Distortion In Processing; Loudness And Distortion - Orban OPTIMOD 8400 Operating Manual

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OPERATION

Distortion in Processing

Loudness and Distortion

Limiting increases audio density. Increasing density can make loud sounds seem louder,
but can also result in an unattractive busier, flatter, or denser sound. It is important to be
aware of the many negative subjective side effects of excessive density when setting con-
trols that affect the density of the processed sound.
Clipping sharp peaks does not produce any audible side effects when done moderately.
Excessive clipping will be perceived as audible distortion.
Look-ahead limiting is limiting that prevents overshoots by examining a few milliseconds
of the unprocessed sound before it is limited. This way the limiter can anticipate peaks
that are coming up.
The 8400 uses look-ahead techniques in several parts of the processing to
minimize overshoot for a given level of processing artifacts, among other
things.
In a competently designed processor, distortion occurs only when the processor is con-
trolling 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.
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 any
others. 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.
If women form a significant portion of the station's audience, bear in mind that women
are more sensitive to distortion and listening fatigue than men are. In any format requir-
ing long-term listening to achieve market share, great care should be taken not to alienate
women by excessive stridency, harshness, or distortion.
ORBAN Model 8400