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Rails and cones Whether you’re building a trigger from scratch or doing a home repair, digitalDrummer can help. Philippe Decuyper will find the answers to your DIY dilemmas. Just email your questions to editor@digitaldrummermag.com. This month, we have two questions. The first is anonymous: “I’ve built a cone and rail dual-zone snare trigger and I keep getting slight rim triggering from the head. Is this something to do with the fact that the rail is attached to the lug screws?” USING LUG SCREWS is probably the most practical and least destructive way to attach something inside a drum shell. It is easy to do and this should be robust enough to last for some time. The design can, however, lead to false triggering and it is important to check: Are the two piezo transducers isolated from each other? Is the head isolated from the rim? Are these not the same issue, you might ask. Well, yes - and no… All things that are attached by screws are physically linked. If your rail is directly attached to your shell via screws, both rail and shell will receive vibrations generated by a hit on the rim. It’s fine for rim triggering even if your rim piezo is attached to the rail. The problem here is that your head piezo is attached to this same rail and must be isolated from it. There are various solutions. The cleanest one is to use silencing blocks to attach the head piezo plate to the rail. I personally opted for an ugly but ultra-efficient 4cm-thick kickboard-type foam piece between them (shown here). This is just a first step, though. You can also improve isolation between rail and shell by adding four thick rubber washers. 52
Your lug screws should not be “linked hard” to your rail (and the rubber provides some isolation between the metal parts). In this approach, your rim piezo cannot be attached to the rail anymore as it will now be isolated from rim vibrations. Instead, it must be attached to the shell itself. I use some homemade double-sided foam tape to do it (this is important for many reasons). Now, we have the head piezo isolated from the rail and the rail isolated from the shell – a bit like the double isolation of windows in cold countries. But isolation cannot be perfect (as with windows in old houses – heating is still needed in cold countries). It should, however, be enough to avoid most false triggering issues. Now, what about isolating head from rim? Hitting the head will also transmit vibrations to the shell and then to the rim piezo which is attached to it. You cannot really avoid this, but these vibrations are weak compared to those transmitted by the rim/screw/lug/screw metal chain! To fix any remaining issue, you can adjust the rim sensitivity from your module. Remember that the more your head piezo is isolated from the shell and the more your rim piezo is isolated from the head, the less false triggering will occur. Finally, and slightly off-topic, but nonetheless important: Do not directly attach your head piezo to its plate www.digitaldrummermag.com