Use of Dual Filters: examples or tutorials?

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If you are going for physically-modeled sounds (either Karplus-like with comb filters or using regular resonant filters for a kind of modal synthesis), then the more filters you have available, the better.

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Rastkovic wrote: Sun Apr 28, 2019 10:36 am Another "trick"....

At times of mighty wavetable synths like Serum it's not really necessary anymore. But if you are restricted to basic waveforms for example, it's possible to use one of the filters to shape the harmonic content of a oscillator.

OSC 1 -> Filter 1 (Bandpass -> Keytrack = ON) -> Filter 2 (Lowpass)
OSC 2 -> Filter 2 (Lowpass)
That's a nice trick, thanks for sharing :)

Parallel band pass filters with a bit of resonance are a classic way of achieving formant-y effects. Lowpass and bandpass in parallel is quite interesting; with bandpass cutoff below the lowpass it acts as a different kind of "emphasis" to the LP resonance control and then when brought above the LP cutoff you get formant-like combinations.

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Besides Filterfreak 2, you can demo Volcano and The Drop. Or any other filter plugin that offers dual filters. Look at the presets.

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Kwurqx wrote: Tue Apr 23, 2019 12:44 pm - a Low pass + Low pass configuration. E.g. if you need a steeper slope (at the same cutoff). E.g 12 dB/oct + 12 dB/oct = 24 dB/oct. Or at different cutoffs the attenuate and/or boost at different places in the spectrum.
Even knowing how filters worked, for some reason this never mentally clicked until now. I've been annoyed that the "Infecto" filters in Spire were only available as 2-pole (since they're modeled after the Virus) but I never thought of just stacking the two in series. Thanks!
Kwurqx wrote: Tue Apr 23, 2019 12:44 pm Filters in parallel are often used to create some liveliness by effectively mixing 2 independent and different "layers". E.g. at slightly different cutoffs/resonance and/or different modulation rate/depth.
Second "Eureka" moment for me in just one post! I think the main reason I didn't really get it before was that I wasn't really thinking of them moving independently like that (although I've figured out that the dual filters in Omnisphere aren't truly independent the way Spire's are). I've been playing around with different envelope shapes for filters in parallel with some fun results.

I was going to be annoyed you thought I needed an explanation of what filters were for, but then you reminded me how useful a slightly different take on something you already know can be to fill in whatever gaps remained. Great post!
Rastkovic wrote: Tue Apr 23, 2019 5:41 pm typical setup for dubtechno chords. Two filters in series.....

1st filter: 12/24dB lowpass + envelope modulation
2nd filter: 12dB bandpass + lfo modulation
Not quite what you put here, but I tried an envelope-controlled 24dB lowpass and LFO-controlled 24dB very resonant bandpass in parallel (about 80/20 mix) and I really love the result. It gives a similar motion to an LFO on the cutoff but I still get the more defined attack too. Thanks for the inspiration!
CHOOS wrote: Sat Apr 27, 2019 12:26 pm Another application is creating multiple resonance spikes or 2 band-passed sounds and feed it into a distortion to get some mad sounds out of it.
I tried this on my moving bandpass sound I described above and I can't get enough of the growl.
mixtur.se wrote: Sat Apr 27, 2019 6:41 pm You’re definitely missing out
Oh yeah, I definitely was. I've been having so much fun now that I have a better understanding of it.
Kwurqx wrote: Sun Apr 28, 2019 9:49 pm One more usefull thing...

Many synth only offer either serial and/or parallel filters. Not all synths offer control over the filter input and/or output levels. A synth like Fathom offers a wet/dry mix per filter. A synth like Surge let's you set the filter mix/balance. This way you can have a pretty steep Low Pass filter at a low cutoff and still pass/mix higher frequencies (from the dry signal) too. Very usefull for strings and pads.
Good call! I can do that in Spire if I leave the second filter slot empty. I'm all about some pad sounds so I'll definitely have to try this out more.

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I'll add just one more thing. CHOOS mentioned (underused) Band Pass filters.

Another use for those is to use Band Pass filters as "Vowel" or "Formant" filters. Surprisingly you only need 2 peaks/filters. There are 3 peak variants/tables too, but most synths only offer "only" 2 filters per voice, so let's stick to that.

It's "simply" about creating peaks at specific intervals. The secret is in the "gap" between the peaks: the difference between the "cutoff" frequencies (F2-F1).

Before I start typing many words....I better refer to the Wikipedia page on Formants in general and specifically Average vowel formants.
https://en.wikipedia.org/wiki/Formant

If no Bandpass filters are available: some types of Low and High pass filters start to behave as Bandpass filters as resonance is increased, morphing towards an ever smaller bandwidth (and higher peak) until a single partial is achieved: self oscillation.

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You should maybe ask the Zebra for Examples. Or Zebralette, its cheap little Sister, if the almighty Omnisphere doesn´t answer you :/

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