OPTIMOD-FM OPERATION
3-51
unprocessed sound that sounds just right on music and voice when listened to
on small table radios, car radios, portables, or home hi-fi systems.
The Medium Fast settings (
MFast and MFast2) are ideal for a highly competi-
tive Contemporary Hit Radio (CHR) format whose ratings depend on attract-
ing a large number of listeners (high “cume”) but which does not assume that a
listener will listen to the station for hours at a time. This is the major market
competitive sound, emphasizing loudness as well as clean audio. The sound
from cut to cut and announcer to announcer is remarkably consistent as the
texture of music is noticeably altered to a standard. Bass has an ever-present
punch, there is always a sense of presence, and highs are in perfect balance to
the mids, no matter what was on the original recording.
The Fast setting is used only for the
TALK and SPORTS factory programming
formats. Processing for this sound keeps the levels of announcers and guests
consistent, pulls low-grade telephone calls out of the mud, and keeps a proper
balance between voice and commercials. Voice is the most difficult audio to
process, but these settings result in a favorable trade-off between consistency,
presence, and distortion.
The Factory Presets for this sound are quite different from the other three re-
lease time settings. The amount of gain reduction in the multiband compres-
sor is substantially lower (so that it operates more like a limiter than like a
compressor), and the release time of the gain-riding AGC is speeded up (so
that it provides compression and some increase of density). We made these
trade-offs to prevent excessive build-up of density.
There is nothing written in stone saying that you can’t experiment with this
sound for music-oriented programming as well. However, even with these set-
tings, your sound is getting farther away from the balance and texture of the
input. We think that this is as far as processing can go without causing unac-
ceptable listener fatigue. However, this sound may be quite useful for stations
that are ordinarily heard very softly in the background because it improves in-
telligibility under these quiet listening conditions. Stations that are ordinarily
played louder will probably prefer one of the slower release times, where the
multiband compressor takes more gain reduction and where the AGC is oper-
ated slowly for gentle gain riding only. These slower sounds are less consistent
than those produced by the
Fast setting. Using Slow preserves more of the
source’s frequency balance, making the sound less dense and fatiguing when
the radio is played loudly.
MB Gate Thresh (Threshold)
control determines the lowest input level that will be rec-
ognized as program by OPTIMOD-FM; lower levels are considered to be noise or back-
ground 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 8400. The first affects the AGC and the
second affects the multiband compressor. Each has its own threshold control.
The multiband compressor gate causes the gain reduction in bands 2 and 3 of the multi-
band compressor to quickly move to the average gain reduction occurring in those bands
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