Wheatstone Corporation D-7, Technical Manual, Page: 77 / 92

D y n a m i c s P r o c e s s i n g C o n t r o l G U I
page 8 – 8
D-7 / Nov 2006
Compressor Settings
The compressor algorithm used in the D-7 is designed to:
- prevent really ghastly noises
from being achieved too easily;
- allow smooth, inaudible, and
unobtrusive level control on uneven
sources;
- be able to act as a peak limiter
for inadvertent overload control;
- enable deep effects if required.
The D-7 compressor section is a
compound of many diverse
dynamics elements.
The level detector is a pseudo-
RMS averaging type with its own
symmetrical-in-time attack-and-re-
lease characteristic adjustable be-
tween 0.1mS and 330mS (“Attack”
control). At the slower end of its
range, by itself it achieves a nouveau-classic “dbx” style syllabic-rate level
control. As the time-constant is shortened, it becomes progressively shorter
in relation to the lower audio frequencies themselves; the effect is to turn the
detector into more of a peak-level detector, necessary for limiting or wilder
effects. A secondary effect at intermediate to fast attack-times is that low
frequencies are peak sensed while high frequencies are average sensed
resulting in an effective high-frequency bias (up to as much as 6dB differen-
tial) which helps to mitigate the detrimental limiting effect of the resulting
audio seeming “bottom heavy” normal to most compressors.
While the overall gain-reduction scheme is “feed-forward”, the heart of
the detector stage itself is a feedback limiter; this allows for this carefully-
contrived loosely-damped servo-loop to permit far more interesting dynamic
effects than the analytically perfect but deathly boring deterministic classic
feed-forward detection schemes typically afford.
The compressor is “soft-knee”, meaning the compression ratio
increases slowly with increasing applied level, greatly easing the sonic
transition into full compression; it helps avoid the “snatching” and “pump-
ing” at threshold that many “hard-knee” dynamics units exhibit.
A full range of controls is available over the compressor’s behavior:
CMP — A switch that allows the compressor to be enabled and disabled.
POST EQ — Determines whether the compressor is effectively inserted
after the equalizer or before the equalizer. In general, pre-EQ is a better
option on pre-processed program material while post-EQ allows the ex-
cesses of a “raw” source signal to be tamed prior to exciting the dynamics.
THRESHOLD (-30.0dB - +10.0dB) — Threshold, the level above which
gain reduction is applied.