Bowers & Wilkins ASW 12CM Using Multiple Subwoofers, Electrical Connections, Before Auditioning

adjusting the volume level of the subwoofer. The more boost gained from the room, the lower the volume can be set and the less hard the subwoofer has to work; but there is a down side. Subwoofers positioned near corners often generate more low-frequency room resonances, making the bass more uneven with frequency. There is no substitute for experiment as all rooms behave differently, so the subwoofer should be tried in a variety of positions before a final decision is made. 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.

If the subwoofer is to be used in a confined space (e.g. built into furniture), the space must be ventilated to allow sufficient air to circulate and cool the unit. Ask your dealer for advice.

The subwoofer is intended to be floor mounted only. It is important to ensure the subwoofer stands firmly on the floor using the spike feet supplied whenever possible. The spike feet are designed to pierce carpet and rest on the floor surface. Initially, screw the lock nuts onto the spikes enough to leave the nuts floating just above the carpet when the spikes are resting on the floor beneath. Screw the spikes fully into the threaded inserts in the base of the cabinet. If the cabinet rocks when placed on the floor, unscrew the two spikes that do not touch the floor until the cabinet rests firmly without rocking. Finally, lock the nuts against the cabinet. It may be more convenient to fit and adjust the spike feet after speaker positioning has been optimised.

If there is no carpet and you wish to avoid scratching the floor surface, use either a protective metal disc (a coin perhaps) between the spike and the floor or use the supplied rubber feet. Fit the rubber feet by screwing one into each of the holes in the underside of the cabinet.

The grille fitted to the front of the subwoofer may be removed if desired. Take care however not to touch the moving parts of the drive unit as damage may result.

Using Multiple Subwoofers

Using multiple subwoofers in a single installation can improve performance in the following ways:

•Maintain stereo separation to the lowest frequencies.

•Smooth out the effects of low frequency room resonances.

•Enable a higher maximum sound output.

In the case of two subwoofers used in a

2-channel audio system, stereo separation will only be improved if each channel has its own subwoofer located close to the appropriate satellite speaker.

Electrical Connections

Disconnect all audio system equipment from the mains until the signal connections have been made and checked. This avoids the risk of damage whilst connections are made or broken. The subwoofer can

accept both line level signals via the RCA Phono sockets (Item 11 in Figure 1) and speaker level signals via the binding posts (Item 12 in Figure 1). Use the following guide to select the appropriate connection method for your installation:

Application: Home Theatre

Subwoofer connected to AV Processor with separate power amplifiers: Figure 2

Subwoofer connected to AV Processor with integrated power amplifiers:

•using line-level inputs: Figure 3

•using speaker level inputs: Figure 4

Note: The subwoofer is always better connected via its line level inputs in home theatre applications.

Application: 2-channel audio

Subwoofer connected to Integrated Amplifier:

•using line-level inputs: Figure 5

•using speaker level inputs: Figure 6

Two Subwoofers connected to Integrated Amplifier:

•using line-level inputs: Figure 7

•using speaker level inputs: Figure 8 Subwoofer connected to Pre/Power Amplifier:

•using line-level input: Figure 9

•using speaker level inputs: Figure 10

Two Subwoofers connected to Pre/Power Amplifier:

•using line-level inputs: Figure 11

•using speaker level inputs: Figure 12

Before Auditioning

Before auditioning your new subwoofer installation and fine-tuning it, double check the connections. Make sure in particular that:

1.The phasing is correct. If the speaker level inputs are used, ensure that the positive terminals on the subwoofer (marked + and coloured red) are connected to the positive output terminals on the amplifier and that the negative terminals on the subwoofer (marked – and coloured black) are connected to the negative output terminals on the amplifier. Incorrect connection can result a confused sound with poor bass.

2.Left to right channels are not confused. Left/right confusion can result for example in orchestral elements appearing in the wrong place in the stereo image, or Home Theatre sound effects not matching the action on screen.

Switching On and Off

Subwoofers are best switched on after any other item and switched off first. The On/Auto/Standby switch (Item 2 in Figure 1) and Status Indicator (Item 1 in Figure 1) operate as follows:

On: With the switch to On, the subwoofer will remain fully active and the indicator will glow green.

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