Orban OPTIMOD-FM 8700, Operating Manual

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OPERATION ORBAN MODEL 8700i
These are the only two-band presets. To achieve the equivalent of an
8500
PROTECTION preset, use the CLASSICAL-2B preset. To achieve
higher performance in protection applications, use the CLASSIC-2B MX
preset instead.
Classical music is traditionally broadcast with a wide dynamic range. However, with
many recordings and live performances, the dynamic range is so great that the quiet
passages disappear into the noise on most car, portable, and table radios. Conse-
quently, the listener either hears nothing, or must turn up the volume control to
hear all the music. Then, when the music gets loud, the radio blasts and distorts,
which makes listening unpleasant.
The Two-Band structure is well suited for classical formats during daytime hours
when most people in the audience are likely to be listening in autos or to be using
the station for background music. This audience is best served when the dynamic
range of the program material is reduced by 10-15 dB so that quiet passages in the
music never fade into inaudibility under these less-favorable listening conditions.
OPTIMOD-FM controls the level of the music in ways that are, for all practical pur-
poses, inaudible to the listener. Low-level passages are increased in level by up to 10
dB, while the dynamics of crescendos are maintained.
The CLASSICAL-2 BAND and CLASSIC-2B MX presets are two-band presets with the
AGC turned off. They use considerable bass coupling to preserve the spectral bal-
ance of the input as well as possible. Their
L
ESS
-M
ORE
controls primarily affect the
amount of compression, not the maximum loudness.
CLASSICAL-2B+AGC
AND
CLASSIC-2B+AGC MX use the AGC set for 2:1 compression
ratio. Because of the AGC, these presets affect more of the total dynamic range of
the recording that does the
CLASSICAL-2 BAND preset. However, the AGC provides
extremely smooth and unobtrusive compression because of the gentle ratio and
window gating. In this preset, the Two-Band compressor is used very lightly with a
fast release time as a peak limiter. The AGC does almost all of the compression.
During the evening hours when the audience is more likely to listen critically, a clas-
sical station may wish to switch to a custom preset (derived from the
CLASSIC-2B
MX or CLASSICAL-2 BAND presets) that performs less gain reduction. You can create
such a preset by modifying the CLASSICAL-2 BAND preset with the L
ESS
-M
ORE
con-
trol—turn it down to taste.
There are also four five-band classical presets—two presets and their MX
variants. The MX variants of the
CLASSICAL
presets achieve the lowest
distortion and most open high frequencies. The CLASSICAL-5 BAND pre-
set uses the five-band structure with AGC defeated. It uses substantial in-
terband coupling to retain much of the frequency balance of the original
source, but is capable of somewhat more “automatic equalization” than
is
CLASSICAL-2 BAND . It can therefore re-equalize older program mate-
rial, but there is also more risk that it will cause coloration that might of-
fend the classical purist.
CLASSICAL-5B+AGC, like its two-band counterpart, uses the AGC set for
2:1 compression ratio.