Rotating Speaker With Virtual Microphones - Kurzweil K2661 Musician’s Reference Manual

microphone. The signal is then passed through a final lowpass filter to simulate the band-limiting effect of
the speaker cabinet.
Figure 10-44

Rotating speaker with virtual microphones

For the rotating speakers, you can control the cross-over frequency of the high and low frequency bands
(the frequency where the high and low frequencies get separated). The rotating speakers for the high and
low frequencies have their own controls. For both, the rotation rate, the effective driver size and tremolo
can be set. The rotation rate of course sets how fast the rotating speaker is spinning. The effective driver
size is the radius of the path followed by the speaker relative to its center of rotation. This parameter is
used to calculate the resulting Doppler shift of the moving speaker. Doppler shift is the pitch shift that
occurs when a sound source moves toward or away from you the listener. In a rotating speaker, the
Doppler shift will sound like vibrato. As well as Doppler shift, there will be some acoustic shadowing as
the speaker is alternately pointed away from you and toward you. The shadowing is simulated with a
tremolo over which you can control the tremolo depth and "width". The high frequency driver (rotating
horn) will have a narrower acoustic beam width (dispersion) than the low frequency driver, and the
widths of both may be adjusted. Note that it can take up to one full speaker rotation before you hear
changes to tremolo when parameter values are changed. Negative microphone angles take a longer time to
respond to tremolo changes than positive microphone angles.
Figure 10-45 Acoustic beams for (i) low frequency driver and (ii) high frequency driver
You can control resonant modes within the rotating speaker cabinet with the Lo and Hi Resonate
parameters. For a realistic rotating speaker, the resonance level and delay excursion should be set quite
low. High levels will give wild pitch shifting.
(i) (ii)
KDFX Reference
KDFX Algorithm Specifications
10-107