Pressure sensitivity is "bumpy" or inconsistent across device

Technical Support
1

Hello all!

I just received my morph a few days ago and have been testing it out. One thing I noticed immediately when I looked at the visualizer is that as I drag a finger across the device with steady pressure, the sensed pressure varies quite a lot, the spike going up and down rhythmically, almost like a flickering flame, as if there is a lot of inconsistency in the individual pressure sensors, or a problem with how the information is interpolated or something. This isn’t a shaky hand! I was very careful to ensure consistency. I even rolled a ball bearing across the bare surface to rule out my hand.

In practice, what this means is that if I have a patch in a synth where, for example, pressure is mapped to filter cutoff or gain, if I slide across the device, that pressure reading is jumpy and makes the sound level vary rapidly. It is very audible and pretty much ruins the device for my intended application. I had hoped to use pressure mostly instead of an envelope and also want to slide around with pitch bends and the like.

The problem doesn’t show up if I just vary pressure while holding a finger in one place.

I have a feeling that part of the problem is variations in the sensitivity of the individual pressure sensors. It seems that this needs to somehow be compensated for with calibration curves for each sensor, which sounds problematic with so many sensors!

I just observed that if I hold my finger in one place and vary the pressure through the range and then move my finger slightly to one side and do the same, there is a big difference in sensitivity between the two nearby locations. It is harder to push the spike all the way up in one spot compared to another.

I decided to do a more controlled test. I set the device up as a big XYZ pad and opened MIDIberry so I could read the pressure output. I taped a weight to a drum stick and put a small soft pad on the end. Then I rested the padded tip of the stick on the surface while balancing the stick vertically using a little wire loop loosely placed around the top the stick instead of my hand so that I don’t impart any vertical force. Then I moved the tip to various points, observing differences in the pressure readings. I found that they vary considerably from place to place. I might measure 126 (on a 0 to 127 scale) in one spot, and as low as 30 in another. The differences usually aren’t this large. That’s the maximal difference I measured. Differences in neighboring locations more commonly fall in the range of 20 to 30. This is still substantial variation!

Considering that this device is a grid array of pressure sensors, I imagine it isn’t just an issue of variations in sensitivity between individual sensors, but also a problem of “pixelation” or aliasing of the “image” of the sensed finger tip. For example, a sensed object sitting on the surface might span 3 sensors wide in one position and 4 sensors in a nearby position. And the overall pressure must be computed from a number of neighboring sensors. There are probably limitations in how well this can be done.

Is this an issue that affects all of these devices, or is there something wrong with mine?

I am also having problems with false touches and releases in one spot when using the Buchla Thunder overlay in the upper region of the E, F, and G “keys” on the left. I haven’t observed false touches with the drum or music production overlays. I haven’t yet received the piano overlay and so haven’t tested that. I would imagine that the pressure variations I have observed could have something to do with these false touches.

I also notice a lot of velocity variation, but given the pressure variation, it is obvious that this likely results from hitting in slightly different spots.

Thanks for your help!

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Can anyone confirm for me whether or not problem is present in all of these devices? Does yours do this too? Or is there something wrong with mine?

It is easy to test. Just open the visualizer and then drag a finger across while maintaining steady pressure. See if the spike stays at a constant height or wavers in height as you move.

If there is something wrong with mine, I need to get it replaced. If not, and this affects all Sensel Morphs, then I need to decide if I can live with it.

Thanks!

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With the visualizer, you’re seeing raw data. This is not what is transmitted when you use MIDI output, and that variation is not what you would hear when you apply the MIDI output to a synth.
If you are sliding across an overlay, there is going to be variation in pressure as you move across the bumps of the overlay. I would also imagine there is some friction effects, similar to rosin on a bow that would cause variation.
As for your exacting test, I spoke with one of our engineers:
“A weight gives a very different force profile on the Morph compared to fingers. We currently get the least variation with human fingers.”
There is some force variation that occurs across the device. Many programs offer aftertouch smoothing that can help reduce these variations.

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Thanks for the response!

When using fingers to play a synth like Serum, if I use pressure to modulate filter cutoff and then I slide to bend the pitch, the filter cutoff wavers up and down in just same way that I see the pressure reading varying in the visualizer. With high resonance especially, this is highly apparent. It is impossible to slide and keep a smooth or near-constant pressure value at the same time. This is without any overlay. And I can see the variations in the MIDI output with MIDIBerry. So it most definitely shows up in the MIDI output to a synth. It also shows up in variations in velocity readings when tapping in slightly different locations. I’d be happy to make a video if you are skeptical. If you test this and find that it doesn’t happen as I’m describing on another device, then perhaps mine has something wrong with it.

1 Like
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You have to do one thing. Reset the device and see if you see this problem again. I am using it for a lot of time and I have broke one and also bought a new one but never have I ever experienced this type of bumpy behavior. I guess you have some problem in your device. Does it happen from the beginning?, or it is happening all of a sudden?.

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Thanks for the reply, mariah!

When you suggest resetting the device, do you mean reinstalling the firmware? That’s the only option that I see. And I’ve tried that multiple times with no resulting improvement.

It’s interesting that you say you haven’t seen this behavior. With no further input from peter_sensel, I came to the conclusion that this must affect all of these devices and he just had no answer for me short of admitting to this defect.

When you open the visualizer and you drag your finger across the device with steady pressure, are you telling me that the spike doesn’t move up and down rhythmically as a function of the speed of your horizontal movement?

Maybe I should make a video of what I am seeing so that you can compare and see if there is any difference in what yours does. I’ll do that. Stay tuned…

I greatly appreciate your help!

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I made a quick video just showing how it behaves on the visualizer. No audio.
https://youtu.be/Bhc5kXMDcWw

See if yours behaves similarly. Thanks!

Edit: That link doesn’t work for me for some reason. You might have to just copy the URL and paste it in the address bar.

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Can anyone confirm or deny that this is typical behavior for these devices? Please? If it is typical, I’ve decided to just accept it and use the morph for what it’s still good at. It’s still worth the money, IMO, but is admittedly a little disappointing in several respects. But if this is abnormal, I need to get this thing replaced ASAP.

Thanks!

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Hey, sorry for for the delay here. We were short staffed last week due to the holidays. Confirming that this is normal.