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 frequencies 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 examples of sounds which have a high Q.
Amplitude
Amplitude
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 contains. 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.
