On Tue, Nov 26, 2013 at 11:27:46AM +0100, Raphaël Mouneyres wrote: > as of multiband compresion for mastering purpose, i use 4 bands most > of the time, as the low spectrum needs special attention. > My first consederation based on your frequencies, is they leave > frequency gaps between bands. Ha, now I remember what I told Julien - which was exactly to do that. Depending on filter type and order, to obtain a flat response in the crossover region it is not always true that the filters should cross at the -3 dB points (and hence probably set to the same frequency). It is true for first order ones. One filter has +45 degrees phase shift at the nominal frequency, the other -45. Combining two signals at -3 dB and 90 degrees phase difference result in 0 dB, as required. This doesn't work for second order filters. They will have +/- 90 degrees phase shift at the -3dB frequency. If you set both filters to the same frequency and add the outputs, the region around that frequency will cancel. If you invert one of the two, the result will be +3 dB. To get the flattest possible response in the sum you have to set them to different frequencies. The result will never be really flat, but you can come close. If you want crossovers that exactly add up to a flat response you need filters like the ones used in zita-lrx. To answer Julien's question: just preserve the _ratio_ of the frequencies of the two filters that form a crossover. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
