Kurzweil K2661 - Panaural Room; Room Reverberation Algorithm; Simplified Block Diagram of Panaural Room

10-16
KDFX Reference
KDFX Algorithm Specifications
12 Panaural Room
Room reverberation algorithm
PAUs: 3
The Panaural Room reverberation is implemented using a special network arrangement of many delay
lines that guarantees colorless sound. The reverberator is inherently stereo with each input injected into
the "room" at multiple locations. The signals entering the reverberator first pass through a shelving bass
equalizer with a range of +/-15dB. To shorten the decay time of high frequencies relative to mid
frequencies, low pass filters controlled by HF Damping are distributed throughout the network. Room
Size scales all the delay times of the network (but not the Pre Dly or Build Time), to change the simulated
room dimension over a range of 1 to 16m. Decay Time varies the feedback gains to achieve decay times
from 0.5 to 100 seconds. The Room Size and Decay Time controls are interlocked so that a chosen Decay
Time will be maintained while Room Size is varied. A two input stereo mixer, controlled by Wet/Dry and
Out Gain, feeds the output.
Figure 10-4 Simplified block diagram of Panaural Room.
The duration and spacing of the early reflections are influenced by Room Size and Build Time, while the
number and relative loudness of the individual reflections are influenced by Build Env. When Build Env is
near 0 or 100%, fewer reflections are created. The maximum number of important early reflections, 13, is
achieved at a setting of 50%.
To get control over the growth of reverberation, the left and right inputs each are passed through an
"injector" that can extend the source before it drives the reverberator. Only when Build Env is set to 0% is
the reverberator driven in pure stereo by the pure dry signal. For settings of Build Env greater than 0%, the
reverberator is fed multiple times. Build Env controls the injector so that the reverberation begins abruptly
(0%), builds immediately to a sustained level (50%), or builds gradually to a maximum (100%). Build Time
varies the injection length over a range of 0 to 500ms. At a Build Time of 0ms, there is no extension of the
build time. In this case, the Build Env control adjusts the density of the reverberation, with maximum
density at a setting of 50%. In addition to the two build controls, there is an overall Pre Dly control that can
delay the entire reverberation process by up to 500ms.
PreDelay
PreDelay
Reverb
Dry
Dry
Out Gain
L Output
R Output
L Input
R Input
Wet