A higher-order IIR filter built as a cascade of 2nd-order biquad sections. Choose a design Family — Butterworth (maximally flat), Chebyshev I (equiripple passband) or Chebyshev II (equiripple stopband) — and a Response: lowpass, highpass, bandpass or bandstop. Order sets the steepness (2 to 8), Frequency the corner or centre, Bandwidth the width of the band for the bandpass and bandstop responses, and Ripple dB the passband/stopband ripple for the Chebyshev families. An IIR design reaches a given steepness with far fewer coefficients than an FIR, at the cost of non-linear phase. The filter adapts automatically to the incoming signal's sample rate.
The analogue prototype for the chosen family and order is transformed to the digital domain and factored into a cascade of 2nd-order biquad sections, each advancing one sample-frame per tick to stay inside WaveWarp's sample-per-sample engine. Every parameter change re-derives the cascade.