Analyzing the Moog Polymoog Vox Humana Fixed-Formant Filter (as heard in Gary Numan's Cars)

Support this channel via a special purpose donation to the Georgia Tech Foundation (GTF210000920), earmarked for my work:    • [OLD] Support This Channel via a Special P...   0:00 -- Introduction 0:44 -- Sallen-Key filters 1:59 -- Setting up variables 5:01 -- Transfer function calculation 7:13 -- Cleaning up code 8:19 -- Wrong units! 8:39 -- The hairy edge 10:27 -- Plot for each filter 11:18 -- Summing filter outputs 14:17 -- Plot of summed outputs MATLAB/Octave code: r = 1E3 * [10 22 9.1 9.1]; c = 1E-6 * [0.01 0.022 0.01 0.01]; rg = 1E3 * [10 10 10 10]; rf = 1E3 * [10 15 18.2 19.2]; weight = 1.5 ./ [20 27 30 30]; wn = 1 ./ (r .* c); fn = wn / (2*pi) k = 1 + rf ./ rg; q = 1 ./ (3 - k) f = 10:10E3; w = 2*pi*f; s = j*w; hh = zeros(4,length(f)); for ii=1:size(hh,1), hh(ii,:) = -weight(ii) * k(ii) * wn(ii)^2 ./ (s .^ 2 + (wn(ii)/q(ii)) * s + wn(ii)^2); end %loglog(f,abs(hh)); axis tight hh_final = zeros(2,length(f)); hh_final(1,:) = hh(1,:) + hh(2,:) + hh(3,:); hh_final(2,:) = hh(1,:) + hh(2,:) + hh(4,:); loglog(f,abs(hh_final)); axis tight xlabel('Frequency in Hz'); ylabel('Magnitude');