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3-2
Operation
Simple wideband look-ahead limiting can still produce audible intermodulation distortion between heavy bass and
midrange material. The lookahead limiter in your OPTIMOD uses sophisticated techniques to reduce such IM
distortion without compromising loudness capability.
Distortion in Processing
In a competently designed processor, distortion occurs only when the processor is controlling peaks to prevent the
audio from exceeding the peak modulation limits of the transmission channel. The less peak control that occurs, the
less likely that the listener will hear distortion. However, to reduce the amount of peak control, you must decrease
the drive level to the peak limiter, which causes the average level (and thus, the loudness) to decrease proportionally.
Loudness and Distortion
In FM processing, there is a direct trade-off between loudness, brightness, and distortion. You can improve one only
at the expense of one or both of the others. Thanks to Orban's psychoacoustically optimized designs, this is less true
of Orban processors than of others.
In the 5750, the tradeoff between brightness and the other two parameters has been considerably improved (by 2.5
– 3 dB above 6 kHz) when an "MX" preset is active compared to when an "8500-style" preset is active. Nevertheless,
all intelligent processor designers must acknowledge and work within the laws of physics as they apply to this trade-
off.
Perhaps the most difficult part of adjusting a processor is determining the best trade-off for a given situation. We
feel that it is usually wiser to give up ultimate loudness to achieve low distortion. A listener can compensate for
loudness by simply adjusting the volume control. However, there is nothing the listener can do to make an
excessively compressed or peak-limited signal sound clean again.
If processing for high quality is done carefully, the sound will also be excellent on small radios. Although such a signal
might fall slightly short of ultimate loudness, it will tend to compensate with an openness, depth, and punch (even
on small radios) that cannot be obtained when the signal is excessively squashed.
OPTIMOD 5750—from Bach to Rock
You can adjust the OPTIMOD-5750 so that the output sounds:
•
As close as possible to the input at all times (using the Two-Band structure), or
•
open but more uniform in frequency balance (and often more dramatic) than the input (using the Five-Band
structure with slow release times), or
•
dense, quite squashed, and very loud (using the Five-Band structure with fast or medium-fast release times).
The dense, loud setup will make the audio seem to jump out of car and table radios, but may be fatiguing and invite
tune-outs on higher quality home receivers. The loudness/distortion trade-off explained above applies to any of
these setups.
You will achieve best results if Engineering, Programming, and Management go out of their way to communicate
and cooperate with each other. It is important that Engineering understand the sound that Programming desires,
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