channel amplifier back on to restore normal system operation. When you wish to
restore Autobalance operation, push the AUTO button (located between the left and
right buttons) to disengage manual balance.
OUTPUT LEVEL CALIBRATION
The SP MK II provides individual channel output level controls. These allow you to
compensate for differences in amplifier and speaker sensitivities and for placement
variations from installation to installation. These set-and-forget adjustments are essen-
tial for reproducing proper soundstaging and image localization. These controls are
located on the rear panel of the SP MK II just above the audio output jacks.
Adjusting the output levels is done after completing the input level adjustments. Once
this is completed, system volume changes are made using the up/down buttons on the
infrared remote control.
The best way to adjust the output level controls is by using a dB Sound Pressure Level
(SPL) meter in conjunction with the internal bandwidth-limited pink noise generator in
the SP MK II. The goal is to set the volume at the primary listening position to read 75
dB SPL
(C-weighted, slow mode)
from each speaker in sequence, using the individ-
ual output level controls. You should use the meter pointing straight up towards the
ceiling.
The “average” setting of the individual output level controls should be ideally near the
midrange of their rotation. The simplest way to achieve this is to set the Master Volume
at 0 REF on the liquid crystal display and then adjust each individual channel output
trim control (located on the rear panel) until a 75 dB SPL is achieved. The Master 0
REF setting becomes the calibrated playback setting for any software which has been
dubbed carefully, with proper attention to soundtrack levels. Some adjustments to the
input level and input balance controls may be required to compensate for soundtracks
with different levels and channel balance.
In the absence of a dB SPL meter, it is possible to set the output level controls by ear.
Use the built-in test noise generator in the SP MK II to adjust all volumes to sound the
same as they cycle around the various speakers. The test signal is bandwidth-limited
pink noise to minimize the problem of timbre shifts influencing the setting of levels.
Even so, using non-THX-certified loudspeakers may make this more difficult to judge,
due to variations in spectral balance between the various speakers—especially mis-
matched left/right front and center speakers. Simply get as close as you can! The sys-
tem should then be reasonably well balanced, although of course it is not actually cali-
brated for precise playback levels.
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