How Many Subwoofers - Niles PSW8 Installation And Operation Manual

How Many Subwoofers?

For most applications a single PSW8's is
appropriate. However, in large rooms, high
performance listening rooms or in home
theaters, an array of two or more PSW8s
will deliver astounding results. Unlike
other subwoofer systems, a Niles
Subwoofer Array is concealed. Consider
the distance between the subwoofer(s) and
the listener, the size of the amplifier, and
the desired quality and volume of sound
when deciding how many PSW8s to install
in your home.
Decibels and Power
65dB Conversation at three feet.
75dB Sewing Machine at three feet.
85dB Vacuum Cleaner at 10 feet.
95dB Subway Train entering a station
at 20 feet.
3dB The smallest difference in volume
the human ear can easily detect.
10dB Perceived as twice as much loud-
ness if it is an increase (half as
much if it is a decrease).
Any speaker requires twice as much
amplifier power to increase 3dB and ten
times as much power to increase 10dB.
Comparison of 1, 2 or 4 Subwoofers
16' x 18' x 8' Room @ 12'
25 Watts
1 Sub 95dB
2 Subs 100dB
VLSA of 4 Subs 103dB
2 x Watts = 3dB Increase in Volume.
2 x Subs = 3dB Increase in Volume.
2 x Subs = 1/2 the subwoofer excursion for
the same volume.
If you double the distance from the sub-
woofer to the primary listening position
you decrease the volume by 4 to 6dB.
Single Stereo Subwoofer
One PSW8 can produce the bass sound
from both the left and the right channels
because of its unique dual voice coil
design. One voice coil powers the left chan-
nel and the other powers the right channel.
A stereo crossover divides the signal and fil-
ters it according to the settings of the switch-
es on the front panel. A single stereo sub-
woofer is compatible with any 4 ohm stable
amplifier. Eight ohm stable amplifiers may
be used with a Niles IM volume control (see
Impedance section on Page 7)
Dual Subwoofer Systems
Using two PSW8 subwoofers in a system
raises the maximum attainable volume of
the system by 3dB. Additionally, at lower
volumes, excursion — and therefore distor-
tion levels — are reduced. In a large room,
or a home theater system, the effect on
bass quality is extremely desirable.
Another 2dB increase is possible if the
voice coils of each are PSW8 paralleled.
This requires a multi-channel amplifier or
an amplifier capable of driving the 2 to 2.6
ohm load of the overall system.
VLSA Installations
A Very Large Subwoofer Array (VLSA)
installation lowers the amount of excur-
sion required to achieve a high sound
pressure level. Lowering excursion dra-
100
Watts
matically improves the quality of the
101dB
sound. VLSA installations are most appro-
106dB
priate when the listener appreciates detail
109dB
and bass extension, but must have a con-
cealed installation. A VLSA of four sub-
woofers must have a multi-channel ampli-
fier with one channel assigned to each
subwoofer. (See Figure 7).
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