Frequency Ranges of Filter Cutoffs

The Dave Smith Instruments Pro 2 Analogue Synthesizer

Moderator: Pym

errissa
Posts: 48
Joined: Tue Apr 08, 2014 3:59 pm

Frequency Ranges of Filter Cutoffs

Post by errissa » Tue Sep 09, 2014 3:51 am

Anyone happen to know the range of frequencies for the filter cutoffs of the two filters on the Pro 2? I couldn't find it documented in the manual or on the website.

I'm curious because when I sweep the filter down from 164 to 0 I find that C2 (65Hz) starts to attenuate at a filter cutoff value around 65. That seems a bit high. C1 (~33Hz) starts to attenuate at a filter cutoff value between 50-55. By the time the filter cutoff gets down to 20-25 little to no signal seems to get through. In fact, by watching a spectrogram as I sweep the filter down with resonance set very high I'd guess that at a filter cutoff of 30 is 20Hz. At 164 my guess is 20-22KHz. 20KHz at 164 seems OK, but 20Hz at 30 seems like an awfully low cutoff frequency with 30 steps of knob turning left to go. Can anyone confirm that this is correct?

User avatar
snowcrash
Posts: 519
Joined: Tue Jan 11, 2011 12:40 pm

Re: Frequency Ranges of Filter Cutoffs

Post by snowcrash » Tue Sep 09, 2014 8:07 am

I would greatly appreciate if the cutoff would get lower on the Pro 2 than on the previous models. On the Evolver series it's quite a pain to get the filter to fully close when multiple modulation sources are adding up. If the filter gets down to 20 Hz at a value of 30, that means there's a lot of threshold left to compensate for extensive modulation.

Also note, that MIDI note numbers are completely relative on a synth like the Pro 2, as each OSC can be tuned individually for a ridiculously huge range.

As for measuring: set the resonance of one of the filters to maximum and turn off all OSCs, that way you'll get a sine wave. You can easily measure the frequency of the sine wave with a proper analyzer plug in.
Desktop Evolver, Poly Evolver Keyboard, Minimoog Voyager OS, KORG MS20 Mini, Arturia Minibrute, Bass Station II, Roland SH101, Micromoog, Korg Wavestation SR, Elektron A4, Korg ESX/EMX, Hohner String Melody II, Yamaha AN1x...

errissa
Posts: 48
Joined: Tue Apr 08, 2014 3:59 pm

Re: Frequency Ranges of Filter Cutoffs

Post by errissa » Tue Sep 09, 2014 1:00 pm

snowcrash wrote:I would greatly appreciate if the cutoff would get lower on the Pro 2 than on the previous models. On the Evolver series it's quite a pain to get the filter to fully close when multiple modulation sources are adding up. If the filter gets down to 20 Hz at a value of 30, that means there's a lot of threshold left to compensate for extensive modulation.
Good point.
Also note, that MIDI note numbers are completely relative on a synth like the Pro 2, as each OSC can be tuned individually for a ridiculously huge range.

As for measuring: set the resonance of one of the filters to maximum and turn off all OSCs, that way you'll get a sine wave. You can easily measure the frequency of the sine wave with a proper analyzer plug in.
Right. That's how I measured it except I didn't turn off Osc 1. Even so, with the resonance set high, it was easy to follow the resonant spike on a spectrum analyzer as I turned the filter cutoff knob.

I'm mildly bothered by how obviously the filter cutoff steps, especially with resonance. Filter sweeps with modulation are very smooth but I would like the filter cutoff knob to adjust the cutoff more smoothly. 134 steps between 20 and 20000 is not enough.

User avatar
snowcrash
Posts: 519
Joined: Tue Jan 11, 2011 12:40 pm

Re: Frequency Ranges of Filter Cutoffs

Post by snowcrash » Tue Sep 09, 2014 4:06 pm

That's actually true for any digitally controlled synth I know. Maybe except the modern Moogs, as they have a very very high resolution for parameters. Still when it comes to slow manual filter sweeps I found out only fully analog gear is sufficient.
Desktop Evolver, Poly Evolver Keyboard, Minimoog Voyager OS, KORG MS20 Mini, Arturia Minibrute, Bass Station II, Roland SH101, Micromoog, Korg Wavestation SR, Elektron A4, Korg ESX/EMX, Hohner String Melody II, Yamaha AN1x...

