3-38
OPERATION
ORBAN MODEL 8500S
All Five-Band factory presets automatically use
A
LLPASS
because of its
smooth, shelving behavior and low delay. Its allpass characteristic com-
plements the existing phase rotator that reduces voice distortion. Be-
cause the Five-Band structure uses phase-rotating crossovers in the five-
band compressor / limiter, there is little or nothing to be gained by using
a phase-linear crossover in the Five-Band structure’s AGC.
L
I
N
O
D
LY
(Linear-Phase; no delay)
is a phase-linear crossover whose upper band is de-
rived by subtracting its lower band from the crossover’s input. When the upper and
lower bands have the same gain, their sum is perfectly flat with no phase rotation.
However, when the upper and lower bands have different gains, peaks and dips ap-
pear in the frequency response close to the crossover frequency.
L
I
N
O
D
LY
is useful if you need a crossover with low delay and no phase
distortion when flat. Its downside is the possibility of coloration when
the gains of the two bands are widely disparate.
L
INEAR
is a phase-linear crossover whose upper band is derived by subtracting its
lower band from the crossover’s input, as passed through a delay equal to the group
delay of the lowpass crossover filter. The overall frequency response remains smooth
as the two bands take different degrees of gain reduction—the response is a smooth
shelf without extra peaks or dips around the crossover frequency. The two bands are
each down 6 dB at the crossover frequency. This crossover has constant delay even
when the two bands have unequal gains.
While
L
INEAR
has the ideal combination of no phase distortion (even
when non-flat) and smooth shelving behavior, it adds about 4 ms to the
overall delay (compared to
A
LLPASS
and
L
I
N
O
D
LY
), so it is not a good
choice if you need to drive talent headphones.
Peak Limiter Controls
The clipper controls are common to the Two-Band and Five-Band structures, except
as noted in the control descriptions on the following pages.
Bass Clip Mode
sets the operation of the bass clipper to
H
ARD
,
LL
H
ARD
,
M
EDIUM
, or
S
OFT
.
•
H
ARD
operates the clipper like the clipper in the 8200. It produces the most har-
Clipper Controls
Full Modify Name
Advanced Name
Range
--- Overshoot
Compensator
Drive
–2.0 … +2.0
BASS CLIP
Bass Clip Threshold
–6.0 … 0.00
Bass Clip Shape
0 … 10
FINAL CLIP
Final Clip Drive
–3.0 … +5.0
COMP DRV
Composite Limiter Drive
Off, 0 ... 3 dB
Speech Bass Clip
–6.0 … 0.00
MPX LIMIT MODE
MPX Limiter Mode
Hard, HalfCos
Table 3-5: Clipper Controls
Summary of Contents for OPTIMOD-FM 8500S
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