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14
Dynamics Processing 101
- Continued
Soft-Knee / Hard-Knee
In order to prevent harsh, unnatural envelopes on compressed signals, sophisticated dynamics processors like the C Com
16 feature an SKD (Smart Knee Detector) or automatic knee circuit. The Smart Knee Detector automatically switches
from Soft-Knee when the signal is less than 10 dB over threshold, to Hard-Knee when the signal is 10db above threshold.
In Soft-Knee mode, there is a gradual affect on gain change, which begins as the signal approaches the threshold level.
In Hard-Knee mode, gain reduction is linear based on the threshold and Ratio controls. Any signal that falls below the
threshold level will be unprocessed.
Noise Gates
Noise gates are used to remove unwanted noise and/or bleed from recorded tracks in the studio or from open micro-
phones in live sound systems. Noise gates can also be used as a sound effect, most commonly to chop the end of a
reverb, let’s say on a snare drum, so that the entire snare sound ends just before the beat. The basic principle of a noise
gate is to work as an automatic mute switch. Mute off (Gate Open) when the desired signal is present and mute on (Gate
Closed) when the desired signal is not present. In order to get the gate to work predictably, it is necessary to set a thresh-
old, or trigger level that will determine when the gate will open. If the signal is below the trigger, the gate will remain
closed. When the signal is above the trigger, the gate will trigger open allowing the desired signal to pass and be heard.
Noise gates often have other adjustable controls like attack, hold, range and release. Many noise gates like those in the
SAMSON S com, S com plus, S com 4 and S gate 4 use sophisticated circuits to control some of these parameters auto-
matically.
Downward Expander
The purpose of a well-designed Downward Expander is to increase the perceived dynamic range of a system. This is
accomplished by decreasing the gain during the softer sections, thereby lowering the relative noise floor. When the sig-
nal level is below the desired trigger level, the expander lowers the overall gain by the selected amount.
Side Chain / External Key
The C Com 16 features a side-chain or external Key function. The external Key function is used to externally process the
compressor’s detector circuit. There are many useful applications for processing the detector circuit including Equalizing
for frequency dependent compression, De-Essing - the use of EQ to remove sibilance, and externally keying off a vocal
track for Ducking effects, to name a few. The Key insert jack sends the compressors trigger signal for external processing,
and then receives the processed signal, which will now control the compressor’s detector.