I did some brief tinkering in the workshop today while Ruby played in the backyard with a friend.
In order to amplify and reinforce the sound coming from each bell (the metal plates that make the noise are called bells, even though they aren’t bell shapes), one puts it over top of a precisely dimensioned box (or tube). A phenomenon known as Helmholtz Resonance takes over and amplifies the specific frequencies you want to hear. You can see these resonators hanging down below large concert xylophones and marimbas.
Anyway, I’d done some quick calculations today to figure out if I was in the ballpark for the dimensions I’d need for my own resonators, and things were close, I figured I’d turn my attention to the part of the celesta that would hold the bells.
Each bell would be attached to a thin plywood “card”. Instead of putting the bells above the resonators, I’d put the bells inside the resonators. The cards would then form the side walls of the resonators and everything would be fantastic, right? Well, I never got to the resonating part.
Turns out that mounting the bells is a very finicky business. You need just the right amount of pressure at just the right contact points or you get dramatically reduced sustain — or no sound at all. Thud.
Complicating matters, my design gives me just 3/8″ in width for the space each bell needs to live in — mounting hardware and all.
So this evening I’ve been playing screws and rubber washers and that kind of stuff. I’m getting closer , but I haven’t found anything yet which sounds as nice as the original rubber supports the xylophone came with. You can see the black rectangle of rubber with the points in the photo on the right; it’s perfect except that it’s already a 1/4″ thick, which doesn’t leave enough room for the bell itself in that little 3/8″ cavity.
So I’ve been hunting around the internet for the part I need. Turns out a “bumper grommet” would be perfect but I don’t think they make them with a small enough point. Self-stick dome-shaped bumpers might work — like the kind you stick onto the bottom of furniture — but I haven’t found any lying around the house (yet).
Like everything else, this is a matter of finding a simple, cheap, repeatable, safe solution. I could hand-carve a slot into the plywood for the stock bell support, but I’m not about to do that 64 times. Something else will work! But what…?
UPDATE (ten minutes later)
I think I’ve got it! Or something. I tried sticking toothpicks into some holes left behind by tiny screws, and … amazingly, I think the sustain is even better than the rubber that the xylophone came with. I suspect that the toothpicks will deteriorate over time, though, but they’re giving me a very good workable solution for the first time so that’s good news. Now I’m thinking maybe some old-fashioned thumbtacks will do the trick…