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achieve the correct levels.
Inexpensive sound level meters are readily
available from electronics stores and should
be used to calibrate the levels. Refer to
your processor manual for further details on
how to set the levels.
2-channel audio
• Set the VOLUME control initially to the
9 o’clock position.
• Set the LOW-PASS FILTER switch to
IN.
• Set the EQ switch initially to position A.
• Set the PHASE switch initially to 180°.
If you are running the satellite speakers full
range (figs 6, 7, 10, 11).
• Set the LOW-PASS FILTER frequency
to the -6dB cut-off frequency of your
satellite speakers.
Both -3dB and -6dB figures are to be
found in the specification of each B&W
speaker model. However, if the
manufacturer of the satellite speakers does
not quote a -6dB frequency, but only a -
3dB frequency, the optimum setting for the
LOW-PASS FILTER frequency control will
be between 0.6 and 0.9 times the -3dB
frequency, depending on the roll-off
alignment. The more gradual the roll-off
rate of the satellite speakers, the lower the
frequency should be set.
If you are running the satellite speakers
high-passed (figs 8, 9, 12, 13).
• Set the LOW-PASS FILTER frequency
initially to 80Hz.
See also the section "Fine tuning".
Fine-tuning
Home theatre
With home theatre the subwoofer (LFE)
signal is a separate channel rather than an
extension of the signal to the satellite
speakers. The LOW-PASS FILTER is
switched out, because the processor
provides all the filtering for any speakers
set to "small". However, the position of the
phase switch must still be assessed.
Normally the phase will be set to 0°, but if
the subwoofer is positioned at a distance
significantly different from the other
speakers, or the power amplifier driving the
other speakers happens to invert the
signal, the 180° position may be preferable.
Listen with the switch in both positions and
choose the one that gives the fullest sound.
If there is little difference, leave the switch
at 0°.
Surround sound processors normally have
a calibrated noise signal that can be used
to set the relative levels of all the speakers,
making the task somewhat more
straightforward than for 2-channel audio.
However, do not be afraid to alter the
settings to your personal preference. It is all
too easy to get carried away with the
capabilities of the subwoofer, especially
with some special low-frequency effects.
Often a more realistic portrayal, and one
more satisfying in the long term, is to be
had by setting the subwoofer level lower
than the standard calibration level.
2-channel audio
The optimum settings of the PHASE switch
and the LOW-PASS FILTER frequency
control are inter-related and also dependent
on the low-frequency cut-off characteristic
of the satellite speaker. However, the
settings recommended above for the LOW-
PASS FILTER frequency and PHASE have
been chosen to add well to most bass
alignments, whether closed-box or vented-
box (reflex), with -6dB frequencies within
the adjustment range of the subwoofer.
If feeding the satellite speakers via the
high-pass filter of the subwoofer, the
frequency will need to be set lower than the
initial value of 80Hz if the -3dB frequency of
the satellite speakers is lower than 80Hz
and higher if above.
Set the system up in the preferred position
and play some programme with a steady
bass content.
Using the initial settings guide, first check
the setting of the PHASE switch. Choose
the position that gives the fullest sound.
Normally the recommended position will be
optimum, but may not be in certain
circumstances, such as if you are using line
level connections and the power amplifiers
feeding the satellite speakers invert the
signal, or if the subwoofers are not placed
close to the satellite speakers.
Next, set the loudness of the subwoofer
relative to the satellite systems to your
liking. Use a wide variety of programme
material to get an average setting. One that
sounds impressive on one piece may
sound overpowering on another. Listen at
realistic levels as the perception of balance
varies with sound level.
Finally, adjust the LOW-PASS FILTER
frequency to give the smoothest transition
between the subwoofer and satellite
speakers. This is probably the most difficult
to optimise.
All applications
The EQ switch alters the bass roll-off
alignment. The bass you hear is a
combination of the subwoofer plus the
effects of the room and you should choose
the position that best complements your
room and the position of the subwoofer.
Position A gives a drier alignment, more
suited to placing the subwoofer in a corner
or compensating a boomy room. Position B
is more suited to a dry room acoustic and
use away from a corner.
If you get problems with uneven bass – if
certain bass notes are exaggerated more
than others – then you probably have a
room interface problem and it is worth
experimenting with the placement of the
subwoofer. What may seem like small
changes in position – 15cm (6in) or so –
can have a profound effect on the sound.
Try raising the subwoofer clear of the floor
as well as lateral movement. The use of
multiple subwoofers can smooth the effects
of room resonances, as each subwoofer
will tend to excite resonances at different
frequencies. If you alter the relative
distances from the subwoofer(s) and
satellite speakers to the listeners
appreciably, reassess the phase switch
setting. You should also check the level
setting of the subwoofer (using either the
processor output levels or the volume
control on the subwoofer amplifier as
appropriate), but only after setting the
phase correctly.
When using more than one subwoofer,
ensure that each one has its LOW-PASS
FILTER frequency and PHASE set the same
way.
Taking care of the subwoofer
The cabinet of the subwoofer may be
cleaned by dusting with a dry cloth. If you
wish to use an aerosol cleaning spray, do
not spray directly on the cabinet; spray
onto the cloth. Remove the grille first so
that the cloth does not become stained,
but be careful not to disturb the drive unit.
The grille itself may be cleaned using a soft
brush.
Do not use the subwoofer as a table. When
in use, objects left on top of the subwoofer
are liable to rattle. In particular, avoid the
risk of liquids being spilled (eg from drinks
or vases of flowers).
If the system is taken out of use for a long
period, disconnect the subwoofer from the
power supply.
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