Hard- And Soft-Knee Compression Characteristics - Kurzweil K2600 Musician’s Reference

KDFX Reference
KDFX Algorithm Specifications
In the hard-knee compressor, there is a sudden transition from uncompressed to compressed at the
compression threshold. In the soft-knee compressor there is a more gradual transition from compressed to
unity gain.
Figure 10-76
To determine how much to compress the signal, the compressor must measure the signal level. Since
musical signal levels will change over time, the compression amounts must change as well. You can
control the rate at which compression changes in response to changing signal levels with the attack and
release time controls. With the attack time, you set how fast the compressor responds to increased levels.
At long attack times, the signal may over-shoot the threshold level for some time before it becomes fully
compressed, while at short attack times, the compressor will rapidly clamp down on the level. The release
time controls how long it takes the compressor to respond to a reduction in signal levels. At long release
times, the signal may stay compressed well after the signal falls below threshold. At short release times,
the compressor will open up almost as soon as the signal drops.
For typical compressor behaviour, the attack time is considerably shorter than the release time. At very
short attack and release times, the compressor is almost able to keep up with the instantaneous signal
levels and the algorithm will behave more like distortion than compression. In addition to the attack and
release times, there is another time parameter: ÒSmoothTimeÓ. The smoothing parameter will increase
both the attack and release times, although the effect is signiÞcant only when its time is longer than the
attack or release time. Generally the smoothing time should be kept at or shorter than the attack time.
You have the choice of using the compressors conÞgured as feed-forward or feedback compressors. For
feed-forward, set the FdbkComprs parameter to ÒOutÓ; for feedback compression, set it to ÒInÓ. The feed-
forward conÞguration uses the input signal as the side-chain source. The feedback compressor on the
other hand uses the compressor output as the side-chain source. Feedback compression tends to be more
subtle, but you cannot get an instant attack.
In the feedback conÞguration, the signal being compressed may be delayed relative to the side chain
compression processing. The delay allows the signal to start being compressed just before an attack
transient arrives. Since the side chain processing ÒknowsÓ what the input signal is going to be before the
main signal path does, it can tame down an attack transient by compressing the attack before it actually
happens. In the feed-forward conÞguration, the delay affects both the main signal and the side chain, and
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Out
Amp
Out
Amp

Hard- and Soft-Knee Compression Characteristics

Threshold
In Amp
Threshold
In Amp