Operation Manual

SUBTRACTOR SYNTHESIZER
108
➜ Highpass (HP12)
A highpass filter is the opposite of a lowpass filter, cutting out the lower
frequencies and letting the high frequencies pass. The HP filter slope has
a 12 dB/Octave roll-off.
The darker curve illustrates the roll-off curve of the Highpass Filter. The lighter curve
in the middle represents the filter characteristic when the Resonance parameter is
raised.
➜ Notch
A notch filter (or band reject filter) could be described as the opposite of a
bandpass filter. It cuts off frequencies in a narrow midrange band, letting
the frequencies below and above through. On it’s own, a notch filter
doesn’t really alter the timbre in any dramatic way, simply because most
frequencies are let through. However, by combining a notch filter with a
lowpass filter (using Filter 2 - see page 109 in this chapter), more musi-
cally useful filter characteristics can be created. Such a filter combination
can produce soft timbres that still sound “clear”. The effect is especially
noticeable with low resonance (see page 109) settings.
The darker curve illustrates the roll-off curve of the Notch Filter. The lighter curve in
the middle represents the filter characteristic when the Resonance parameter is
raised.