Hi Peter -

I believe the graphs are showing phase delay, which people often graph because it's positive. But you're right that the phase response, if measured as (phase out) - (phase in), is negative. I think this is probably best fixed by fixing the example to say that it's showing phase delay, not phase response, or equivalently, saying it's -arg(H) instead of arg(H)... this is probably also wrong in the book. I'd better go look when I have a moment...

thanks Miller On Thu, Feb 13, 2014 at 11:35:20PM +0100, Peter P. wrote:

Hi list,

just wondering if I am getting something wrong plotting the phase response of lop~ using the abstractions filter-graph1.pd and filter-graph2.pd as exemplified in 3.audio.examples/H10.measurement.pd

For a simple one-zero lowpass filter using [rzero~ -1] the phase response is plotted going from 0 to pi/2 (eg. 90°) at nyquist frequency. I always thought that it would be 0^ to -90° though.

Also a highpass [rzero~ 1] filter's phase is plotted as going from -90° to 0° instead of the 90° to 0° I know from some textbooks.

Is there a mistake I could have had made? I mean, things sound alright, but I am just wondering.

best, P

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