Forums > MaxMSP

Modulate filter frequency

December 29, 2011 | 1:34 am

Hi
I would like to moulate the cutoff of a filter created with the filterdesign + cascade method.
Now of course thats easy with floats but there appear clicks.
I thougth it must be possible to modulate it with a signal, but couldn’t figure out how?
Thanks for any pointers!


December 29, 2011 | 3:19 pm

Is this not possible? I must be overlooking something.. please..



Eav
December 29, 2011 | 5:38 pm

Hi,

Not an expert, but i think you can find everything you need right here: http://cycling74.com/2008/07/15/lfo-tutorial-1-the-zen-of-the-silent-patch/

good luck


December 29, 2011 | 5:45 pm

Thanks. erm,
The problem is really that i don’t see a way to use filterdesign(which hasn’t existed when this great tutorial was written) and change the cutoff frequency at sample rate.
Thanks anyway, still hoping that i miss something here.
cheers


December 29, 2011 | 6:16 pm

There are a couple of things here – the first one being (if I recall correctly) that the dictionary stuff that filterdesign passes to the cascade~ object is filter coefficient-based – so there’s not going to BE a "cutoff frequency" value, as such. That’s always been true for the cascade/biquad objects, attested to by the existence of the tried and true filtercoeff~ object from long ago. That said, it’s pretty clear that the filtercoeff~ object does allow for signal-rate manipulation, in which case I’d wonder if perhaps mucking about with the dictionary data structure being passed to the cascade~ object might be one way to approach the problem. I wouldn’t be surprised that it might be hairy, but you *do* have access to the dictionary data structure that the filterdesign object is pumping out via the dict object, don’t you?


December 29, 2011 | 6:29 pm

thanks. wouldn’t it be great if one could design arbitrary filters and having a filtercoeff manipulation object to modulate the cutoff?
I mean i really think i understand the problem here but it seems like i would have to kind of reverse engineer the filterdesign stuff.. maybe i am wrong here but … consider it a feature request maybe.


December 29, 2011 | 6:46 pm

Thinking about it again, i cant understand why this isn’t somthing a lot of people would like to be able to do in a fast and simple manner. Filterdesign would just get so powerful. doesn’t one need filters that don’t click when the cutoff is changed most of the time?


December 30, 2011 | 8:38 pm

i agree. the crackling when adjusting frequency is so messed up….


December 30, 2011 | 10:55 pm

I agree that this could use some options for at least getting click-free filter cutoff movements.

in the meantime, check out Peter McCullough’s filters here:

http://cycling74.com/author/petermccullochgmailcom/?kme=forum+user+tool+count+click

the moog one is particularly tasty, and eminently hackable! :)


December 31, 2011 | 7:02 pm

but you wont get click free movements anyway with a biquad – as soon as people have the option to use signals to control a biquad, they are in danger of explosions more than before. :)

maybe i dont get the original post, but i think the best was is to convert numbers to signal for a biquad using ]line~ 35] …

-110


December 31, 2011 | 10:04 pm

Maybe i wasn’t clear enough..sry.
Controlling biquads cutoff is no problem at all, since it works click-free with filtergraph or even better, one can use an "audio" signal for the filtercoeff- objects cutoff (don’t know if this exists in max 4 since you are 4 roman right?btw thanks for the remapping abstractions!)
My problem is kind of max 6 specific since i miss the possibility to change the cutoff of the new filterdesign object without clicks, which makes me sad.


January 1, 2012 | 5:05 am

i usually use a hidden filtergraph when i need "filtercoeff" in OS9 – but there is also that third party double-precision hr.filtercoeff~ MSP object – which does the same than the cycling one from max 4.5 and above – if you just leave the second output pair alone.

that, and the percolate MSP mtof~ belong to the few third party objects i accept.

seems i was missing the difference between "filterdesign" and "filtercoeff", maybe you should type louder. :)

-purist 110


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