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Figure 4. The effect of phase difference between the subwoofer and the main monitors
Although the 7060B, 7070A and 7071A
subwoofers are magnetically shielded, they
may cause some picture distortion if placed
near very sensitive video monitors or com-
puter displays. Move the subwoofer further
away or try turning the driver side of the
subwoofer away from the screen.
Minimum clearances to walls
or other objects
The power amplifiers are attached to the
lower part of the aluminium grille, which func-
tions as a heatsink. Do not cover the grille
or place the subwoofer so that there is less
than 10 centimeters (4") of free space in front
of the grille.
Make sure that the space underneath the
subwoofer is clear from obstructions. Thick
carpets may block the ventilation clearance
needed for cooling the electronics' box.
The reflex port side (opposite of the con-
nector panel side) should always have a
clearance of at least 7,5 centimeters (3") to
any objects to ensure proper functioning of
the reflex port.
Flush mounting the subwoofer
If the subwoofer is flush mounted into a wall
or a cabinet, it is important to ensure unre-
stricted airflow from the reflex port and ampli-
fier cooling. This can be done by making the
recess 7,5 centimeters (3") wider than the
subwoofer. Place the subwoofer into the right
end of the recess with the driver side facing
the room. This leaves sufficient 7,5 centime-
ters (3") of free space on the 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
both 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 above
(Fig. 4) show the effect of phase difference
to the frequency response.
The phase difference between the main
monitors and subwoofer at the listening posi-
tion is dependent upon the position of the
subwoofer, so the phase adjustment should
be done only after the preferred position is
found. Acoustic measuring equipment is
required for accurate system alignment. If
this equipment is not available, the following
coarse phase matching can be applied.
Coarse phase adjustment
method
Genelec 7060B, 7070A and 7071A
subwoofers are equipped with a built-in 85
Hz frequency test tone generator for easy
phase alignment. The test tone generator
is connected to the subwoofer's "FRONT
CENTER OUT" channel only. In a stereo
Phase Difference: 0°
85 Hz
Phase Difference: 180°
85 Hz
Phase Difference: 270°
85 Hz
Phase Difference: 90°
85 Hz
Figure 5. Flush mounting the subwoofer.
Note the clearance needed on the reflex
port side.
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