Orban OPTIMOD-FM 5500 Operation Manual page 172

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OPERATION
dense and fatiguing when the radio is played loudly.
Bx THR ("Band x Compression Threshold") controls set the compression threshold in
each band, in units of dB below the final clipper threshold. We recommend making
small changes around the factory settings to avoid changing the range over which
the MB CLIPPING control operates. These controls will affect the spectral balance of
the processing above threshold, but are also risky because they can strongly affect
the amount of distortion produced by the back-end clipping system.
MB GATE ("Multiband Gate Threshold") control determines the lowest input level
that will be recognized as program by OPTIMOD-FM; lower levels are considered to
be noise or background sounds and cause the AGC or multiband compressor to gate,
effectively freezing gain to prevent noise breathing.
There are two independent gating circuits in the 5500. The first affects the AGC and
the second affects the multiband compressor. Each has its own threshold control.
The 5500's input drives the AGC gate detector; the output of the 5500's AGC drives
the MB gate detector.
The multiband compressor gate causes the gain reduction in bands 2 and 3 of the
multiband compressor to move quickly to the average gain reduction occurring in
those bands when the gate first turns on. This prevents obvious midrange coloration
under gated conditions, because bands 2 and 3 have the same gain.
The gate also independently freezes the gain of the two highest frequency bands
(forcing the gain of the highest frequency band to be identical to its lower
neighbor), and independently sets the gain of the lowest frequency band according
to the setting of the DJ B
out introducing obvious coloration, the gating smoothly preserves the average
overall frequency response "tilt" of the multiband compressor, broadly maintaining
the "automatic equalization" curve it generates for a given piece of program mate-
rial.
If the control is turned
MB GATE
tion screen) is disabled.
MB LIM DR ("Multiband Limiter Drive") sets the drive level to the multiband distor-
tion controlling processing that precedes the final clipping section. The distortion-
controlling section uses a combination of distortion-cancelled clipping and look-
ahead processing to anticipate and prevent excessive clipping distortion in the final
clipper.
Like any other dynamics processing, the distortion-controlling section can produce
artifacts of its own when overdriven. These artifacts can include loss of definition,
smeared high frequencies, a sound similar to excessive compression, and, when op-
erated at extreme settings, audible intermodulation distortion. You can adjust the
MB LIM DR control to prevent such artifacts or to use them for coloration in "highly
processed" formats.
MB LIM THR ("Multiband Limit Threshold") sets the threshold of the clipping dis-
tortion controller with reference to the threshold of the final clipper, in dB.
boost control (in the Equalization screen). Thus, with-
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, the
O DJ B
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ORBAN MODEL 5500
control (in the Equaliza-
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