User avatar
Strange Quark Star
Posts: 169
Joined: Fri Jul 03, 2009 6:57 pm

Re: Frequency Ranges of Filter Cutoffs

Post by Strange Quark Star » Tue Sep 09, 2014 9:59 pm

snowcrash wrote:That's actually true for any digitally controlled synth I know. Maybe except the modern Moogs, as they have a very very high resolution for parameters. Still when it comes to slow manual filter sweeps I found out only fully analog gear is sufficient.
That's my major gripe with people asking for MIDI control/patch memory of analog synthesizers; unless you pay Moog prices for 12 bit DA resolution you will get stepped parameters and a separation from the circuitry, sometimes not even permitting simultaneous sweeps of multiple parameters. I know the Voyager and Little Phatty support high-rez digital potentiometers, but do the Sub Phatty/37? It's only mentioned in the SP manual for MIDI transmission of patch parameters, not the panel potentiometers themselves.
Prophet '08 Serial № 01369
Yamaha DX7 II FD E!, RX7 | Roland Ⅾ-50 | Korg MS-20 mini, microKORG, Volca Beats | Moog Etherwave Plus | Kawai K-5 ATX
--
YT: http://www.youtube.com/StrangeQuarkStar
SC: https://soundcloud.com/strange-quark-star

errissa
Posts: 48
Joined: Tue Apr 08, 2014 3:59 pm

Re: Frequency Ranges of Filter Cutoffs

Post by errissa » Tue Sep 09, 2014 10:31 pm

Strange Quark Star wrote: That's my major gripe with people asking for MIDI control/patch memory of analog synthesizers; unless you pay Moog prices for 12 bit DA resolution you will get stepped parameters and a separation from the circuitry, sometimes not even permitting simultaneous sweeps of multiple parameters. I know the Voyager and Little Phatty support high-rez digital potentiometers, but do the Sub Phatty/37? It's only mentioned in the SP manual for MIDI transmission of patch parameters, not the panel potentiometers themselves.
I just tested the Sub37 and it's smoother than the Pro-2 but I doubt it's got 12bits of resolution on the panel potentiometers. Still sounds a bit 'steppy' to me.

I don't understand why so many digital synths continue to use 0-127 and 0-255 as ranges for parameters when internally they don't have those limitations. Though I supposed if we got high resolution panel controls then we'd be complaining that we can't match over MIDI what we can do on the front panel!

User avatar
Strange Quark Star
Posts: 169
Joined: Fri Jul 03, 2009 6:57 pm

Re: Frequency Ranges of Filter Cutoffs

Post by Strange Quark Star » Tue Sep 09, 2014 10:44 pm

Even MIDI can handle higher resolutions, no problem, with MSB and LSB messages, so you'd need at most twice the MIDI communications.
I like MIDI as much as the other guy, but it really needs an overhaul or be superseded altogether; sync issues, clogging up when sending as much as polyphonic aftertouch… I just can't accept the fact that my cheap old mixer can send 16 tracks of 24 bit, 96kHz audio over USB 2.0 with no issues when new and advanced synthesizers are still mostly limited (by MIDI?) to 7 or 8 bits of parameter resolution and a very low frequency.
Prophet '08 Serial № 01369
Yamaha DX7 II FD E!, RX7 | Roland Ⅾ-50 | Korg MS-20 mini, microKORG, Volca Beats | Moog Etherwave Plus | Kawai K-5 ATX
--
YT: http://www.youtube.com/StrangeQuarkStar
SC: https://soundcloud.com/strange-quark-star

Martin3
Posts: 53
Joined: Tue Oct 01, 2013 2:16 pm

Re: Frequency Ranges of Filter Cutoffs

Post by Martin3 » Wed Sep 10, 2014 12:36 pm

Hi,

hi they are in tune with the notes thats why these steps are important, if you want "more Number" just use modmatrix(modwheel) it will smooth things.
For 1:1 scaling use Key amount +64.

Hope this helps,

Martin

blewis
Posts: 219
Joined: Sun Sep 29, 2013 7:11 pm

Re: Frequency Ranges of Filter Cutoffs

Post by blewis » Thu Sep 11, 2014 5:19 pm

I don't get Filter1's cutoff either. Seems the lower 25% of range passes lower than audible freqs.

I also can't seem to use Filt2 in HP to boost the bass as I heard on P12 you could do this with HP resonance cranked. The lowest freq of Filt2 is too high for doing this.


DSI support has said this is normal. I have calibrated the filters multiple times.

