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The filters

Official support for: zynaddsubfx.sourceforge.net

Moderator: paulnasca

109 posts since 10 Nov, 2013, from Germany

Postby Chris-S; Fri Dec 20, 2013 1:22 am

what is the difference between LPF1 and LPF2 and what is the setting
to get a classic 24 dB/oct low pass filter?

LPF2 2x ?

199 posts since 21 Oct, 2008, from USA

Postby fundamental; Fri Dec 20, 2013 12:32 pm

The difference is the resonance.
Just take a look at the filter diagrams at http://zynaddsubfx.sourceforge.net/Doc/

As per the 24dB/octave, the 4 pole filter (LP2 with 2 stages) sounds about right.
Either that or 4x LP1 should work.
ZynAddSubFX developer
109 posts since 10 Nov, 2013, from Germany

Postby Chris-S; Sat Dec 21, 2013 2:50 am

thanks, I just confirmed this by doing some measurements with audacity.


And I guess the StateVariable Filter is just another algorithm for the

Concerning wikipedia this kind of filter is often used in synths.


Edit: 24 dB/Oct is LP2 x 4 concerning to my measurement, not LP2 x 2
Last edited by Chris-S on Sun Dec 22, 2013 1:25 pm, edited 1 time in total.
User avatar
382 posts since 3 Jul, 2006

Postby jackoo; Sun Dec 22, 2013 4:18 am

Hi Chris-S,

That is weird. I would have expected the same as fundamental. LP2 has two poles (that can also resonate) so LPx2 should be 4 poles. One pole means 6dB / octave (if I properly recall).

How did you carry on your measurement? Pure sine wave?
109 posts since 10 Nov, 2013, from Germany

Postby Chris-S; Sun Dec 22, 2013 10:59 am

Yes, sine wave played on different octaves.
And filter tracking of course equal to zero.

Moderator: paulnasca

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