PSB Speakers PSB SubSeries 500 Guide D'utilisation page 7

V. Room Acoustics, Speaker Placement, Multiple
Subwoofers and Setting Controls
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.
Since the earliest days of high fidelity, one of the main challenges for the
designers of speakers, and of their users, has been management of the
lowest frequencies—the deep bass. Many of the most notable
developments in speaker design have been made with a view to getting
more bass output from smaller boxes.
One consideration is the size of the listening room. The larger the
volume of air a speaker must excite, the more acoustic output you will
require from it to achieve the sound levels you want. In any environment,
sounds attenuate as you move farther away from their source, but in
smaller rooms that tends to be offset by reinforcement from wall
reflections. The larger the space is, the farther the sound has to travel
both to reach the reflecting surfaces and then to get to your ears, which
means it has to be louder to begin with.
With traditional full-range speakers, that involves an intricate matching
act between amplifier power, speaker sensitivity, impedance and power
handling. But the bulk of the power goes to reproducing bass, so the use
of powered subwoofers and separate midrange/treble satellites both
allows you to be conservative in the amount of
produces, and ensures a good match between the low-frequency
amplifier and the woofer it is paired 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. The standing waves are different between floor
and ceiling, side walls, and end walls, 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
power your main amplifier
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