ABSYNTH 5 Reference Manual – 67
5.5.4 Lowpass
Lowpass Filter LPF 2 Pole
The lowpass lters weaken the signal above an adjustable cutoff frequency. The slope gradient
of the signal attenuation is given in dB per octave. A value of -12dB/octave means that the
lter dampens the signal by 12dB more at one octave higher. Other values for slope gradi-
ent are -6dB and -24dB.
The slope gradient can also be referred to as the n-pole (this is the most usual case with
synthesizers and other electronic sound generators). Most of the time, n stands for an even
number between 2 and 8. This data can be easily translated into the dB/octave schema if you
remember that every lter pole corresponds to a steepness of -6dB/octave. So a 1-pole lter
has a gadient of -6 dB/octave, a 2-pole lter dampens the signal by -12 dB/octave, and so on.
As a consequence, ABSYNTH 5’s lowpass lter LPF 2 Pole and LPF -12dB have for example
the same slope gradient. The same applies to the LPF 4Pole and LPF -24dB. Yet they sound
different because of their different internal constructions: The rst three lters in the list
below have a softer, rounder character, whereas the lters in the second group sound rougher
and more aggressive.
The following lowpass lters are available in the Type menu:
• LPF2Pole: 2-pole lowpass lter with resonance control and analog design.
• LPF4Pole: 4-pole lowpass lter with resonance control and analog design.
• LPF8Pole: 8-pole lowpass lter with resonance control and analog design.
• LPF-6dB: 1-pole lowpass lter with resonance control.
• LPF-12dB: 2-pole lowpass lter with resonance control.
• LPF-24dB: 4-pole lowpass lter with resonance control.
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