Genelec 7070A - Manual (Page 4)

Figure 4. The effect of phase difference between the subwoofer and the main monitors
Although the 7060A, 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 amplifi ers 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 refl ex port side (opposite of the ampli-
fi er panel side) should always have a clear-
ance of at least 7,5 centimeters (3") to any
objects to ensure proper functioning of the
refl ex port.
Flush mounting the subwoofer
If the subwoofer is fl ush mounted into a wall
or a cabinet, it is important to ensure unre-
stricted airfl ow from the refl ex port and ampli-
fi er 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 suffi cient 7,5 centime-
ters (3") of free space on the refl ex port side.
The height and depth of the recess should
not be any bigger than those needed to fi t
the subwoofer fl ush 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 amplifi er 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 fi eld. 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 amplifi er
panel. Table 1 provides some suggestions
for the "Bass Roll-Off" switch settings. When
both roll-off switches are set to "OFF", a fl at
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 7060A, 7070A and 7071A subwoof-
ers are equipped with a built-in 85 Hz fre-
quency test tone generator for easy phase
alignment. The test tone generator is con-
nected to the subwoofer's "FRONT CENTER
OUT" channel only. In a stereo system it is
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
Gen 7060A+7070A+7071A 22.5.2002, 11:04 4
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