so, here's the biquad verision of the 8 point average filter
I was actually more interested in the raw filters and I could get there with the biquad version by converting the coefficients to poles/zeros. All I did now was the opposite conversion to make the biquads.
but yeah, I fried my brains a bit to be able to make the biquad for the 4 average filters, it was all about trying to find a clever solution, but then I got stuck by trying to follow the same line of thought to make other poin averages like 8...
So let me see if I got it straight. All you need to do is divide the circle in the number of points and you know where the zeros are. For instance, a 2 point average just divide 360 / 2 and you have 180º
8 point average 45º - 90º - 135º - 180º - 225º - 270º - 315º
So, a 3 point average filter is 120º and 240º
right?