Bowers & Wilkins Custom Installation Série Manuel Du Propriétaire page 12

(plasterboard) is applied to the wall. It is possible to
install the subwoofer in an existing drywall but the
amount of subsequent wall re-build may make such an
exercise impractical. Carefully consider the implications
of installation in an existing wall before going ahead.
The Back Box supplied with ISW-4 defines its acoustic
loading and must be used for correct operation.
Stage 1: Fitting the Back Box
Drywall (stud wall) construction
Ensure the wall studding is properly prepared so that
there is sufficient clearance for the Back Box and its
cable entry gland. The Back Box is intended to fit
between two adjacent wall studs (battens) on standard
40cm (16 in) spacing. A cross brace (a noggin) should
be positioned directly above the subwoofer. The
subwoofer driver aperture should be located at the
bottom. See Figure 1.
To begin installing the Back Box, loosen the six M5
bolts enough so that the brackets can be adjusted.
Position the right-angle ends of the brackets outboard
of the sides of the Back Box so that they are in
position to line-up with the inside surface of the wall
studs. See Figure 2.
Once the brackets are secured to the Back Box it can
be fitted in the wall. Position the Back Box in the wall
and screw or nail the brackets to the wall studs. Use a
spirit level to ensure the box is vertical in both planes
and tighten the bolts securing brackets to the Back
Box. See Figure 3.
Solid wall construction
If the ISW-4 is to be installed in a solid wall the Back
Box should be built in to the brick or block-work in
a similar manner to a window frame. The brackets,
bolts and washers supplied with the Back Box will not
be required. Care must be taken to avoid the Back
Box rattling against the wall. It should therefore be
wedged in position such as to provide a clear gap all
round. If the Back Box is to be settled onto the lower
course of bricks, use a flexible mastic rather than
cement or mortar. Remember to leave clearance for
the connection gland and cable. The Back Box is not
designed to take the weight of the wall above, so a
suitable lintel must be used. See Figure 4.
Stage 2: Routing the subwoofer cable
With the Back Box fitted in the wall, the cable from the
SA250 amplifier can be routed through the wall and
into the Back Box via its cable entry gland. Pull around
20cm (8 inches) of cable through the gland. Secure the
cable so that it cannot rattle against the studding or
drywall panels and tighten the gland around the cable.
Apply gasket strip around the subwoofer hole in the
back box. See Figure 5.
Stage 3: Plaster finishing the wall
In both drywall and solid wall installations the back
box should be covered with sheetrock (plasterboard)
followed by a plaster skim – on the back as well as the
front if the wall is a single brick thickness. Sheetrock
adjacent to the Back Box should always be fixed with
generous beads of mastic to ensure that no audible
vibration occurs.
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The sheetrock that extends over the front of the Back
Box must have a hole cut accurately to the necessary
profile so that the Wall Frame can be subsequently
fitted in place and secured. Apply the supplied gasket
strip around the subwoofer hole in the back box.
Apply sheetrock over the entire front of the Back Box
securing it with a generous bead of mastic. Using a
small sheetrock saw and, with the cutting template
as a guide, cut out the aperture taking care not to
damage the Back Box. Once the aperture has been
cut the entire wall can be plaster skimmed. See Figure
6. Once the plaster is dry use a vacuum cleaner to
remove completely any dust and debris from inside the
Back Box.
Stage 4: Fitting the Wall Frame
The Wall Frame is secured to the Back Box using the
"dog clamps" on its underside. Rotate the clamps
so that they are oriented inwards and insert the Wall
Frame into the Back Box so that the Wall Frame flange
is flush with the plaster surface. When the Wall Frame
is in position, tighten the dog clamp screws so that
the frame is held securely and flat against the wall.
Tighten opposite dog clamp screws in turn so that the
Wall Frame is pulled flat on to the wall. Ensure that the
connection cable within the Back Box has not been
trapped as the Wall Frame dog clamps are tightened.
See Figure 7.
The wall should be decorated at this stage, with the
supplied Paint Mask fitted over the Back Box aperture.
Use of the Paint Mask is especially important if spray
or roller painting techniques are to be employed.
Stage 5: Fitting the Driver panel
With the Wall Frame secured and the wall decorated,
the Driver Panel can be fitted. Strip 15mm of insulation
from the connecting cable within the back box and
connect it to the spring-loaded connection terminals on
the rear of the Driver Panel. Take care to ensure that
the connection polarity is correct. Connect the positive
cable to the red terminal and the negative cable to the
black terminal. Seat the Driver Panel within the Wall
Frame and secure it with the six bolts supplied. Tighten
opposite Driver Panel bolts in turn so that it is pulled flat
into the Wall Frame. See Figure 8.
Once the Driver Panel is fitted the grille can be push-
fitted in the slot between the panel and the Wall
Frame. If the grille is to be painted, this should be
done before it is fitted. The adhesive B&W badge
supplied can be fitted to the grille if required. Take care
to fit the badge symmetrically.
Stray Magnetic Fields
The subwoofer's drive units create stray magnetic
fields that extend beyond its boundaries. We
recommend you keep magnetically sensitive articles
(CRT television and computer screens, computer
discs, audio and video tapes, swipe cards and the
like) at least 0.5m (20 in) from the speaker. LCD and
plasma screens are not affected by magnetic fields.
Subwoofer Amplifier Installation
The SA250 subwoofer amplifier is intended to be
installed in standard 19 inch equipment racks. It is