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Alex,
> The only problem that remains is the fact that the critically damped
> filter blows up below a certain value of L. For the 2-pass critical
> damping filter, it blows up when L<=4.6, and starts ringing around L=9.2,
> so you wouldn't want the length to be less than 9.2. There's some
> adjustment that needs to be put in the formula somewhere but I haven't
> figured out what it is.
>
I think the problem is here:
Wc = tangent(180 * cc / length); {pi = 180 degrees in EL}
at pi or n*pi (180 or n*180) the tangent becomes 0 and then everything else
hereafter becomes zero too:
K2=0, a0=0, a1=0, a2=0, b1=0.36 and b2=0.64
This happens at length 2.3 with passes = 2 => cc = 2.3
Between 4.597 and 4.598 the tangent switches from -infinite to +infinite
But here:
Length: 4.598 Pass: 2 cc: 2.3 x: 1.57 Wc: 35892.29 aa: 2 K2: 1288256655.09
a0: 1 a1: 2 a2: 1 b1: -2 b2: -1 sum(a..b): 1
the coeficients stay as in the line above.
Calli
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