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If you are using two subwoofers for stereo audio,
stereo separation is improved if each channel
has its own subwoofer, providing each one is
sited close to the relevant satellite speaker.
If the subwoofers cannot be ideally sited, or if
you are using a dedicated subwoofer output
from a decoder, connect the second subwoofer
from the first. If using a decoder, use only one
input channel. For two channel audio, both input
channels should be used.
Double check the connections
Before auditioning the sound quality of your new
installation and fine tuning it, double check the
connections. All too often, users complain that
they cannot get a decent sound however they set
the controls, only to discover something has been
wrongly connected. Make sure that:
• The phasing is correct – there should be no
positive to negative connections (this applies
only to speaker level interconnects). If
something is out of phase you may get a fuzzy
sound with an imprecise and floating image,
a lack of bass or a combination of the two.
• There are no left to right mix-ups – this can
result, for example, in the orchestra being the
wrong way round or, more disastrously, sounds
on your home theatre going in the opposite
direction to the action on the screen.
Switching on and off
We recommend that you switch the subwoofer
on before any power amplifiers receiving signals
from the subwoofer. Similarly, when switching
off, switch the subwoofer off last.
On first switching the subwoofer on, the amplifier
goes into standby mode and the light above the
on/auto/off switch glows red. When an input
signal is detected, the amplifier automatically
becomes fully active and the light glows green.
After a period of about 5 minutes without an
input signal, the amplifier automatically reverts
to standby mode.
Setting the controls
There are three controls to consider:
• The LOW-PASS filter frequency
• The VOLUME control
• The PHASE switch
The optimum settings depend on the other
equipment used with the subwoofer. If using
more than one subwoofer, make sure the controls
on each one are set the same.
Use with THX
®
controllers (including THX
controllers set in non-THX mode)
The ASW2000 is not an THX licensed
component, but may be used with a THX
controller if desired.
• Set the LOW-PASS filter frequency to
maximum.
• Set the VOLUME control to the half-way
(12 o’clock) position (this is a standard THX
pre-set level)
• Set the PHASE switch initially to 0°, then see
the section below on fine tuning.
Ensure that the subwoofer function on the THX
controller 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 so as
to obtain 75db spl (C-weighted) at the listening
position from the controller’s internal noise test
signal. Refer to your controller manual for further
details as to how to set the levels. Inexpensive
sound level meters are readily available from
electronics stores and should be used to
calibrate the levels.
Use with other home theatre decoders
•
If the decoder has a dedicated subwoofer
output and an internal low-pass filter for the
subwoofer having a slope of 2nd-order
(12db/octave) or greater, set the LOW-PASS
filter frequency to maximum, otherwise set it
initially to 80Hz.
• Set the volume control initially to the half-way
(12 o’clock) position, then see the section
below on fine tuning.
•
Set the phase switch initially to 0°, then see
the section below on fine tuning.
Use for stereo audio
• Set the LOW-PASS filter initially to 80hz then
see the section below on fine tuning.
• Set the VOLUME control initially to the half way
(12 o’clock) position, then see the section
below on fine tuning.
• Set the PHASE switch initially to 0°, then see
the section below on fine tuning.
Fine tuning
The optimum settings of the PHASE switch and
the LOW-PASS filter frequency 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 cut-off
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.
If at any time you make changes to the
amplification of the system such that you change
from speaker to line level connections to the
subwoofer, it is worth checking the phase setting
again, as the speaker level and line level
high-pass filter phase characteristics of the
subwoofer are different.
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.
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.