Bowers & Wilkins ASW825 - Manual (Page 7)

Positioning the subwoofer
Because the subwoofer produces only low-
frequency sounds, positioning is less critical
in some respects compared to full-range
speakers. Directional information is much
less precise and you have more choice
where to place the speakers to good effect.
This said, best results are obtained if the
subwoofer is placed between the satellite
speakers or in the vicinity of one of them. If
you use two subwoofers, it is best to put
one near each satellite speaker.
Placing the subwoofer behind the listeners,
even in surround sound installations,
generally gives inferior imaging, but may be
an acceptable compromise if domestic
considerations dictate.
As with all speakers, the proximity of room
boundaries affects the sound. Bass is
generally increased as more surfaces come
into close proximity with the speakers.
Unlike full-range speakers, however, you
can always restore the correct overall
system balance by adjusting the volume
level of the subwoofer. The more boost you
get from the room, the less hard the
speaker has to work; but there is a down
side. Corner positions often excite more
low-frequency room resonances, making
the bass more uneven with frequency.
There is no substitute for experiment as all
rooms behave differently, so try the
subwoofer in a variety of positions before
making a final decision. A piece of music
with a bass line ascending or descending
the musical scale is useful for assessing the
smoothness of the bass response. Listen
for exaggerated or quiet notes. Having a
separate subwoofer does enable you to
optimise for room resonances
independently from siting the satellite
speakers for best imaging.
If the subwoofer is to be used in a confined
space (eg in custom furniture), the space
must be ventilated to allow sufficient air to
circulate and cool the unit. Ask your dealer
for advice.
The subwoofer is supplied with four spike
feet. The spikes pierce through carpet pile,
giving a firm support directly to the floor
surface without crushing the pile.
If the unit is to be placed on a vulnerable
surface, such as a wooden floor, either
place a protective disc under each spike or
fit the four rubber feet in place of the
spikes.
When fitting either the rubber feet or the
spike feet, first screw the lock nuts fully
onto the thread and then screw the feet
fully onto the threaded inserts in the base
of the cabinet. If the unit rocks, loosen the
relevant two opposing feet until the support
is firm, then re-tighten the lock nuts to the
inserts.
Check that there are no cables under the
carpet that may be damaged by the spike
feet.
Do not walk the product on the spike feet
as this may cause them to become
detached from the cabinet and cause
damage.
Take care not to impale yourself with the
spike feet when moving the product.
Electrical connections
Disconnect all sound system equipment
from the power supply until the signal
connections have been made and checked.
This avoids the risk of damage whilst
connections are made or broken.
The function of the subwoofer is to receive
signals from the amplification chain and,
where necessary for 2-channel audio, split
the signal into low bass and higher
frequencies and feed the latter back out to
the satellite speakers. Left and right
channel inputs may be combined into a
single mono low bass feed to the
subwoofer drive unit if required.
The subwoofer will input and output line-
level signals via the RCA Phono sockets
located on the back panel.
Use the following table to select the correct
wiring method for your installation:
Application: Home Theatre
The subwoofer may be used with any
decoder that has a line-level subwoofer
output (normally from an RCA Phono
socket). Most decoders with integral power
amplifiers still output the subwoofer or
Low-Frequency Effects (LFE) signal at line
level.
• Decoder with one or more subwoofers
– fig. 3
Application: 2-channel audio
Separate pre- & power amplifiers:
a One or more subwoofers with output
combined into a single mono signal –
fig. 4
b Two subwoofers with separate left and
right signal – fig. 5
The subwoofer is not suitable for use with
2-channel integrated pre/power amplifiers.
Using more than one subwoofer
Using more than one unit in a single
installation can improve performance in the
following ways:
• Maintain stereo separation to the
lowest frequencies.
• Cope with larger listening rooms.
• Enable greater maximum sound output
– often useful for effectively
reproducing special effects in Home
Theatre applications.
• Smooth out the effects of low-
frequency room resonances.
If you are using two subwoofers for
2-channel audio, separation is improved if
each channel has its own subwoofer,
providing each one is placed close to the
relevant satellite speaker. Only use the
mono connection of figure 4 if you cannot
place each subwoofer close to its satellite
speaker.
Double-check the connections
Before auditioning the sound quality of your
new installation and fine-tuning it, double-
check the connections. All too often, users
complain that they cannot get a decent
sound however they set the controls, only
to discover something has been wrongly
connected. Make sure that:
• The phasing is correct – there should
be no positive to negative connections
to the satellite speakers. If something
is out of phase you may get a fuzzy
sound with an imprecise and floating
image, a lack of bass or a combination
of the two.
• There are no left to right mix-ups – this
can result, for example, in the
orchestra being the wrong way round
or, more disastrously, sounds on your
Home Theatre going in the opposite
direction to the action on the screen.
Switching on and off
We recommend that you switch the
subwoofer on before any power amplifiers
receiving signals from the subwoofer.
Similarly, when switching off, switch the
subwoofer off last.
The MODE standby/auto/on switch (4) does
not isolate the amplifier completely from the
power supply. It maintains a low-power
input to an auxiliary sensing circuit.
The switch (4) operates as follows:
On:
With the switch in this position, the
amplifier remains permanently on, and the
light (1) glows green.
Auto:
On first switching the subwoofer to Auto,
the amplifier becomes fully active and the
light (1) glows green. After a period of
about 5 minutes without an input signal,
the amplifier automatically reverts to
standby mode, and the light glows red.
When an input signal is detected, the
amplifier automatically becomes fully active
and the light glows green.
Standby:
In this position, the amplifier is in
permanent standby, and the light glows
red.
If the subwoofer is to be out of use for an
extended period of time, we recommend
you isolate it from the power supply, either
by using the POWER switch (11) or by
removing the plug from the power socket.
Setting the controls
There are 5 controls to consider:
• The VOLUME control (2)
• The LOW-PASS FREQUENCY
control (3)
• The PHASE switch (7)
• The LOW-PASS FILTER switch (6)
• The EQ (equalisation) switch (5)
The optimum settings depend on the other
equipment used with the subwoofer. If
using more than one subwoofer, ensure the
controls on each one are set the same.
Use with home theatre decoders
The B&W ASW Active Subwoofer is not a
THX® licensed component, but may be
used with a THX® controller if desired.
• Set the decoder VOLUME control to
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ASW 825-855 inside 8/6/05 4:35 pm Page 4