symmetrically and at an equal distance from
the listening position.
If the frequency balance is not 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. If you
are using two subwoofers, try placing them
asymmetrically relative to the side walls.
Sometimes moving the subwoofers apart
into the front corners helps with problematic
rear wall reflections and the loss of mutual
coupling is compensated by the bass boost
caused by corner positioning.
Although the HTS6 subwoofer is magneti-
cally shielded, they may cause some picture
distortion if placed near very sensitive video
monitors or computer displays.
Minimum clearances to walls
or other objects
The power amplifiers are attached to the
lower part of the aluminium grilles, which
function as a heatsink. Do not cover the
grilles or place the subwoofer so that there is
less than 10 centimeters (4") of free space in
front of the grilles.
The reflex port and connector panel should
always have a clearance of at least 20 cen-
timeters (8") to any objects to ensure proper
function of the port and cooling for the elec-
tronics attached to the connector panel.
Flush mounting the subwoofer
If the subwoofer is flush mounted into a
wall or a cabinet, it is important to ensure
unrestricted airflow from the reflex port
and cooling for the electronic components.
This can be done by making the recess 20
centimeters (8") wider than the subwoofer.
Place the subwoofer into the right end of
the recess with the drivers' side facing the
room. This leaves sufficient 20 centimeters
(8") of free space on the connector panel and
reflex port side. The height and depth of the
recess should not be any bigger than those
needed to fit the subwoofer flush with the
wall surface.
Setting the input sensitivity
The subwoofer requires input sensitivity
alignment to the source to obtain a correctly
balanced system. The input sensitivity con-
trol 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 @ 1m in free field. To obtain a
110 dB SPL output an input voltage of +10
dBu is required when the input sensitivity is
set to 0 dBu.
Setting the Bass Roll-Off
switches
The acoustic response of the subwoofer may
have to be matched to the characteristics of
the room and the positioning in which it will
be used. To adjust the subwoofer to match
these characteristics use the ''Bass Roll-Off'
control switches located on the connector
panel. Table 1 provides some suggestions
for the "Bass Roll-Off" switch settings. When
all roll-off switches are set to "OFF", a flat
anechoic response is obtained.
Setting the phase control
Incorrect phase alignment between main
monitors and subwoofer causes a drop in
the frequency response of the whole system
at the crossover frequency. The graphs on
the following page (Fig. 4) show the effect of
phase difference to the frequency response.
The phase difference between the main
Figure 1. HTS6's connector panel, connectors and controls.
Figure 2. XLR to RCA connector for
unbalanced operation.
Table 1. Suggested Bass Roll-Off settings
Subwoofer placement Bass Roll-Off
setting
Near to a wall -2 dB
In a corner -6 dB
Flush mounted -2 dB