Hi, I'm developing an iOS app using libpd.

I tried using coefficient biquad filter and fexpr~ filter to build resonance controllable low, high, bandpass filter.

But if I use only 2 of them in one patch, the CPU usage reaches over 90% already.

I want to know if there's more efficient way to build resonance controllable filters.

I know [vcf~] can do simple bandpass filter but what if I want to make a lowpass filter with a resonance control?

Any suggestion??

fexpr-filters need an insane amount of cpu. cpole~/czero~ based ones are much
more efficient. examples of how to get the pole/zero positions
from coefficients can be found in the rj-lib, mmb-master (biquad)
and in my own instruments.

the other output of vcf~ is also a lowpass.

Thank you mnb. You are so genius!