Kurzweil K2661, Musician’S Reference Manual

Page: 106 / 500

10-24
KDFX Reference
KDFX Algorithm Specifications
15 Finite Verb
Reverse reverberation algorithm.
PAUs: 3
The left and right sources are summed before being fed into a tapped delay line which directly simulates
the impulse response of a reverberator. The taps are placed in sequence from zero delay to a maximum
delay value, at quasi-regular spacings. By varying the coef
fi cients with which these taps are summed, one
can create the effect of a normal rapidly building/slowly decaying reverb or a reverse reverb which builds
slowly then stops abruptly.
A special tap is picked off the tapped delay line and its length is controlled by Dly Length. It can be
summed into the output wet mix (Dly Lvl) to serve as the simulated dry source that occurs after the
reverse reverb sequence has built up and ended. It can also be fed back for special effects. Fdbk Lvl and HF
Damping tailor the gain and spectrum of the feedback signal. Despite the complex reverb-like sound of the
tapped delay line, the Feedback tap is a pure delay. Feeding it back is like reapplying the source, as in a
simple tape echo.
Dly Length and Rvb Length range from 300 to 3000 milliseconds. With the R1 Rvb Env variants, Rvb
Length corresponds to a decay time (RT60).
To make things a little more interesting, the tapped delay line mixer is actually broken into three mixers,
an early, middle, and late mixer. Each mixes its share of taps and then applies the submix to a low pass
fi lter (cut only) and a simple bass control (boost and cut). Finally, the three equalized sub mixes are mixed
into one signal. The Bass and Damp controls allow special effects such as a reverb that begins dull and
increases in two steps to a brighter sound.
The Rvb Env control selects 27 cases of envelope gains for the taps. Nine cases emulate a normal forward
evolving reverb, but with some special twists. Cases FWD R1xx have a single reverb peak, with a fast
attack and slower decay. The sub cases FWD R1Sx vary the sharpness of the envelope, from dullest (S1) to
sharpest (S3). The sub cases FWD R2xx have two peaks; that is, the reverb builds, decays, builds again, and
decays again. The sub cases FWD R3xx have three peaks.
The sub cases SYM have a symmetrical build and decay time. The cases R1 build to a single peak, while R2
and R3 have two and three peaks, respectively.
The sub cases REV simulate a reverse reverb effect. REV R1xx imitates a backward running reverb, with a
long rising "tail" ending abruptly (followed, optionally, by the "dry" source mixed by Dly Lvl). Once again,
the number of peaks and the sharpness are variable.
The usual Wet/Dry and Output Gain controls are provided.
Parameters
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Wet/Dry 0 to 100%wet Out Gain Off, -79.0 to 24.0 dB
Fdbk Lvl 0 to 100%
HF Damping 16 to 25088 Hz
Dly Lvl 0 to 100% Rvb Env REV R1S1
Dly Length 300 to 3000 ms Rvb Length 300 to 3000 ms