How to make steeper slope on bandpass filter?
How would I go about increasing slope steepness on a bandpass filter for more isolation around the cutoff frequency? Drambo only has a 12db bpf for now. I tried putting a hpf and lpf in series with the bandpass to shave of frequencies on either side of the cutoff, which worked reasonably well. But I'm gonna do this for like 30 bands, so maybe there's another way.
Any thoughts?
Comments
Put multiple BPF in series and increase the resonance of each. The steeper you want it for the same bandwidth, the higher the resonance value, the number of filters and the narrower the distance of center frequencies needs to be.
Think about a classic graphic EQ: A good design will just amplify the input signal when all sliders are put to the max because the band pass filters are tuned correctly.
Okay, so multiple bandpass in series, tuned to the same frequency. I’ll experiment with resonance depth and see where that takes me. Thanks for the tip!
On a side note, when the boss releases more analog filter models, hope there will be a 24db bpf and 24dp hpf in there as well.
No, spread the frequencies in equal distance! The higher the resonance, the closer the center frequencies have to be located between each other. Otherwise you'll just get a higher peak like with higher resonance.
Ideally you would use a 3rd party spectrum analyzer with good averaging and high enough resolution (the lower your center frequency the higher the FFT length must be) and a zoom feature.
BTW @aleyas, make sure you connect all BPF inputs (sorry, I should have said BPF in parallel!!) to the same source and mix their outputs like here:
One BPF:
Four BPF:
Filter settings:
Ah, I think we may have misunderstood each other. I'm trying to make an extremely narrow band, to more or less isolate the center frequency of the bpf. Maybe I used the terminology of slope steepness wrong? I tried the tuning you suggested, but there was too much bleed through among the filters.
I did manage to get rather good isolation with 3 serial bpf at the same frequency though, with resonance applied to only one filter. This gives pretty good isolation around the center frequency. I've got a bank of 12 of these (so 36 filters in all), which are parallel processing the input. There's a bit of thump across all filters with strong instrument attacks,, so I need to work on the input dynamics a bit.
Anyway, thanks for the help as always!! @rs2000
You're welcome!
It's always a good idea to include your original purpose in a question.
It's impossible to recommend the right tool without knowing that.
Indeed, I should have been more specific. Well, I’m toying around with making something like a resonator, using tuned bands excited by the input signal. If it turns out half way decent I’ll be sure to share it 🙂
Oh!
OK, in that case you'll have much more success with a number of peaking EQs.
Remember the analog vocoder patch I did a while ago?
With BPF modules, I just couldn't get there while the EQs did the job surprisingly well. And don't be afraid of insane boosts above +30dB.
yes I wondered why not just use parametric eqs ^^