Developer builds 5-band parametric EQ in MATLAB using biquad filters and RBJ coefficients

A software developer has documented the design of a five-band parametric equalizer built entirely in MATLAB, using cascaded biquad filters derived from RBJ cookbook coefficients. The project relies on the bilinear transform to map analog filter prototypes onto the digital z-plane, with frequency prewarping applied to ensure accurate center frequencies. The implementation covers peaking, low-pass, and high-pass filter types, and includes a live response curve, rolling spectrogram, and pole-zero visualization. Written as a single class definition, the project avoids MATLAB's App Designer and requires no additional toolboxes beyond base MATLAB. The author also provides an honest audit of where the implementation diverges from its own user interface, including measurable frequency warping near the Nyquist limit.