notechnotech

I have a biquad~ object in one of my subpatchers.   It appears to only be working correctly at when sampling rate is set to 44.1 (i'm thinking this might of been my sample rate when i created the object)

When i update sample rates, i am getting significantly different results..  Am i missing something where when I change sampling rates, i need to let biquad~ know ?

biquad-at-different-sampling-rates

how do you calculate the coefficients for the filters?

i calculated them once using filtergraph.

I then put the coefficients into a message box and loadbang it into biquad~

(The filter isn't suppose to change, i just want it to always filter out this specific frequency).

looking at this again, I didn't realize filtergraph was an audio object. (and thus the sample rate probably has an effect on the coefficients)

I'm guessing I just need to have a filtergraph~ from the max example, and have it bang message boxs with the predetermined cuttoff, filtertype,etc anytime the samplerate changes..

or figure out how to compute the coefficients myself. i just want a simple bandstop.

i calculated them once using filtergraph.
I then put the coefficients into a message box and loadbang it into biquad~
(The filter isn't suppose to change, i just want it to always filter out this specific frequency).

I'm guessing I just need to have a filtergraph~ from the max example, and have it bang  message boxs with the predetermined cuttoff, filtertype,etc anytime the samplerate changes..

or figure out how to compute the coefficients myself.  i just want a simple bandstop.


actually filtergraph~ automatically updates when the samplerate changes. easy fix. thanks !

actually filtergraph~ automatically updates when the samplerate changes.  easy fix. thanks !


biquad~ at different sampling rates