Equalizer's Coefficients (IIR Type) Low shelving, High shelving, Peaking and Notch filters are serialized. Click "Design->Response" to design and draw. Then click "Coeffs" to get coefficients. Clicking each component changes its characteristics. Frequencies are normalized. i.e. Sampling Frequency is 1.0, Nyquist Frequency is 0.5. Equalizers of IIR type normally consist of serialized Biquad (2nd order IIR) filters. See fig. 1. Please be careful of the polarity of b1 and b2 are inverted on the actual design. fig. 1. Mathematical model of Biquad (2nd order IIR filter) If this applet looks something weird, please reload it. Updated on 05 August, 2003 (ver1.0).