E-Mu Planet Phatt Operation Manual page 53

PROGRAMMING BASICS
Another control on the filter is called Q or resonance. On a lowpass or
highpass filter, turning up the Q of the filter emphasizes the frequen-
cies around the cutoff frequency. The chart below shows how different
amounts of Q affect the lowpass filter response. In terms of sound,
frequencies around the cutoff will tend to "ring" with high Q settings.
If the filter is swept back and forth slowly with a high Q, various
overtones will be "picked out" of the sound and amplified as the
resonant peak sweeps over them. Bells and gongs are real world ex-
amples of sounds which have a high Q.
Low Q Med Q High Q
Frequency
Turning up the "Q" will emphasize the frequencies around the cutoff point.
Another important feature of a filter is the number of poles it con-
tains. The lowpass filters on Planet Phatt can be either 2-pole, 4-pole
or 6-pole filters. The highpass and bandpass filters can be either 2nd or
4th order filters another way to describe the number of filter sections
they contain. The number of poles in a filter describes the steepness of
its slope and the more poles the steeper the slope, which in turn
affects the sound. In general, the 2-pole filter will have a buzzier
sound and the 4-pole filter has the classic low pass resonant filter
sound. Planet Phatt's 6-pole low pass filters create a tight, modern
sound.
6-pole 4-pole 2-pole
Frequency
Chapter 4: Programming Basics 45