Figure 2. XLR to RCA connector for unbalanced operation.

Figure 1. 7050B's amplifier panel, connectors and controls

Figure 3. Recommended distances to

the front wall

.1 output channel of a 5.1-channel discrete surround sound source.

Once all connections have been made, the subwoofer and main loudspeakers are ready to be powered up

Positioning in the room

The placement of the subwoofer in the room affects the overall frequency response and sound level of the system dramatically, as at low frequencies the effects of the room are strong. Even a slight change in the subwoof- er's location can make a marked difference in the frequency balance and often patient and methodical experimentation and testing is needed to find the optimum placement. The placement will affect the phase difference between the main loudspeakers and the sub- woofer and the bass roll-off rate.

First place the subwoofer slightly offset from the center of the front wall. The recommended distance to the wall is less than 60 cm / 24" measured from the subwoofer's driver. This position gives increased acoustic loading (and SPL) due to the proximity of the front wall and floor. Cancellations from the front wall and floor are also avoided. Front wall cancellation for the 85 Hz high pass filtered main speakers can be eliminated by

placing them at least 110 cm / 43" away from the front wall (see Figure 2)

If the frequency balance does not seem right, try moving the subwoofer slightly to the left or right so that different room modes are excited at different levels. Positioning the subwoofer close to a corner will boost the bass level at lower frequencies and may cause asymmetrical spatial imaging

Although the 7050B is magnetically shielded, it may cause colour distortion if placed near to very sensitive video loudspeakers or computer displays. Move the subwoofer further away or try turning the driver side of the subwoofer away from the screen

Minimum clearances to walls

or other objects

Do not cover the driver side of the subwoofer or place the subwoofer so that there is less than 10 cm (4") of free space in front of the grille.

Make sure that the space underneath the subwoofer is clear from obstructions. Thick carpets may block the ventilation clearance needed for cooling the electronics.

The reflex port side (opposite of the connector panel side) should always have a clearance of at least 7,5 centimeters (3") to

any objects to ensure proper functioning of

the reflex port.

Flush mounting the subwoofer

If the subwoofer is flush mounted into a wall or a cabinet, it is important to ensure amplifier cooling and unrestricted airflow from the reflex port. This can be done by making the recess 7,5 centimeters (3") wider than the subwoofer. Place the subwoofer into the right end of the recess with the driver side facing the room. This leaves sufficient 7,5 centimeters (3") of free space on the reflex port side. The height and depth of the recess should not be any bigger than is needed to fit the subwoofer flush with the wall surface.

Sensitivity adjustment

The subwoofer requires input sensitivity alignment to the source to obtain a correctly balanced system. The input sensitivity control is located on the connector panel of the subwoofer. An input voltage of -6 dBu with a -6 dBu input sensitivity setting will produce 100 dB SPL @ 1 m in free field.

Setting the phase control

Incorrect phase alignment between the

main loudspeakers and subwoofer causes