OPTIMOD SURROUND PROCESSOR OPERATION
3-61
ral upper midrange boost. The gain of band 5 is further affected by the BAND 4>5
COUPLING control.
The C
OUPLING controls use an “OR” algorithm: the final gain reduction in a given
band is the higher of (1) the gain reduction that would have been produced in that
band with no coupling, OR (2) the gain reduction in the adjacent coupled band mul-
tiplied by the setting of the C
OUPLING control.
For example, assume that Band 4 would produce 10 dB of gain reduction with no
B3>B4 coupling. If the B
AND 3>4 COUPLING control is set to 50%, Band 3 will not af-
fect Band 4’s gain reduction unless Band 4 is producing more than 20 dB of gain re-
duction. At this point, every 2 dB increase in Band 4’s gain reduction will cause a 1
dB increase in Band 3’s gain reduction.
B4>B5 Couple
(“Band 4>5 Coupling”) controls the extent to which the gain of
band 5 (6.2 kHz and above) is determined by and follows the gain of band 4.
The sum of the high frequency limiter control signal and the output of the B
AND 4>5
COUPLING control determines the gain reduction in band 5. The BAND 4>5 COUPLING
control receives the independent left and right band 4 gain control signal. Range is
0 to 100% coupling.
B3>B2 Couple
and B2>B3 Couple controls determine the extent to which the
gains of bands 2 and 3 track each other.
When combined with the other coupling controls, these controls can adjust the mul-
tiband processing to be anything from fully independent operation to quasi-
wideband processing.
B2>B1 Couple
control determines the extent to which the gain of band 1 (below
100Hz or 200Hz, depending on crossover setting) is determined by and follows the
gain of band 2 (centered at 400Hz). Set towards 100% (fully coupled), it reduces the
amount of dynamic bass boost, preventing unnatural bass boost. Set towards 0%
(independent), it permits frequencies below 100Hz (the “slam” region) to have
maximum impact in modern rock, urban, dance, rap, and other music where bass
punch is crucial. Accordingly, it can be useful in music video oriented formats.
Bx Out
(“Band x Output Mix”) controls determine the relative balance of the bands
in the multiband compressor. Because these controls mix after the band compres-
sors, they do not affect the compressors’ gain reductions and can be used as a
graphic equalizer to fine-tune the spectral balance of the program material over a
±3 dB range.
Their range has been purposely limited because the only gain control element after
these controls is the back-end clipping system (including the multiband clip-
per/distortion controller), which can produce considerable audible distortion if over-
driven. The thresholds of the individual compressors have been tuned to prevent
audible distortion with almost any program material. Large changes in the fre-
quency balance of the compressor outputs will change this tuning, leaving the 8685
more vulnerable to unexpected audible distortion with certain program material.
Therefore, you should make large changes in EQ with the bass and parametric
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