Optimod-Surround 8685 V1.0 Operating Manual - Orban

3-62
OPERATION ORBAN MODEL 8685
equalizers and the HF enhancer, because these are located before the compressors.
The compressors will thus protect the system from unusual overloads caused the
chosen equalization. Use the multiband mix controls only for fine-tuning.
You can also get a similar effect by adjusting the compression threshold of the individual
bands. This is comparably risky with reference to clipper overload, but unlike
the MB BAND MIX controls, the threshold adjustments do not affect the frequency response
when a given band is below threshold and is thus producing no gain reduction.
Advanced Five-Band Controls
B1-B5 Attack (Time); Speech B1-B5 Attack (2.0); Center B1-B5 Attack (surround)
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. These controls 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 produced in
the look-ahead limiter (because slower attack times increase overshoots that the
look-ahead limiter must eliminate). The results are strongly program-dependent and
must be verified with listening tests to a wide variety of program material.
The ATTACK time controls are calibrated in arbitrary units that very approximately
correspond to milliseconds. Higher numbers correspond to slower attacks.
In the 2.0 processing, there are separate controls for music and speech (page 3-6), so
you can set attack times faster for speech (to minimize look-ahead limiter artifacts)
and slower for music (to maximize punch and transient definition). In the surround
processing, there are separate controls for the center channel.
B1-B5 Limiter Attack controls allow you to set the limiter attack anywhere from 0
to 100% of normal in the Five-Band compressor/limiters. 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 usually
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.
Setting these controls to around 50% can increase punch when you are using low
compression ratios with small amounts of gain reduction.
B1-B5 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 MULTIBAND RELEASE setting and the actual release time you achieve in a
given band. For example, if you set the MULTIBAND RELEASE control to medium-fast
and the BAND 3 DELTA GR control to –2, then the band 3 release time will be the
same as if you had set the MULTIBAND RELEASE control to medium and set the BAND 3
DELTA GR control to 0. Thus, your settings automatically track any changes you make
in the MULTIBAND RELEASE control. In our example, the release time in band 3 will always
be two “click stops” slower than the setting of the MULTIBAND RELEASE control.