paulnasca

Chris-S · Post by **Chris-S** » Fri Dec 20, 2013 9:22 am

Dears,
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 ?

Greetings

fundamental · Post by **fundamental** » Fri Dec 20, 2013 8:32 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.

Chris-S · Post by **Chris-S** » Sat Dec 21, 2013 10:50 am

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

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

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

Chris

Edit: 24 dB/Oct is LP2 x 4 concerning to my measurement, not LP2 x 2

jackoo · Post by **jackoo** » Sun Dec 22, 2013 12:18 pm

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?

Chris-S · Post by **Chris-S** » Sun Dec 22, 2013 6:59 pm

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

paulnasca

KVR Audio

The filters