Which piezo works best in DIY edrums with Megadrum?

[airflamesred]

Answers will vary for sure. Many other things to consider, placement, glue, position etc.

[ignotus]

Sounds like it has a 27 mm piezo for the head and a 35 mm for the rim. The safest bet are Murata brand piezos. Whatever you do, just avoid cheap Chinese ones.

[ignotus]

You want the brass ones. As for resonant frequency, I don't really know what Roland and others use, but the piezos I buy are 4500 kHz and work fine. My uneducated guess is that the resonant frequency doesn't matter that much and is more relevant when using the piezo as a buzzer, not a sensor.

By cheap Chinese, I mean the piezos they sell on Aliexpress and ebay and don't state the brand nor any technical details about them beyond their diameter.

If you have the positional sensing board, you don't have to worry about the first half wave polarity - that's what it's for. And if you don't have it, positional sensing will be a struggle anyway. And a voltage divider shouldn't be required either.