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Compellor
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numerous other devices which effectively control the level differences, but none have the
transparency of the Compellor. These other devices, particularly multiband compressors and
limiters, have a ‘sweet spot’ which renders the best results. Adjust the Compellor so that its
output is driving the downstream processors at their sweet spot.
6.9 Broadcast STL/ Phone Line Driver
The aural STL’s and phone lines have limited dynamic range. It is advisable to do processing
in front of those links so that they are not overloaded or driven so lightly that there is too much
noise. Set the Compellor for 12dB of gain reduction, Process Balance at 11 o’clock, Leveling
Speed ‘slow’, Limiting ‘in’, Stereo Enhance ‘in’ and Leveling Link ‘in’.
6.10 Television Broadcasting and Cable Systems
The single biggest complaint generator from viewers is the apparent level difference between
commercials and program. The differences may be even more exaggerated when there are
local inserts into national feeds. Commercials are processed to have low peak to average
ratios. So even if the peaks of the commercials are the same as the program peaks (as would
be measured on a modulation monitor) the average levels are higher, causing the apparent
loudness difference.
The Compellor recognizes the differences in density and adjusts it release times based on
the peak to average ratio of the input. If an input is already heavily processed (e.g.- a com-
mercial), the Compellor slows its release time. When the Compellor sees a very high peak
to average ratio (e.g.- a live news broadcast) it speeds its release time. Segues between
program and commercials are much smoother.
Another complaint made to cable systems is the difference of levels channel to channel. If
each channel of a cable system has a Compellor and all the Compellors in a cable system
are set similarly, channel to channel differences will be eliminated.
6.11 Video and Audio Tape Duplication
The dynamic range of most tape formats is usually much less than the original source mate-
rial. In addition, the usable dynamic range of the playback medium of duplicated tape is usu-
ally less than that of the original (e.g.- video tape copy of a theatrical release). The Compellor
will automatically control the dynamics of the original without losing the impact and artistic
intent of the original.
The Compellor is also useful when assembling a single tape from multiple sources. The level
differences between the sources are automatically smoothed out, obviating the need for stu-
dio time to level adjust each source before mastering.
6.12 Voice Processing
The human voice is the most difficult signal to process. We may not know what that drum
sounded like originally, but we all know what a human voice sounds like. Processing artifacts
are therefor much more noticeable on human voices.
Consonant recognition is a critical part of intelligibility. If the processing is not done correctly,
the consonants will be ‘crushed’ causing the loss of intelligibility. The Compellor effectively
controls the levels without loss of intelligibility, indeed because the levels are more controlled,
the intelligibility will be enhanced.
It is recommended that Leveling Speed be set for ‘fast’ when processing voices.
6. Operation