Bowers & Wilkins AS2 User Manual

Page 7

them. If you use two subwoofers, it is best
to put one near the left and one near the
right 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.

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 subwoofer will input both line-level
signals via the RCA Phono sockets and
speaker level signals via the binding posts
located on the back panel.

Use the following guide to select the
correct wiring method for your installation:

Application: Home Theatre (figure 4)

Connect the subwoofer LINE IN socket (2)
to the line-level output of the processor
marked LFE or SUBWOOFER, using a
suitable coaxial interconnect cable. If using
more than one subwoofer, daisy chain them

together by connecting the LINK OUT
socket (3) of the first to the LINE IN socket
(2) of the next.

Application: 2-channel audio

For 2-channel operation, use speaker level
rather than line level connections. The
subwoofer presents a high impedance load
to the stereo power amplifier and takes
very little current, so may be connected in
parallel with the main speakers with no
adverse effects.

Using one subwoofer (figure 5)

The left and right channels are both
connected and summed in the subwoofer
amplifier.

Using two subwoofers (figure 6)

If one subwoofer can be placed close to the
left speaker and the other close to the right
speaker, stereo separation is best
maintained by connecting each subwoofer
to a separate output channel of the amplifier.

If the subwoofers cannot be placed close
to the main speakers, better results may be
obtained by feeding the left and right
channels to both subwoofers, connecting
both subwoofers as shown in figure 5 and
described above in the section “Using one
subwoofer”.

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.

Double-check the connections

ENSURE THAT THE VOLTAGE INDICATED
ON THE AMPLIFIER PANEL MATCHES
THAT OF THE POWER SUPPLY.

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 after any equipment feeding
signals to it. Similarly, when switching off,
switch the subwoofer off first.

The MODE standby/auto/on switch (7) does
not isolate the amplifier completely from the
power supply. It maintains a low-power
input to an auxiliary sensing circuit.

The switch (7) operates as follows:

O On:
With the switch in this position, the
amplifier remains permanently on, and the
light glows green.

A Auto:
On first switching the subwoofer to Auto,
the amplifier goes into standby mode, and
the light glows red. When an input signal is
detected, the amplifier automatically
becomes fully active and the light 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.

s Standby:
In this position, the amplifier is in
permanent standby, and the light glows
red. If, when set to Auto, the subwoofer
should repeatedly go into standby mode
when playing programme via the LINE IN
socket, try reducing the volume setting on
the subwoofer and restoring the balance by
increasing the subwoofer output of the
processor.

If the subwoofer is to be out of use for an
extended period of time, we recommend
you isolate it from the power supply by
removing the plug from the power socket.

Setting the controls

There are 4 controls to consider:

•

The volume control (VOL) (11)

•

The low-pass frequency
control (Hz) (10)

•

The PHASE switch (9)

•

The EQ (equalisation) switch (8)

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 Active Subwoofer is not a THX®
licensed component, but may be used with
a THX® controller if desired.

•

Set the volume control initially to the
12 o’clock (detent) position.

•

Set the EQ switch initially to position i.

•

Set the PHASE switch initially to +.

•

The setting of the low-pass frequency
control is irrelevant.