On Sat, Mar 27, 2010 at 05:15:18PM +0100, fons@xxxxxxxxxxxxxxx wrote: > On Sat, Mar 27, 2010 at 02:45:18PM +0000, Folderol wrote: > > > What! Are you telling me that going round the edge of a CD with a felt > > tip pen *doesn't* improve the 'clarity'? :D > > Depends on the price of the felt tip pen. > > Regarding the 'feel' of filters, I've put up some examples > on <http://www.kokkinizita.net/linuxaudio/paramfilt.html>. > > These are three examples of a parametric filter set to > 1 kHz, fixed 'bandwidth' and gain between -15 and +15 dB > in steps of 5 dB. The curves for +15 dB are identical for > all three. > > If you compare Type 1 and Type 2, it's easy to see that > the two would 'feel' quite different if you turn the gain > knob. Most filters you'll see in practice will be somewhere > in between these two. For example my Ladspa filter plugin > is such a compromise, visually somewhat closer to 1 than > to 2. > > Type 3 looks quite odd, but it is in a sense the most > 'natural' of all three: it corresponds to a variable amount > of a *fixed* bandwidth (i.e. independent of gain) 2nd order > resonance being added or subtracted. Again this 'feels' > different. > > Now the DSP code used to produce these curves is identical > for all. It has three internal parameters, c1, c2, g, and > the only difference between the three forms is in the way > that the three 'user' paramters Frequency, Bandwidth and > Gain are mapped to the internal ones. Given a certain curve > (i.e. values for c1, c2, g) all three can produce it. > > So this is in fact three time the *same* filter, just > 'presented' differently. > None of this really addresses the difference in *sound* of these supposedly-"magical" filters. But Google turned this up, which I found interesting: http://www.playgroundstudio.com/blog/?p=60 Has anyone tried emulating these Neve filters in software using LADSPA? Anyone want to? (um, hi Fons!) -ken _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