User avatar
BobTheDog
Posts: 1156
Joined: Sun Nov 20, 2011 8:49 pm

Re: Frequency Ranges of Filter Cutoffs

Post by BobTheDog » Thu Sep 11, 2014 10:31 pm

blewis wrote:I don't get Filter1's cutoff either. Seems the lower 25% of range passes lower than audible freqs.

I also can't seem to use Filt2 in HP to boost the bass as I heard on P12 you could do this with HP resonance cranked. The lowest freq of Filt2 is too high for doing this.


DSI support has said this is normal. I have calibrated the filters multiple times.
I don't have a P2 but can't you use DC offsets in the mod matrix, you can lower the frequency with a negative value.

blewis
Posts: 219
Joined: Sun Sep 29, 2013 7:11 pm

Re: Frequency Ranges of Filter Cutoffs

Post by blewis » Thu Sep 11, 2014 11:13 pm

Good tip Bob!

Yes, I can lower the cutoff of F2 in HP mode using a DC offset in the mod matrix. Finally can hear the HPF boosting the bass. I will note I have to _drastically_ offset it - like by > -100 to get it to be really low.

I don't think anything can be done for F1 though. From 0 to 40 there is just almost nothing audible passing through when it's used by itself.

Thanks man. More and more I'm finding it interesting that we can, get this, modify stuff in the mod matrix if we don't like it. :-)

errissa
Posts: 48
Joined: Tue Apr 08, 2014 3:59 pm

Re: Frequency Ranges of Filter Cutoffs

Post by errissa » Fri Sep 12, 2014 2:27 pm

blewis wrote:Good tip Bob!

Yes, I can lower the cutoff of F2 in HP mode using a DC offset in the mod matrix. Finally can hear the HPF boosting the bass. I will note I have to _drastically_ offset it - like by > -100 to get it to be really low.

I don't think anything can be done for F1 though. From 0 to 40 there is just almost nothing audible passing through when it's used by itself.

Thanks man. More and more I'm finding it interesting that we can, get this, modify stuff in the mod matrix if we don't like it. :-)
What do you think the range of filter 2 is on your P2? On mine I had a weird problem where the cutoff frequency of filter 2 would decrease from 164 -> ~85 then starting increasing again from 85->0. Recalibrating fixed it and now the filter 2 and filter 1 cutoff ranges seem to match. I'm able to get HPF bass boost without using the DC offset. What frequencies are you trying to boost? I'll try it it on mine.

blewis
Posts: 219
Joined: Sun Sep 29, 2013 7:11 pm

Re: Frequency Ranges of Filter Cutoffs

Post by blewis » Sat Sep 13, 2014 8:14 pm

Starting with a basic patch from the Global Menu. I set OSC 1 Pitch to C1. Crank the Sub. Turn up OSC 2 to max at C2.

With Filter 2 enabled and set fully to HP and the cutoff at 0 and the resonance at MAX, I see a peak of about 100Hz on Logic's EQ analyzer. I can DC offset the filter lower, but 100Hz is the lower the F2 cutoff knob will take me.

I just re-calibrated the filters. I think I've calibrated them maybe 10 times in the last couple of weeks hoping this behavior would go away.

More confusing/annoying to me is Filter 1. To get a resonance hump at 100Hz with the same slightly modified basic patch, I have to turn the cutoff up to 80 - that 50% of the entire range of the filter knob! Again 0-40 and total inaudible - confirmed by Logic's analyzer showing _nothing_ in those ranges.

Is this how your filters are working?

With these cutoffs, seem like the "link filter" button strange since these filter's cutoff are so drastically different than one another. With F2 in HP - linking F1&F2 gets me audible stuff at around 85 centered at 400Hz. It's completely uninteresting and wimpy and the F2 in BP mode can capture way more bass in the lower registers. Again, this would have to be adjusted with the DC offset to create a bandpass/notch setup, but I expected the default to be tuned to be somewhat useable.

Does this sound right to anyone who owns a P2? I've never really had to study a synth's filters so much to understand their operating ranges - but I've not really had this many options either - which is a good thing!

errissa
Posts: 48
Joined: Tue Apr 08, 2014 3:59 pm

Re: Frequency Ranges of Filter Cutoffs

Post by errissa » Sat Sep 13, 2014 9:17 pm

^

That doesn't sound like how my P2 is working. The filter 1 and 2 cutoffs on mine seem to match closely post-calibration.

I'll try replicating exactly your setup tonight when I'm home.

errissa
Posts: 48
Joined: Tue Apr 08, 2014 3:59 pm

Re: Frequency Ranges of Filter Cutoffs

Post by errissa » Mon Sep 15, 2014 12:35 am

I got a chance to try what you described below and I get a different result.

