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3.1 What Is A Compellor?
A Compellor is the first and only product designed specifically for the transparent control of
audio levels. While other audio processors are designed simply to compress and limit audio
signals, a Compellor is designed to intelligently manage the dynamic range of audio without
causing noticeable changes to the character and feeling of the sound. Contained within the
Compellor are three gain controllers: a frequency discriminate leveler, a compressor, and a
limiter, all working interactively. In addition, a dynamic verification gate, silence gate, and
dynamic release computer intelligently guide the operation of the gain controllers to assure
the least noticeable processing effects will be generated.
The name “Compellor” is a combination of “Compressor-Leveler-Limiter”.
3.2 What Does It Do?
Simply stated, a Compellor automatically evens out the varying levels in an audio system
without making itself noticed. It may seem odd to have a processor you wouldn’t notice work-
ing, but imagine being able to keep a wandering vocal track just right in the mix as if the talent
were using perfect voice techniques. Imagine a TV show that always sounded just the right
level even though scene changes were wide ranging. Now imagine these things without any
background swells, pinched voices, or holes punched by a transient hitting the limiter. If you
can, then you realize just a few things the Compellor can accomplish.
Without a Compellor, it is usual to insert a compressor or limiter in the line to control varying
levels. That always results in degraded sound due to the processing by-products. Lost punch,
overly fat backgrounds, inversion (when a loud sound gets lower than average), suck-down
by transients, and noise swell ups are typical problems encountered with usual processing.
The Compellor was designed specifically to avoid all of these problems and more.
3.3 How Does It Work?
Standard compressors and limiters process the sound on arbitrary principles of level detec-
tion, something like an audio VU or peak meter. Our hearing is a much more complex pro-
cess and we can readily hear the “attenuate and recover” effects caused by these simpler
devices.
In contrast, a Compellor automatically detects and corrects the sound level according to how
we hear, and therefore seems natural and relatively undetectable. The unique and patented
circuitry in a Compellor resulted from years of experiments in audio processing and creates
the only level controller on the market designed specifically to be as “transparent” to the ear
as possible. Additional information about the processing circuits in a Compellor will be found
in the various sections of this manual.
3.4 A Bit Of Compellor History
At first, there was a controversy about whether a Compellor actually did anything. Engineers
would call up and complain they couldn’t hear the difference between “in” and “out” of the