Orban OPTIMOD-FM 8500S Operating Manual page 220

3-56
OPERATION
can go without causing unacceptable listener fatigue. However, this sound may
be useful for stations that are ordinarily heard very softly in the background be-
cause it improves intelligibility under these quiet listening conditions. Stations
that are usually played louder will probably prefer one of the slower release
times, where the multiband compressor takes more gain reduction and where
the AGC is operated slowly for gentle gain riding only. These slower sounds are
less consistent than those produced by the F
more of the source's frequency balance, making the sound less dense and fatigu-
ing when the radio is played loudly.
The S
MB R
PEECH
8500S automatically detects speech (page 3-63). You may wish to set the S
control faster for speech (to maximize smoothness and uniformity)
MB R
ELEASE
and slower on music (to prevent excessive build-up of density).
MB Gate Thresh (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 8500S. The first affects the AGC
and the second affects the multiband compressor. Each has its own threshold con-
trol.
V2.0 software sets the multiband compressor's gating threshold with respect to the
signal driving the multiband compressor/limiter, which follows the AGC. Meanwhile,
the AGC gating threshold remains set with respect to the AGC's input, as it was in
V1.x software. Driving the MB gate detector after the AGC allows the AGC to do its
work of slowly correcting the drive level to later processing, including the multiband
gate.
When the AGC produces 10 dB of gain reduction, the calibration of the MB GATE
control in V2.x software is the same as it was in V1.x software. When upgrading
from V1.x to V2.x, it should thus be unnecessary to change the MB GATE setting in
User Presets unless the AGC's nominal gain reduction is significantly different from
10 dB.
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.
control overrides the MB R
ELEASE
boost control (in the Equalization screen). Thus, with-
ASS
ORBAN MODEL 8500S
setting. Using S
AST LOW
control when the
ELEASE
preserves
PEECH