Kurzweil K2661, Musician’S Reference Manual

Page: 296 / 500

10-214
KDFX Reference
KDFX Algorithm Specifications
956 Compress 3 Band
Stereo soft-knee 3 frequency band compression algorithm
PAUs: 4
The 3 band compressor divides the input stereo signal into 3 frequency bands and runs each band through
its own stereo soft-knee compressor. After compression, the bands are summed back together to produce
the output. You may set the frequencies at which the bands are split.
The compressors reduce the signal level when the signal exceeds a threshold. The amount of compression
is expressed as a ratio. The compression ratio is the inverse of the slope of the compressor input/output
characteristic. The amount of compression is based on the sum of the magnitudes of the left and right
channels. A compression ratio of 1:1 will have no effect on the signal. An in
fi nite ratio, will compress all
signal levels above the threshold level to the threshold level (zero slope). For ratios in between in fi nite and
1:1, increasing the input will increase the output, but by less than it would if there was no compression.
The threshold is expressed as a decibel level relative to digital full-scale (dBFS) where 0 dBFS is digital full-
scale and all other available values are negative.
Figure 10-112 Band Compressor
In the soft-knee compressor there is a gradual transition from compressed to unity gain.
Figure 10-113 Soft-Knee Compression Characteristics
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
Band
Split
Fil-
ters
Compressor
Compressor
Compressor
L Output
R Output
L Input
R Input
2
2
2
2
2
2
2
Out
Amp
In Amp
Threshold