IIR_Lab mini : a design help for digital audio filters

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This application helps you calculating IIR BiQuad filter coefficients basing on an intuitive approach.

You need to provide the sampling frequency (Fs), the cutoff frequency (say 200 Hz) and the Q (say 0.707). This way the program is able to calculate the recursive coefficients of the IIR BiQuad (the resonating cell).

You need to specify how much lowpass, bandpass and highpass you want in the transfer function. You can combine the three elements in any proportions. This enables you to generate all possible 2nd order transfer functions including pure phase shifters (allpass), notches, etc.

The five corresponding coefficients of the IIR BiQuad get then listed and written in a .txt file on your hardisk.

What you get as graphical result is the Bode Plot of the IIR BiQuad filter. The Bode Plot gets calculated using brute force : a signal gets generated at the input (a white noise), a FFT is then calculated both on this signal and the signal coming out of the cascaded filters. A triangular window is used as default.
 

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  • IIR Lab mini.zip
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  • 4000 Hz notch -6dB Q3.0.png
    4000 Hz notch -6dB Q3.0.png
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