Owner's Manual

V. ROOM ACOUSTICS, SUBWOOFER PLACEMENT, MULTIPLE
SUBWOOFERS & CONTROL SETTINGS
A. 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 our subwoofers.
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 reections. In larger spaces, sound has to travel to reach the reecting
surfaces and then to your ears, which means it has to be louder to begin with. With
traditional full-range speakers, that involves properly matching amplier power,
speaker sensitivity, impedance and power handling. Most of the power goes to
reproducing bass, so using powered subwoofers and separate midrange/treble
satellites allows for a conservative draw on power from your main amplier, while
ensuring a good match between the low-frequency amplier and the woofer.
After size, the most important aspect of a listening room is its shape. In any room,
sound reects off the walls, ceiling, and oor. 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 nd out what works best is by experimentation.
Speaker positioning may be fairly limited in your room to still get proper imaging, and
some of these positions may still result in standing waves. Use of a subwoofer or two
makes this more controllable. Positioning of the bass speakers has almost no impact
on imaging, so a subwoofer can be positioned with only standing waves in mind.
B. Subwoofer Placement
The loudest bass output from a subwoofer comes from corner placement. The
outward aring of walls from a corner focuses low frequencies, giving them no place
to go but toward the listener. In the case of subwooofers, there is no penalty in overall
balance for this maximal bass, since your main speakers can be located elsewhere.
In most cases, there should be plenty of bass from corner placement.
If you are seated in a null spot where sound from the subwoofer is cancelled or
diminished by out-of-phase reections, you will have to move either the subwoofer
or your listening position until you get the desired bass. 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
the opposite is happening, where direct and reected 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).
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