Info on "Theta-Processing" for flangers

[DrAlx]

So after correcting the formula in the last post, I tried using lots of feedback in the phaser arm and very little in the flanger ...

http://www.wolframalpha.com/input/?i=plot+abs%28P%2F%281-0.9*P%29%2BD%2F%281-%C2%AD0.01*D%29%29+where+D%3Dexp%28-%C2%AD2*pi*ix%29+and+P%3D%28%28pi*ix%C2%AD-6%29%2F%28pi*ix%2B6%29%29%5E6+from+x%3D0+to+10


then you only see the flanger peaks/notches way above all the phaser notches.  Interesting. 

[armdnrdy]

Okay...good!

So I might be on to something?

How do we turn this into one of the graphs that I understand like this?



Like I said...I like the pretty pictures! 

[DrAlx]

For 1% delay feedback (i.e. 0.01) and 90% phaser feedback (i.e. 0.9) you get plot like this...

http://www.wolframalpha.com/input/?i=plot+abs%28P%2F%281-0.9*P%29%2BD%2F%281-%C2%AD0.01*D%29%29+where+D%3Dexp%28-%C2%AD2*pi*ix%29+and+P%3D%28%28pi*ix%C2%AD-n%29%2F%28pi*ix%2Bn%29%29%5En+from+x%3D0+to+10+and+n+%3D+0+to+8


So when n  = 0 (i.e. no all pass stages) you get regular flanger notches.
As number of stages (n) increases you get something that is strongly dominated by the phaser response.
Problem with the contour plot is it can hide a lot of the detail. So if you know how many all-pass stages you want to use, you are best  using the regular line plot (that basically takes a horizontal slice through the contour plot).

[armdnrdy]

So...after viewing this last "experiment"...I wonder if the "right" mix of flanger and all-pass stage feedback would enter the realm of something sonically interesting.

It seems that the lower frequencies take on the appearance of a phaser...but as you stated, with the peaks of a flanger.

[DrAlx]

The phaser peaks don't move about with the flanger delay.
Compare the following 3 three pictures.  With each successive picture, the BBD delay is halved.
Notice that the locations of those big phaser peaks don't change, only the flanger peaks do (they're close together in the first picture and far apart in the last).

So you are effectively just getting a fixed filtering of what would otherwise be a regular pattern of peaks and troughs.  So my guess is it would just sound like a flanger with some EQ applied to it.

http://www.wolframalpha.com/input/?i=plot+abs%28P%2F%281-0.9*P%29%2BD%2F%281-%C2%AD0.01*D%29%29+where+D%3Dexp%28-%C2%AD4*pi*ix%29+and+P%3D%28%28pi*ix%C2%AD-6%29%2F%28pi*ix%2B6%29%29%5E6+from+x%3D0+to+10

http://www.wolframalpha.com/input/?i=plot+abs%28P%2F%281-0.9*P%29%2BD%2F%281-%C2%AD0.01*D%29%29+where+D%3Dexp%28-%C2%AD2*pi*ix%29+and+P%3D%28%28pi*ix%C2%AD-6%29%2F%28pi*ix%2B6%29%29%5E6+from+x%3D0+to+10

http://www.wolframalpha.com/input/?i=plot+abs%28P%2F%281-0.9*P%29%2BD%2F%281-%C2%AD0.01*D%29%29+where+D%3Dexp%28-%C2%AD1*pi*ix%29+and+P%3D%28%28pi*ix%C2%AD-6%29%2F%28pi*ix%2B6%29%29%5E6+from+x%3D0+to+10