VERIS 2 – Operation Manual - Page 24
Figure 8: Effect of Boundary Surfaces on Power Output
When choosing subwoofer location(s), be careful, however, not to sacrifice sonic quality for
sheer power. If the available wall or corner location results in the subwoofer being located
behind, or too close, to one or more open microphones, early feedback is likely to occur. If the
wall or corner location is too far away from the full-range loudspeaker(s), such a location may
result in the subwoofer being drastically out of time sync with one or more of the full-range
speakers.
Sometimes the sound quality of a wall or corner placement is not desirable, simply due to the
room’s acoustical properties. Keep in mind that when wall and corner locations
are
appropriate
for use, they’ll provide a tremendous increase in power output, but they may not always be
the best choice for sound
quality
.
(2)
Keeping the subwoofer(s) as close as possible to the mid and high loudspeaker(s) will
decrease phase irregularities and
time smear
. If subwoofer(s) are placed too far away
from the mid/high loudspeaker(s), the listener will experience a disjointed character to the
program material, causing the musicality of the system to suffer.
(3)
Although subwoofers are not particularly directional, still their acoustical output follows the
inverse square law. That is, every time the distance from the subwoofer to the listener is
doubled, the output level will decrease by 6dB. When covering a large space with multiple
subwoofers, it may be of benefit to space them some distance apart from one another to
even out the levels throughout the space. Typically, this would only be done if the
mid/high loudspeakers are also spaced apart from one another, such as in a distributed
system in a sports venue. Although this will help maintain an even level throughout the
listening space, there may be some areas that lie between two or more subwoofers that
experience a certain amount of power subtraction caused by
destructive interference
.
Destructive interference occurs when waveforms meet and are partially or wholly out of
phase with each other, due to unequal path lengths.
Conversely, if multiple subwoofers are located directly adjacent to one another, their power
output will add together almost seamlessly. This is known as
constructive acoustic addition
.
However, this may produce an undesirable hot-spot of low-frequency energy that might
possibly be too close to a seating area.
It’s always a good idea to experiment with trial locations before finalizing your installation
plan. Even a very experienced sound system designer cannot predict the precise effect that
one location may have over that of another, if he/she is not intimately familiar with the room
acoustics. When planning loudspeaker locations, it’s wise to discuss the matter with someone
who may have prior experience operating sound systems in that particular room, such as the
resident mixing engineer.
