The Two-Band Structure - Orban OPTIMOD-FM 8500S Operating Manual

3-44
OPERATION

The Two-Band Structure

control away from 0 will change the loss. (For example, setting the
T
HRESHOLD
M P T
ULTIPLEX OWER HRESHOLD
The M
ULTIPLEX
gain.
Regardless of the setting of the M
M P
ULTIPLEX
larger than 0 dB.
The M P O
ULTIPLEX OWER
tions that the multiplex power controller might produce. These can occur because
the ITU specification does not call for psychoacoustic weighting. The Optimod does
not force the multiplex power controller to dynamically produce all of the required
gain reduction (which could vary widely, depending on the program material). In-
stead, the M
P
ULTIPLEX
gain reduction produced by the control is, of course, unchanging and cannot intro-
duce audible artifacts.
The ideal dynamic gain reduction for the multiplex power controller is 2 to 3 dB
with typical program material. However, the actual gain reduction will vary widely
depending on whether the underlying processing preset is "loud" or "quiet." There-
fore, the appropriate setting of the M
strongly on what preset is in use. Accordingly, each preset has its own setting of the
M P O
ULTIPLEX OWER FFSET
preset. Hence, adjustments that affect the multiplex power controller appear in two
independent places in the Optimod: The M
tem setup control, while the M
Depending on the preset, the M
from 0 dB (no effect) to as much as –16 dB. If you customize a preset in any way (in-
cluding using L -M
ESS ORE
that preset so that the multiplex power controller produces 2-3 dB of indicated gain
reduction with typical program material. This will achieve the maximum on-air loud-
ness that complies with the ITU standard while minimizing the potential for unnatu-
ral and audibly disturbing loudness inconsistencies caused by the operation of the
multiplex power controller.
For more information on the multiplex power controller, refer to ITU-R Multiplex
Power Controller on page 3-72.
The Two-Band structure consists of a slow two-band gated AGC (Automatic Gain
Control) for gain riding, followed by an equalization section, a gated two-band
compressor, a high-frequency limiter, and a complex peak limiting system similar to
the one used in the Five-Band structure. Like the "Two-Band Purist" structure in
Orban's OPTIMOD-FM 8200, the 8500S's Two-Band Structure is phase-linear through-
out to maximize sonic transparency.
The Two-Band structure has an open, easy-to-listen-to sound that is similar to the
source material if the source material is of good quality. However, if the spectral bal-
control to +3 will cause the loss to decrease by 3 dB.)
control can only introduce loss, never
P T
OWER HRESHOLD
controls, the resulting gain offset can never be
O
OWER FFSET
control's purpose is to reduce unnatural loudness varia-
FFSET
control produces most of the gain reduction. The
O
OWER FFSET
ULTIPLEX
, which is a processing parameter like any other in a given
ULTIPLEX
P
ULTIPLEX OWER
P
ULTIPLEX
), you may wish to trim the M
ORBAN MODEL 8500S
P T
ULTIPLEX OWER HRESHOLD
P O
OWER FFSET
P T
OWER HRESHOLD
is part of the on-air preset.
O
FFSET
control's setting can vary
O
OWER FFSET
ULTIPLEX
and
control depends
control is a sys-
P O for
OWER FFSET