Looking closer at positional sensing / hotspots

[Kabonfaiba]

Ever since MDM introduced the positional sensing readout, I've been re-evaluating my settings from the ground up.

I'm using a Diamond 12 inch snare, with centre mounted, cylinder style foam tower.

Problem: My position reverses on the hotspot. (Edge and Centre are labelled backwards inside MDM btw)

So I was trying different numbers for MinScan and I stumbled upon a a range (90~100ms) where by my positional sensing effectively reversed!

I drew an image to show my findings visually:

PosSenSettings.jpg

The summary is: neither option is perfect.

My default 50ms settings on Pos Level 2 or 3 has a hotspot, but the CC16 data is stable, deviation is low enough at all velocities and buzz rolls.

My 100ms setting is experimental, and it eliminates the hotspot. However, the centre zone pretty small. The CC16 midi is also less stable and might flip sometimes (probably because Megadrum has to pick from two competing waves I imagine) but it's 90% what the map shows.

It would be nice to have an option to reverse CC16 inside Megadrum though, or you could allow reversed High and Low values.

My experimental setting works in practice though, after reversing CC16 on your VST.

P.S. I also tried different latency settings from 15 (my default) to 100, but it had no perceivable effect on positional sensing.

What do you guys think?

Could the positional sensing algorithm be improved to eliminate the hotspot or is a hardware limitation with the technology?

[dmitri]

So I was trying different numbers for MinScan and I stumbled upon a a range (90~100ms) where by my positional sensing effectively reversed!

This sounds very strange to me. Once MinScan covers the whole first half wave for the algorithm it doesn't matter how much more you increase MinScan.
I doubt I can implement elimination of 'positional sensing hot spot' unless the central signal form is very different from rim signal. Btw, I tested it with Pintech 10" snare, Roland PD-125X and Drumtec 14" and don't remember seeing such hotspots with value reversal in the centre.
Have you tried to adjust the head tension or piezo foam pressure against the head?

[Kabonfaiba]

Hey Dmitri,

Yes I failed to mention, but I did experiment by adjusting the tension of the mesh head from low to very tight. It did affect the hotspot sensitivity, but not the PS midi.

I'm using a Drum-Tec design 2-ply. Furthermore, the natural sound of the mesh head as I hit, echo's what I see in the image, heard as a timbre / pitch change.

I haven't tried changing the mesh head to another brand or using 3-ply yet. I also considered maybe my piezo polarity might be wired the other way. I haven't really tried to adjust the height of my piezos either, since everything looks well adjusted and glued, and correct across all my toms as well.

I maybe shouldn't have said my positional sensing reversed, but maybe the rim area "expanded" beyond a usable range at 100ms, and therefore my center area became the new Low value, and Rim become the new High value. But MDM doesn't see it that way.

I have made usable PS snare from the settings but the dynamic range is much narrower than it could be, due to the fact the values alter over the mesh suface like on the image.

[SigiZ58]

I also experience the "reverse* positional sensing.

In fact, when you visualize the Roland Positional Sensing, you get a CC16 0 in the center and a CC16 7f near the rim. When my Megadrum positional sensing is halfway fine, I get similar values. What is strange for me, the the sliders in MDM are reverted, that means they show a Rim when CC16 0 is send and a Center when CC16 7f is send.

At first I was wondering and looking in the net I understood that it is nowhere clear defined what is Center and what is Rîm.

But I had to do sth else the days. Today now I read your topic and it is exact the same experience I have.

For me, The Roland definition is Master, as It works and sounds as it should in dependency from position. This means:

Center is 00h
Rim is 7fh

Salutations

[dmitri]

Just as Roland, MegaDrum sends CC 16 00h for center hits (if positional signal value is equal or above PositionalHigh), CC16 7fh for close to rim hits (if positional signal value is equal or below PositionalLow) and intermediate CC16 xxh values for hits between center and rim.

[SigiZ58]

Just as Roland, MegaDrum sends CC 16 00h for center hits (if positional signal value is equal or above PositionalHigh), CC16 7fh for close to rim hits (if positional signal value is equal or below PositionalLow) and intermediate CC16 xxh values for hits between center and rim.

But in this case MDM shows Position inverted (Sliders in Position "RIM" with value 00h) I checked the delivered values, but when I show the sliders and I hit the center, the slider is in Position RIM & vice versa.


Please check

Regards