onepole~ newbie doubt (what is 0.052456 ?)


    Nov 02 2016 | 1:11 am
    Hi everyone, I'm a newbie and I'm studying [onepole~] object. In the help patch - in the highpass example - there's a curiously precise detail: the cutoff frequency is obtained with a slider that is the exponent of the base 2. Actually the exponent is the slider multiplied by a very precise number: 0.052456. It can't be a random number. So, my question is: why precisely that number? What does it mean?
    My second question is about the basic example: the two [filtergraph~] objects describe amplitude response and phase response. What does it mean? That applying a lowpass filter it changes also the phase around the cutoff frequency? And if so, why?
    Thanks a lot for your help!

    • Nov 02 2016 | 10:43 am
      I don't see anything special about 0.052456 in the context of onepole~. It determines the frequency range of the filtersweep in the help patch. It does map values into a reasonable range, but any similar value would be equally effective in this example.
      Yes, applying a lowpass filter affects the phase of the output. Short answer: digital filters that act in the time domain are networks of delays; some of the previous input or output samples are combined with the current sample to get the output value. The delay period naturally has an affect on the phase of components, depending on their frequency. Check out allpass~ for an interesting example.
      Here's the super-long answer: https://ccrma.stanford.edu/~jos/filters/
    • Nov 02 2016 | 1:54 pm
      And here's my super-thank-you mzed :)