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Reducing a piezo's sensitivity

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  • Reducing a piezo's sensitivity

    I'm using an Alesis 12" realhead for my snare. The problem is that it takes only a light hit on the rim to make the rim piezo output its maximum. Any ideas on how to make it less sensitive and get a bit more of linear response?

    Simply reducing the sensitivity in the module just means light hits still max out but at a lower volume. I think putting resistor on the piezo will have the same result too.

    My theory is that I need to reduce the amount of force getting to the rim piezo so light hits result in low output and hard hits result in higher output.

    Does anyone have any advice or experience with this? Could I isolate the rim piezo with foam?

    thanks!

    Gord

  • #2
    Perhaps using an exponential curve setting in the module will help? This would have the effect of desensitizing the module to lighter hits, but still allow stronger hits to register with high volume. Just a thought.......
    Mapex M-Series 6 pc. kit, Megadrum-56PS, RME Babyface Pro, DIY super-strut cross bars, Quartz piezos & cones, DIY rim silencers, 682drums black mesh heads, Pearl MFH reso heads, Roland VH-11, FD-9, 1xYamaha PCY-135, 4xPCY-155, Lenovo W541 laptop with win10 & Addictive Drums 2, Simmons DA-200S drum amp.

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    • #3
      Using a different response curve does help a bit--the light hits are bit more quiet. However still a moderate rim hit easily maxes the velocity to 127.

      I tried moving the rim piezo to different spot on the drum body. This does't really help. The rim gets either less or more responsive depending on where you position it. However, it still has a limited dynamic range.

      I'm wondering if there are piezo's with larger dynamic range. Does anyone have any experience with that?

      thanks,
      Gord

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      • #4
        No, never use curves to correct a physical issue. Either add some resistors to your piezo till it gives out the right response desired, or have a fiddle with the internal foam. You can always mount the edge piezos on some EPDM foam, like the 1/2mm stuff, to slightly dampen the vibrations. You may also wanna check the vibrational connection between the head and rim piezo - if it's not in the sweet spot your module wants then you're gunna get loads of rim click and barely ever a rim shot, or vice versa.

        For larger dynamic range try different piezo sizes. Hard to 100% confirm that a smaller piezo would help, but they usually are less sensitive to vibrations given they are smaller, though this could have an effect of making it so the initial hit to trigger and edge is much harder, and that you peak out too quickly rather than having that range of volume and attack that I believe you are looking for.

        Take a picture of the inside of your drum and I'm sure people can help more when it's visualized.

        My feeling is that this is a physical issue, not electrical. It's very similar to the issue I had on my OB-6 keyboard where the aftertouch is too strong - adding a resistor would just increase the base value to hit the note rather than widening the response area which needs some physical alteration to the foam. Otherwise you get into a lot more complex electronics to widen the response of a circuit prior to it reaching it's sound source/module.
        Last edited by Myrk-; 12-30-17, 04:38 AM.

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        • #5
          Get yourself a 20k (or similar value) pot. Piezo brass and cable sleeve to left pin (knob facing you), piezo ceramic to middle pin and right pin to cable ring. I'm 99% sure it will solve your problem.
          MegaDrum module, DIY A2E pads, DIY hall effect 3 zone hi hat, DIY 1, 2 & 3 zone cymbals, DIY kick beater triggers on DIY modded longboard, direct drive pedals, DIY triple driver IEMs, El Cheapo buttkicker. Various VSTs running in a tweaked Linux Mint. kit pics thread

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          • #6
            Thanks Myrk and Ignatus for understanding the problem and some good suggestions.

            I'll try putting a pot on it. Thats pretty easy.

            If that doesn't work I'll try to explore different piezos. I have another exact same drum and its rim response is a little better (although the head response isn't as good). So there's significant variability coming from somewhere.

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            • #7
              Again, sounds physical rather than electrical. I'd check all your foam/EPDM and check that some isn't compressed from wear and tear, as this would cause the reduction in sensitivity and the inconsistency from 1 drum to another despite being identical electronics.

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