analog like hp & bp filters

i realy like grobians filters and i would like to build a new synth with them but i also would like to have a hp and bp filter in this style. any hints on how to do? or is this feedback think just possible with lp-filters?

 

it should be possible, give it a try. the thing is it might not sounds as good, the feedback resonance, to my mind, sounds better at low LPF cutoffs. for HPF it might turn into ear-shattering shriek alt faster.

for a good example of a nice resonant LPF/HPF compo, make sure you check out the MS-20 clone by SolarX. its probaby my favorite Reaktor analog emulation, really top notch, and the filter sounds mean!

 

i agree with you about Solar X's MS-20, and i think i am correct in saying there is a touch of feedback in the filters.

sowari

 

OK I may sound a bit stoopid now, but what IS a grobian filter anyways? I rummaged through Carbon (in R4), and there are some modules in filter section that aren't used at all! Some stuff isn't even connected! Sounds like unfinished synth to me, but nonetheless it's a great sounding synth.

 

for sure it isn't that what i've expected. you ever hear the delay inside and the feedback screams terrible at high frequencies.
but i'll take a view at ms-20 clone. thanks for the hint.

@Dargon
i was talkin bout the filter from grobian that comes with electronic instruments 1. the kalaidon has some nice feedback filters too.

 

Grobian is part of the Electronic Instruments Vol 1 package.

http://www.nativeinstruments.com/index.php?id=reaktorelectronic&ftu=000c4da8dc9737b&flash=9

sowari

 

yes, carbon 1 does have the grobian filter i believe. i dont think its that the ensemble is unfinished, but i imagine mr daliot put quite a bit of work into that ensemble, im sure under the deadline he didnt have time to tidy things up as much as he should have.

 

I don't own EI 1, so I haven't heard the Grobian instrument. I'm guessing, from what's said before that what you're looking for is filters that have a noticeable ringing decay.

You can certainly do this with BP and HP filters as well as LP filters. In theory, any filter with very high Q should exhibit the ringing behaviour.

The ringning behaviour comes about as the radius of the poles of the filters become very close to 1.0. If the radius exceeds 1.0, then the filter becomes unstable, and you get uncontrolled feedback. At exactly 1.0, anything fed into the filter will not decay at all. You get interesting ringing effects when the poles take values like 0.998, 0.999996, etc. i.e. very close to 1.0.

Q settings directly control how close the poles lie to zero. The problem: mapping of Reaktor controls to Q may be less than straightforward. Most library filters would (I think) cap the maximum Q value, in order to prevent users from accidentally driving the filters into stability. They may cap the value, but cap it to a value that doesn't allow you to drive the poles close enough to zero. And you may not get the kind of fine-grained control you need at the top of the range, since very very small changes to the radius poles as they come close to 1.0 have a big effect on how long the filter rings. And a further complication: numerical accuracy issues come in to play, and they may drive the filter into instability slightly earlier than they should.

You could try the following: experiment with the maximum value of the Q control going into standard filters. And experiment with applying mappings of the Q value going into the filter: to get fine control over ringing, you will probably have to adjust the curve with some kind of exp-based or log-based function. e.g., if your control signal has range 1.0 (before mapping to Q takes place), then applying a function like y=1-(1-x)^10 (you'd have to experiment some) would give give you extended fine control at the top of the dial.

I have non-Reaktor code for a digital filter in which the resonance of the filter is specified by the height of the resonant peak above DC (soundfont filters specificy resonance this way). In this system, filters start to ring nicely once the setting gets to about 35db or so. Not sure that I can resurrect the code for it for use in reaktor, but -- in my mind -- it indicates that control mapping may play a significant role in getting the results you want.

 

man, you're just great! big thanks for your particular description.
i first tried to boost the q with feedback but i stoped that now since the result wasn't that what i've expected. now i try it with a peak eq before the filter and/or cascade filters. apparently 6 or 8-pole filters are that what i'm looking for but the q behavior is very importent too. so try to scale it with a high resolution at higher values. i'll give a reply if i found out any reasonable solution.