These are the formulas you want: https://webaudio.github.io/Audio-EQ-Cookbook/Audio-EQ-Cookbook.txt https://webaudio.github.io/Audio-EQ-Cookbook/Audio-EQ-Cookb

These are the formulas you want: https://webaudio.github.io/Audio-EQ-Cookbook/Audio-EQ-Cookbook.txt https://webaudio.github.io/Audio-EQ-Cookbook/Audio-EQ-Cookbo... They are the classic IIR biquads. If you want steeper filters, just run multiple equal filters in series (high-order IIRs are prone to numeric instability). A more modern formatted version exists at e.g. https://www.w3.org/TR/audio-eq-cookbook/ https://www.w3.org/TR/audio-eq-cookbook/ .