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the half way (12 o’clock) position.
• The setting of the LOW-PASS
FREQUENCY control is irrelevant.
• Set the PHASE switch initially to 0˚.
• Set the LOW-PASS FILTER switch
to OUT.
• Set the EQ switch initially to position A.
See also the section “Fine tuning”.
If you have a THX® controller, ensure that
the subwoofer function is enabled. When
so configured it incorporates all the filtering
and level setting required for the subwoofer
in all modes. For level calibration, the
internal test noise and channel level
controls in the THX® controller should be
used. In all cases the levels should be set
to obtain 75dB SPL (C-weighted) at the
listening position from the controller’s
internal noise test signal.
With other decoders, configure the front
and surround speakers to “large” or “small”
as appropriate before setting the levels.
Use the internal noise test signal and
volume controls of the decoder to set the
levels of all the speakers. Only change the
VOLUME control on the subwoofer if there
is not enough range in the decoder to
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 decoder manual for further details on
how to set the levels.
Use for 2-channel audio
• Set the VOLUME control initially to the
half way (12 o’clock) position.
• Set the LOW-PASS FREQUENCY
initially to 80Hz.
• Set the LOW-PASS FILTER switch
to IN.
• Set the EQ switch initially to position A.
• Set the PHASE switch initially to 0˚.
See also the section “Fine tuning”.
Fine-tuning
There are two settings of the EQ switch.
Position B is optimised to allow the
subwoofer to provide the highest listening
levels, while position A gives greater bass
extension coupled with a tighter sound.
2-channel audio
The optimum settings of the PHASE switch
and the LOW-PASS FREQUENCY control
are inter-related and also dependent on the
low-frequency cut-off characteristic of the
satellite speakers and the relative positions
of all the speakers in the installation.
Set the system up in the preferred position
and play some programme with a steady
bass content. The optimum setting for the
LOW-PASS FREQUENCY depends on
several variables; the bass performance
and power handling of the satellite
speakers, the number of subwoofers used
and their position relative to the satellite
speakers. The range 80 – 90Hz is a good
starting point for the LOW-PASS frequency.
Unless two subwoofers are used to
preserve separate right and left channel
information and are sited close to the
relevant satellite speakers, using a higher
cut-off frequency may compromise the
stereo image and should only be
considered if the bass performance of the
satellite speakers is particularly limited.
At each setting of the cut-off frequency,
listen with the phase switch in both
positions. The correct one is that which
gives the fullest bass and that will depend
on the bass characteristics of your satellite
speakers and the relative distances of the
subwoofer(s) and the satellite speakers to
the listeners. When using more than one
subwoofer, ensure that each one has its
cut-off frequency and phase switch set the
same way.
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.
Home theatre
The situation with home theatre is
somewhat different from 2-channel audio.
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
decoder 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˚.
Decoders 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
that the standard calibration level.
All applications
If you get problems with lumpy 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
decoder output levels or the volume control
on the subwoofer amplifier as appropriate),
but only after setting the phase correctly.
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.
Note: The subwoofer will automatically
shut down if driven excessively. If this
occurs, re-set the subwoofer by turning it
off then on again, using the power on/off
switch on the amplifier panel.
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