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3-62
OPERATION
Their range has been purposely limited because the only gain control element after
these controls is the look-ahead limiter, which can produce pumping or distortion if
overdriven. The thresholds of the individual compressors have been tuned to pre-
vent audible distortion with almost any program material. Large changes in the fre-
quency balance of the compressor outputs will change this tuning, leaving
OPTIMOD-PC more vulnerable to unexpected audible distortion with certain pro-
gram material.
You can also get a similar effect by adjusting the compression threshold of the indi-
vidual bands. This is comparably risky with reference to look-ahead limiter overload,
but unlike the MB B
AND
frequency response when a given band is below threshold and is thus producing no
gain reduction.
B1-B5 On/Off switches allow you to mute any combination of bands in the five-
band compressor and permit you to "solo" any individual band.
B1-B5 Attack (Time); Speech B1-B5 Attack controls set the speed with which the
gain reduction in each band responds to level changes at the input to a given band's
compressor for music and speech respectively, following OPTIMOD-PC's automatic
speech/music detector. These controls are risky and difficult to adjust appropriately.
They affect the sound of the processor in many subtle ways. The main trade-off is
"punch" (achieved with slower attack times) versus distortion and/or pumping pro-
duced in the look-ahead limiter (because slower attack times increase overshoots
that the look-ahead limit must eliminate). The results are strongly program-
dependent and must be verified with listening tests to a wide variety of program
material.
Because there are separate controls for music and speech (page 3-6), you can set at-
tack times faster for speech (to minimize look-ahead limiter artifacts) and slower for
music (to maximize punch and transient definition).
The A
time controls are calibrated in arbitrary units that very approximately
TTACK
correspond to milliseconds. Higher numbers correspond to slower attacks.
Limiter Attack controls allow you to set the limiter attack anywhere from 0 to
100% of normal in the Five-Band compressors, each of whose gain reduction has a
fast-release (limiter) and slow-release (compressor) component. Because the limiter
and compressor characteristics interact, you will usually get best audible results
when you set these controls in the range of 70% to 100%. Below 70%, you will usu-
ally hear pumping because the compressor function is trying to create some of the
gain reduction that the faster limiting function would have otherwise achieved. If
you hear pumping in a band and you still wish to adjust the limiter attack to a low
setting, you can sometimes ameliorate or eliminate the pumping by slowing down
the compressor attack time in that band.
These controls have nothing to do with the final look-ahead limiter.
Delta Release controls are differential controls. They allow you to vary the release
time in any band of the Five-Band compressor/limiter by setting an offset between
the M
R
ULTIBAND
ELEASE
M
controls, the threshold adjustments do not affect the
IX
setting and the actual release time you achieve in a given
ORBAN MODEL 1101
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