Hello

I am currently trying to transfer some quadraphonic works performed with Pure Data to stereo (for CD burning)

The idea is to program a dual-outlet~ abstraction that performs fake quadra spatialization as a psychoacoustic illusion, using tunable doppler, pan and filtering effects. (btw is there such external for Pd ? for example under Max there is ircam's Spat or GMEM's holo-spat)

Unfortunately I have some problems with the filtering section :

*1* Q factor problem How is it possible to control the Q factor (slope) of the hip~ and lop~ objects ? The only solution I found was to use a series of filters (more filters -- > better Q). There must be a reason why there is no "Q" parameter like the 3rd inlet of "bp~".

*2* Spectrum of hip~ The spectrum of a hip~-processed signal (noise for example) looks strange : it seems impossible to cut ALL the frequencies, even if the cutoff is close to 20000 Hz (if you try this, turn your monitors down) : indeed, the energies of high frequencies are getting higher and higher if the cutoff increases, and only a few low frequencies are actually cut.
Is hip~ really different to lop~ (the spectrum of lop~ looks "normal") ?

*About (classic) low/high shelving I need this for my patch I have programmed low and high shelving abstractions, using hip~ and lop~, but these are quite complicated (difficult to add or remove some frequencies with the SAME parameter) and don't sound very well (due to the filter problems I mentionned above).

It's easy to use an FFT-filter (multiplication between the spectrum table and a drwan cutoff table), and the quality is far better, but there must be a simpler solution using only classic low and highpass filters. Any idea ?

About Internet externals, I found something called "lowshelf", but I don't know at all how it works. Please tell me if there is a help file or a readme elsewhere, or at least what the inlets and outlets are...

Thanks a lot

J