Orban OPTIMOD-FM 8700, Руководство по эксплуатации

Страница: 181 / 390

OPTIMOD-FM DIGITAL OPERATION
3-11
If input program material below 45 Hz is present, the subharmonic synthesizer au-
tomatically reduces the level of the synthesized subharmonics to prevent excess
build-up of energy below 45 Hz.
To prevent introducing unnatural coloration in male speech. the subharmonic syn-
thesizer is defeated when the automatic speech/music detector detects speech.
Multiband Compression: The multiband compressor/limiter can be operated in five-
band or two-band mode. The 8700i controls high frequencies with distortion-
canceled clipping and, in all but 5-band MX presets, with a high frequency limiter as
well. The clipper operates at 256 kHz-sample rate and is fully anti-aliased.
Usually, the gain reduction in band 5 is slaved to the gain reduction in band 4 (as
determined by the setting of the
B4 > B5 C
OUPLE
control); these bands are only in-
dependent from the viewpoint of the downward expander and multiband clippers.
However, a high frequency limiter causes additional gain reduction in band 5 when
band 5 multiband clipping alone would be insufficient to prevent HF distortion. The
HF limiter uses a sophisticated analysis of the signal conditions in the 8700i’s clipping
system to do this.
Except in MX presets, a clipper, embedded in the crossover, protects bands 1 and 2
from transient overshoot. This clipper has a shape control, allowing you to vary the
“knee” of its input/output transfer curve from hard (0) to soft (10). Instead of a clip-
per, MX presets use a sophisticated bass pre-limiter located immediately before the
system’s main distortion-controlled clipper.
In non-MX presets, the multiband compressor/limiter offers look-ahead compression
to minimize overshoot and its associated clipping distortion. This look-ahead func-
tionality can be turned on or off manually, or the 8700i’s speech/music detector can
activate it automatically.
The Ultra-low Latency structure does not offer compressor look-ahead.
“Intelligent” Clipping: In non–MX presets, the 8700i prevents excess clipping distor-
tion by dynamically reducing the drive level to the clippers as required, using an in-
telligent analysis of the clipping distortion produced in the final clipper and over-
shoot compensator.
To minimize latency, the Ultra-low Latency structure does not have this
feature. This is the principal reason why it achieves less on-air loudness
that the optimum-latency and low-latency processing for a given amount
of distortion.
MX presets use an advanced peak limiting structure that uses additional “intelli-
gence,” novel processing structures, and other strategies to produce lower perceived
distortion with “difficult” program material. This peak limiter also offers substantial-
ly improved transient impact and high frequency power handling capability com-
pared to the “intelligent” clipping in the non–MX presets.
Speech Mode: You can set many of the processing parameters separately for speech
signals, as detected by the 8700i’s speech/music detector. This allows you to tune the
processing separately for speech and music.