For me, with a Filter 2 cutoff of 62-ish I got a resonant peak at 100Hz. At a Filter 2 cutoff of about 40 I get a peak around 30Hz. These results are consistent with my Filter 1 which at a cutoff of 66-ish peaks at 100Hz. I certainly didn't need a DC offset. So, my Filter 1 and 2 don't match exactly in this test, but I wouldn't necessary expect them to given the different filter slopes.

Regarding the low end of the of the Filter cutoff range... I do get a signal below a setting a 40 on both Filter 1 and Filter 2. It's hard to tell for sure but I'd guess that a setting of 40 on both filters corresponds to around 30Hz. A setting of 30 is almost definitely 20Hz or below. At the same cutoff settings, it seems that Filter 1 is consistently a few Hz lower but not by too much.

Linking the filters gives consistent results in my opinion.

Based on my experience I'd have to say that something is not right with your P2. I'd love to hear from other P2 owners on this.
blewis wrote:Starting with a basic patch from the Global Menu. I set OSC 1 Pitch to C1. Crank the Sub. Turn up OSC 2 to max at C2.

With Filter 2 enabled and set fully to HP and the cutoff at 0 and the resonance at MAX, I see a peak of about 100Hz on Logic's EQ analyzer. I can DC offset the filter lower, but 100Hz is the lower the F2 cutoff knob will take me.

I just re-calibrated the filters. I think I've calibrated them maybe 10 times in the last couple of weeks hoping this behavior would go away.

More confusing/annoying to me is Filter 1. To get a resonance hump at 100Hz with the same slightly modified basic patch, I have to turn the cutoff up to 80 - that 50% of the entire range of the filter knob! Again 0-40 and total inaudible - confirmed by Logic's analyzer showing _nothing_ in those ranges.

Is this how your filters are working?

With these cutoffs, seem like the "link filter" button strange since these filter's cutoff are so drastically different than one another. With F2 in HP - linking F1&F2 gets me audible stuff at around 85 centered at 400Hz. It's completely uninteresting and wimpy and the F2 in BP mode can capture way more bass in the lower registers. Again, this would have to be adjusted with the DC offset to create a bandpass/notch setup, but I expected the default to be tuned to be somewhat useable.

Does this sound right to anyone who owns a P2? I've never really had to study a synth's filters so much to understand their operating ranges - but I've not really had this many options either - which is a good thing!
Last edited by errissa on Mon Sep 15, 2014 4:32 am, edited 1 time in total.

blewis
Posts: 219
Joined: Sun Sep 29, 2013 7:11 pm

Re: Frequency Ranges of Filter Cutoffs

Post by blewis » Mon Sep 15, 2014 12:47 am

DSI support said my Filt1 was expected behavior.

I'll send them the same question regarding Filt2.

Last week for me to decide to return it or not and the differences we are seeing in Filter response is leaving me uneasy.

Something doesn't feel right to me.

blewis
Posts: 219
Joined: Sun Sep 29, 2013 7:11 pm

Re: Frequency Ranges of Filter Cutoffs

Post by blewis » Mon Sep 15, 2014 11:49 am

Errissa, I forgot to says thanks for taking the time to check it out for me. Thanks.

errissa
Posts: 48
Joined: Tue Apr 08, 2014 3:59 pm

Re: Frequency Ranges of Filter Cutoffs

Post by errissa » Mon Sep 15, 2014 1:12 pm

Filter 1 may be within the expected tolerances but it sure seems like your Filter 2 is off. I would definitely ask DSI about it.
blewis wrote:DSI support said my Filt1 was expected behavior.

I'll send them the same question regarding Filt2.

Last week for me to decide to return it or not and the differences we are seeing in Filter response is leaving me uneasy.

Something doesn't feel right to me.

paaants
Posts: 3
Joined: Wed May 04, 2016 1:16 am

Re: Frequency Ranges of Filter Cutoffs

Post by paaants » Wed Jun 01, 2016 11:48 am

Any further info on the frequency range of a healthy filter 2? Did you ever ask DSI support about it, blewis?

blewis
Posts: 219
Joined: Sun Sep 29, 2013 7:11 pm

Re: Frequency Ranges of Filter Cutoffs

Post by blewis » Wed Jun 01, 2016 11:46 pm

i think I responded on Gearslutz. This topic is showing up on all forums today.

Post Reply