
through the system (something with steady and obvious low frequencies). Move around the room and note where
the bass sounds best; if you place the BSW150 in that location, you should get the same bass performance. This
test only works if you have your ears at the same height as where the BSW150 will be, so you may have to get
down low. A recommended starting point for placement would be in either of the front corners of the room.
Multiple Subwoofers—Why Two Subs Are Better Than One
Sometimes the listening room is not conducive to achieving satisfying amounts or quality of bass. There are rooms
with troublesome dimensions, especially those that are more cubical. In such a case, two subwoofers placed
carefully to work with each other are recommended to handle acoustical anomalies. This can also be applied when
the problem is too much, or too uneven, bass. The overall system benefits from each subwoofer correcting the
acoustic problems caused by the other.
A very good starting point for positioning two subwoofers is to place one each on the centre of opposing walls.
Experimenting with positioning as previously described should be used for determining the location of the second
subwoofer, except in this instance one is listening for the minimum amount of bass output.
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