2013/3/19 Justin Chudgar <justin at justinzane.com>: > I've created a module to ensure that only low frequencies are sent to devices > at the end of an "lfe"/"subwoofer" channel. This module allows the user to > select the master channel, the low pass cutoff frequency (aka corner freq, -3dB > freq) and the number of filter poles. Sorry, I cannot sign off this filter implementation. First, the filter currently fails the "attenuation must be 3 dB at the cut-off frequency" test that all Butterworth filters must pass. Second, Q=sqrt(2) is only valid for a 2nd order Butterworth filter. So, please, start over and implement only a 2nd order Butterworth filter (in both lowpass and highpass versions), as that's the only type of filter you would need for the LP-4 crossover. Or, go with a simple RC filter and implement an LP-2 crossover from them. A good article for LP-4 (unfortunately, only incompletely translated from Russian into English) is at: http://ac3filter.net/wiki/Bass_redirection_(math) -- Alexander E. Patrakov
