Bowers & Wilkins ASW 2500: Switching on and off

necessary for 2-channel audio, split the signal

the controls, only to discover something has been

more than one subwoofer, ensure the controls on

into low bass and higher frequencies and feed

wrongly connected. Make sure that:

each one are set the same.

the latter back out to the satellite speakers. Left

• The phasing is correct – there should be no

Use with home theatre decoders

and right channel inputs may be combined into

positive to negative connections to the

a single mono low bass feed to the subwoofer

The ASW™2500 is not a THX

®

licensed

satellite speakers. If something is out of

drive unit if required.

component, but may be used with a THX

®

phase you may get a fuzzy sound with an

controller if desired.

The subwoofer will input and output line-level

imprecise and floating image, a lack of bass

signals via the RCA Phono sockets located on

or a combination of the two.

• Set the decoder VOLUME control to the half

the back panel.

way (12 o’clock) position.

• There are no left to right mix-ups – this can

Use the following table to select the correct

result, for example, in the orchestra being the

• The setting of the LOW-PASS FREQUENCY

wiring method for your installation:

wrong way round or, more disastrously,

control is irrelevant.

sounds on your Home Theatre going in the

Application: Home Theatre

• Set the PHASE switch initially to 0˚.

opposite direction to the action on the

The subwoofer may be used with any decoder

screen.

• Set the LOW-PASS FILTER switch to OUT.

that has a line-level subwoofer output (normally

• Set the EQ switch initially to position A.

from an RCA Phono socket). Most decoders with

integral power amplifiers still output the

Switching on and off

See also the section “Fine tuning”.

subwoofer or Low-Frequency Effects (LFE) signal

We recommend that you switch the subwoofer

If you have a THX

®

controller, ensure that the

at line level.

on before any power amplifiers receiving signals

subwoofer function is enabled. When so

• Decoder with one or more subwoofers –

from the subwoofer. Similarly, when switching

configured it incorporates all the filtering and

fig. 3

off, switch the subwoofer off last.

level setting required for the subwoofer in all

modes. For level calibration, the internal test

Application: 2-channel audio

The on/auto/standby switch (9) at the top right

noise and channel level controls in the THX

®

of the amplifier panel does not isolate the

Separate pre- & power amplifiers:

controller should be used. In all cases the levels

amplifier completely from the power supply. It

should be set to obtain 75dB SPL (C-weighted)

a One or more subwoofers with output

maintains a low-power input to an auxiliary

at the listening position from the controller’s

combined into a single mono signal – fig. 4

sensing circuit. The 230V version of the amplifier

internal noise test signal.

has an additional switch (13) that completely

b Two subwoofers with separate left and right

isolates the power supply. To isolate other

With other decoders, configure the front and

signal – fig. 5

versions, either switch off at the wall outlet or

surround speakers to “large” or “small” as

The ASW™2500 is not suitable for use with 2-

disconnect the power cord from the amplifier.

appropriate before setting the levels. Use the

channel integrated pre/power amplifiers, unless

We recommend you isolate the subwoofer from

internal noise test signal and volume controls of

they feature a line level output from the pre-

the power supply if it is to be out of use for

the decoder to set the levels of all the speakers.

amplifier.

extended periods of time.

Only change the VOLUME control on the

subwoofer if there is not enough range in the

The switch (9) operates as follows:

decoder to achieve the correct levels.

Using more than one subwoofer

On:

Inexpensive sound level meters are readily

With the switch in this position, the amplifier

Using more than one unit in a single installation

available from electronics stores and should be

remains permanently on, and the light glows

can improve performance in the following ways:

used to calibrate the levels. Refer to your

green.

decoder manual for further details on how to set

• Maintain stereo separation to the lowest

Auto:

the levels.

frequencies.

On first switching the subwoofer to Auto, the

Use for 2-channel audio

• Cope with larger listening rooms.

amplifier becomes fully active and the light (10)

above the on/auto/standby switch glows green.

• Set the VOLUME control initially to the half

• Enable greater maximum sound output –

After a period of about 5 minutes without an

way (12 o’clock) position.

often useful for effectively reproducing

input signal, the amplifier automatically reverts to

special effects in Home Theatre applications.

• Set the LOW-PASS FREQUENCY initially to

standby mode, and the light glows red. When

80Hz.

• Smooth out the effects of low-frequency room

an input signal is detected, the amplifier

resonances.

automatically becomes fully active and the light

• Set the LOW-PASS FILTER switch to IN.

glows green.

If you are using two subwoofers for 2-channel

• Set the EQ switch initially to position B.

audio, separation is improved if each channel

Standby:

• Set the PHASE switch initially to 0˚.

has its own subwoofer, providing each one is

In this position, the amplifier is in permanent

placed close to the relevant satellite speaker.

standby, and the light glows red.

See also the section “Fine tuning”.

Only use the mono connection of figure 4 if you

cannot place each subwoofer close to its satellite

speaker.

Setting the controls

Fine-tuning

There are 5 controls to consider:

There are two settings of the EQ switch. Position

A is optimised to allow the subwoofer to provide

Double-check the connections

• The VOLUME control (4)

the highest listening levels, while position B gives

ENSURE THAT THE VOLTAGE INDICATED ON

• The LOW-PASS FREQUENCY control (5)

greater bass extension coupled with a tighter

THE AMPLIFIER PANEL MATCHES THAT OF THE

sound.

• The PHASE switch (6)

POWER SUPPLY.

2-channel audio

• The LOW-PASS FILTER switch (7)

Before auditioning the sound quality of your new

The optimum settings of the PHASE switch and

installation and fine-tuning it, double-check the

• The EQ (equalisation) switch (8)

the LOW-PASS FREQUENCY control are inter-

connections. All too often, users complain that

The optimum settings depend on the other

related and also dependent on the low-frequency

they cannot get a decent sound however they set

equipment used with the subwoofer. If using

cut-off characteristic of the satellite speakers and

3