Phantom rim hits

[dmitri]

This is confusing, but I guess MDM determines the zones based on the incoming MIDI data and the MIDI doesn't contain information about exactly which input and which zone was activated on Megadrum, so it cannot do any better than searching for the note number in the settings. Is that correct?

Correct.

[halifax30]

Okay, I'm trying to get this 35mm piezo and stick-piezo combo work as a head and rim sensor for my mesh-head snare. I was inspired by this post by privatex. I bought this type of stick-piezo: http://www.ebay.com/itm/221251338893.
My piezos are not built into any pad, yet. The 35mm piezo alone works as I expected. Problems start when I add the stick-piezo. I'm not sure whether the stick-piezo is faulty or I'm doing something wrong.
First I tested the stick-piezo. I arrived to the following settings:

• Gain = 6 - Quite high, because the stick-piezo is quite insensitive to hits with my fingernail.
• HighLvl = 356 - With this I get a full range of MIDI notes between 0-127.
• MinScan = 15 - I plugged the stick piezo into the microphone input of my PC and recorded hits as WAV files. I measured the length of the first half-wave and it was about 15 samples at 44.1kHz giving 0,3ms. Since the minimum value of MinScan is 10, I set it to 15 to be safe. I arrived to the MinScan value of the 35mm piezo in a similar way (145 samples = 3,3ms).
• Threshold = 30 - If I set it below 30, I start to get a constant stream of hits without touching the piezo. I guess, at that level MD starts to take noise as hits.

The problems

• When I leave the two sensors simply laying on my table every 30-60 second I get a rim hit (sometimes more) without anybody touching the piezo.
• When I hit the 35mm piezo, I get 1-2 rim hits for every head hit (see picture). It seems that in this situation the stick-piezo becomes extremely sensitive, which is weird. Why it is more sensitive to minimal vibrations getting to it via the cable (is this the reason?) than direct hits at the sensor? I noticed that lowering Gain of the stick-piezo to 2 almost fully solves this problem. But then the stick-piezo does not sense rim hits. When I only hit the stick-piezo I never get head hits.
• Even with these settings I still have to hit the stick-piezo quite hard to get hits, and every 4th-5th hit is ignored. Also, different parts of the stick have different sensitivity. It is also weird that rubbing my finger against the sensor back and forth registers several rim hits. So the sensor is sensitive to rubbing, but fairly insensitive to hits?? This is really weird.

Further info which might be useful

• Obviously, I don't know which part is the ceramic and which is the brass on this piezo. It came with a pre-soldered mono 2.5mm jack plug. I guessed that the wire connected to the jack tip is the ceramic, and the one connected to the sleeve is the brass. I'm not sure whether my problems are caused by incorrect wiring.
• My sensors are connected to Megadrum input 4 (Snare) through a PS board.

[airflamesred]

Personally, I would mount them in your drum and then configure. I don't see MD behaving incorrectly here and you will need to reconfigure once your pad is assembled anyway.
I have 35mm piezos on most of mine and a threshold of around 31 but also have a Triggera Krigg that needs a threshold of 50 or it misfires. A gain of 6 on mine will also misfire.
Not all piezos are born the same!

[halifax30]

Because of all the problems I decided to stop using stick-piezos as rim sensors for the time being and revert to 35mm piezos. I sticked the 35mm piezos to the inside of the drumhead and they work fine as rim sensors.
But I still plan to make a second try with stick-piezos. I will report back with my results. (It might take several weeks before I will have the time to do that.)