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Calibrating / "Regulating" my midi keyboard - a DIY story
#2988195 06/05/20 03:31 PM
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Hi,

I recently noticed that my G5 seemed a bit low in velocity, so I thought I should investigate this and maybe correct the midi velocities through software. I could have googled if there's some smart way to do this but I didn't, that would be cheating smile

Solving the problem should have 4 steps:
1) Find a way to consistently strike the keys with a set of velocities
2) Record this to a midi file
3) Analyze the midi data to find the systematic variance
4) Create an offset value (or, if necessary, a tuning curve) for every key
5) Apply the correction
6) Re-measure and hope that this has had any effect.

So far I got to step three as follows:
1) I built a sophisticated device to strike the keys for me, between 12 and 20 times per key: https://youtu.be/561Sveu9IP8
2) Midi data was recorded with Reaper
3) Midi data was analyzed with R, see https://photos.app.goo.gl/iUhNU16JgiTXE7P39 for results

I think the results are pretty interesting:
a) I got quite consistent results, so I'd say the key striking device works okay.
b) There is less variability for higher velocities but I suspect this might be to a significant extent due to mechanical inaccuracies in the key striking device
c) The between-key systematic variability seems to be larger than I had hoped with the median value showing differences of 10 steps or more between highest and lowest observed (C5 and A5)
d) The difference in response to the difference in physical intensities is more worrying (C5 vs A5) because this requires a tuning curve per key and not just an offset to correct.

Obviously I've only done this for one octave and I have no apparatus for the black keys yet but anyway, I thought there might be other freaks that find this interesting.

I will probably create tuning curves and apply them through Reaper if I can figure out how to do this. I also need to get data for velocities around 20 and just under 127.

Has anybody done this before?

Re: Calibrating / "Regulating" my midi keyboard - a DIY story
Keybender #2988196 06/05/20 03:37 PM
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I like your hi-tech striking device 😁

But do you really need a pivoted hammer? Since it’s just gravity, isn’t it the same if you use some weight to put on top of the front part of the key and release it?


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Currently: Yamaha N1X, DIY hybrid controller -> Garritan CFX
Previously: NU1X, ES7, MP6, CA63, RD-700SX, CDP-100, FP-5, P90, SP-200
Re: Calibrating / "Regulating" my midi keyboard - a DIY story
CyberGene #2988203 06/05/20 03:47 PM
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Originally Posted by CyberGene
I like your hi-tech striking device 😁

But do you really need a pivoted hammer? Since it’s just gravity, isn’t it the same if you use some weight to put on top of the front part of the key and release it?

Well you know what they say... if all you've got is a hammer smile
Seriously though - i couldn't thing of another good way to consistently drop something a) on exactly the same spot and b) with the same inital velocity. Letting something go "suddenly" is tricky.
Also, I couldn't find anything else that is suitably heavy and just dropping the hammer onto the keys without guidance seemed like asking for some kind of injury or damage. Admittedly I didn't really look for anything else longer than about 30s.
Also, the pivoted hammer accelerates slightly faster than if you drop it. I don't think it matters here at all but I always found that fascinating.

Do you have an idea? I think there's a lot of room for improvement...

Last edited by Keybender; 06/05/20 03:49 PM.
Re: Calibrating / "Regulating" my midi keyboard - a DIY story
Keybender #2988212 06/05/20 04:04 PM
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These tools might help. There are other solutions.

https://forum.cockos.com/showthread.php?t=172630
https://viramor.com/csmidieq-midifx/
https://web.archive.org/web/20180228065838/http://platinumears.com/velocitycurvesm.html
https://web.archive.org/web/20190915061007/http://www.trombettworks.com/velocity.php

Re: Calibrating / "Regulating" my midi keyboard - a DIY story
newer player #2988217 06/05/20 04:13 PM
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Originally Posted by newer player
These tools might help. There are other solutions.

https://forum.cockos.com/showthread.php?t=172630
https://viramor.com/csmidieq-midifx/
https://web.archive.org/web/20180228065838/http://platinumears.com/velocitycurvesm.html
https://web.archive.org/web/20190915061007/http://www.trombettworks.com/velocity.php

I think all but the first one don't allow for PER NOTE velocity curves, right?


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