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B2-SWM-Op-Guide-v4.pmd 030108-hto
SECTION EIGHT : COMPRESSOR SET UP
8.1 Basics of Compression
The dynamic range (how loud we can hear to how quiet a sound we can detect) of the human ear is far
greater than the capacity of sound systems to reproduce. Although some of this equipment limitation is
at the upper extreme of the dynamic range (where too loud a signal will produce distortion), much of the
restriction occurs at the low level end, where the signal disappears below the “noise floor” of the circuitry.
A compressor (or in its most powerful form, a limiter) is the most widely used tool for controlling dynamic
range. In the simplest terms, a compressor is designed to squeeze the dynamic range of an audio
program; i.e., to make quiet signals louder, and loud signals quieter. A compressor becomes a limiter
when the compression ratio (the ratio of the input gain change to the output gain change) is so high that
the output level won’t rise above a “brick wall” ceiling regardless of how loud the input gets (typically 10:1
and greater).
A compressor acts like an “automatic mix engineer” with a hand on the fader and an inhumanly fast
reaction time. When the input level increases, the engineer drops the fader; when the level decreases,
the fader is raised. When the amount of fader compensation equals the variation in signal level, the
output level of the audio program will sound consistent.
The practical benefits of compression and limiting include:
1. Speaker protection. A compressor will control sudden level peaks and prevent your speakers from
damage.
2. Perceived increase in loudness. Because peak levels are kept from rising as high as uncompressed
signals, you gain headroom for your audio program and can raise its overall average gain. Compres-
sion is often added to the entire audio mix, both in live sound and recording, to increase its perceived
loudness.
3. Consistent Level. For expressive instruments or vocals, which may have a large dynamic range,
compression can help maintain consistent mix levels. So a speaker who varies from a whisper to a
shout will not disappear or stand out in the mix, relative to other less dynamic instruments.
8.2 Using the Compressor
Compressor controls are located immediately
to the right of the FBX and De-esser panels. The
controls consist of standard Ratio, Thresh
(threshold), and Attack knobs, and a horizontal
LED ladder showing compressor gain reduction.
Ratio:
Compression ratio is the ratio of
the input gain change to the out-
put gain change. The compression ratio on your Sabine Wireless ranges from 1:1 to infin-
ity:1 (limiting).
Thresh:
Compression threshold is the level at which the compressor/limiter begins to act on the
signal. The input level threshold at which compression is engaged can be adjusted from
-30 dBV to 0 dBV.
Attack:
Compressor attack time is the time it takes to compress after a strong signal reaches the
threshold level.
NOTE 1 : Use the mixer channel or amp gain for gain make-up after compression.
NOTE 2 : Default Release Time for the True Mobility Compressor is 400 mSec with the Knee set to
Soft.
Section Eight : Compressor Set Up
Figure 8a - Compressor Section
Ratio
Control
Knob
Threshold
Control
Knob
Attack
Control
Knob
Summary of Contents for TRUE MOBILITY WIRELESS SYSTEM SWM3000
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