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BPF design as cascaded second order biquads

They are mostly identical (except for some small numerical errors). The SOS matrix is not a unique way to describe a filter. The same filter can be implemented with many different SOS matrices ...
  • 36.9k
0 votes

FFT, why my program works but doesn't?

FFT for filtering audio. Frequency domain filtering is mathematically quite complicated. Manipulating the spectrum directly typically results in lots of time-domain aliasing, which I'm guessing is ...
  • 36.9k
1 vote

Behaviour of difference equation does not match that of its z-domain transfer function

Probably the problems that you are seeing stem from trying to do sensible math on $7^{th}$-order polynomials without using insanely high numerical precision. There are some nearly-absolute dos and don'...
  • 10.7k
2 votes
Accepted

Behaviour of difference equation does not match that of its z-domain transfer function

If you want a discrete-time Butterworth filter you should design it in the discrete domain. If you use Matlab (or Octave), you can just use the function butter(). I ...
  • 82.9k
2 votes

What order of FIR filter is equivalent to an IIR filter for same design specifications and to get same magnitude response

This question could probably be flagged as a duplicate, but I'll answer here and let the mods decide if it's worth keeping. Dan Boschen on Fred Harris' Rule of Thumb. $$ N = \bigg\lfloor\frac{f_s}{\...
  • 2,993
1 vote

Filter IIR, 1/3 Octave Corner with 2 Octave BW

There is another way to do graphic EQ other than bandpass filters in parallel. You can use Parametric EQ in series where each band is spaced by $\frac13$ octave. Another reference is Oliver and Jot. ...
2 votes
Accepted

How to derive filter design (with parameters) from existing FIR weights

Sounds exactly like a description of the Matlab filter design tool, or the Python pyfdax tool. You place zeros close to the unity circle for attenuation; the placement of the zeros is all the ...

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