Bowers & Wilkins ASW CDM Positioning the subwoofer, Electrical connections, Switching on and off

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:

aOne or more subwoofers with output combined into a single mono signal – fig. 4

bTwo 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

4