Orban OPTIMOD-FM 8700, Operating Manual

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OPTIMOD-FM DIGITAL OPERATION
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tigue.
Release in the two-band compressor automatically becomes faster as
more gain reduction is applied (up to about 10 dB). This makes the pro-
gram progressively denser, creating a sense of increasing loudness alt-
hough peaks are not actually increasing. If the gain-riding AGC is defeat-
ed (with the
AGC on/off control), you can use this characteristic to pre-
serve some feeling of dynamic range. Once 10 dB of gain reduction is ex-
ceeded, full loudness is achieved—no further increase in short-term den-
sity occurs as more gain reduction is applied. This avoids the unnatural,
fatiguing sound often produced by processors at high gain reduction lev-
els and makes OPTIMOD-FM remarkably resistant to operator gain-riding
errors.
2B Gate Thresh (Threshold) control determines the lowest input level that OPTIMOD-
FM recognizes as program; lower levels are considered to be noise or background
sounds and will cause the AGC or two-band compressor to gate, effectively freezing
gain to prevent noise breathing.
There are two independent gating circuits in the 8700i. The first affects the AGC and
the second affects the two-band compressor. Each has its own threshold control.
The two-band gain reduction will eventually recover to 0 dB and the AGC gain re-
duction will eventually recover to –10 dB even when their compressor gates are gat-
ed. However, recovery is slow enough to be imperceptible. This avoids OPTIMOD-
FM’s getting stuck with a large amount of gain reduction on a long, low-level musi-
cal passage immediately following a loud passage.
It is common to set the
2B G
ATE
T
HRESH
control to –40. Higher settings are primarily
useful for radio drama, outside sports broadcasts, and other non-musical program-
ming that contain ambiance, low-level crowd noise, and the like. Slightly higher set-
tings may increase the musicality of the compression by slowing down recovery on
moderate-level to low-level musical passages. When such passages cause the gate to
cycle on and off, recovery time will be slowed down by the ratio of the “on-time” to
the “off time.” This effectively slows down the release time as the input gets pro-
gressively quieter, thus preserving musical values in material with wide dynamic
range (classical music for example).
2B Bass Coupling control is used to set the balance between bass and the rest of the
frequency spectrum.
The two-band compressor processes audio in a master band for all audio above ap-
proximately 200 Hz and a bass band for audio below approximately 200 Hz. The
2B
B
ASS
C
OUPLING
control determines how closely the on-air balance of material below
200 Hz matches that of the program material above 200 Hz.
Settings toward 100% (wideband) make the output sound most like the input. Be-
cause setting the
2B B
ASS
C
OUPLING
control at 100% will sometimes cause bass loss,
the most accurate frequency balance will often be obtained with this control set be-
tween 70% and 90%. The optimum setting depends on the amount of gain reduc-
tion applied. Adjust the
2B B
ASS
C
OUPLING
control until the band 1 and band 2 Gain
Reduction meters track as closely as possible.