On Designing and Building a set of Marimba Bars

----- Original Message -----
From: "barry anderson"
To: jim@percussionclinic.com
Sent: Tuesday, February 19, 2002 1:52 PM
Subject: re bass Marimba key lengths

I'm trying to build a bass marimba using Jon Madin's book. Unfortunately the woods available in NZ are quite different in density and elasticity (and I'd like to use recycled native hardwood for the bars). Is there any formulas for calculating bar lengths based on density, or modulus of elasticity or something? What's the process when you design one? I realize that these questions are (or could be) rather involved, so alternately any direction to a book or whatever would be greatly appreciated as I'm creating a lot of firewood and grey hairs at present. Thanks in advance for any help, as I don't think there are any other marimba makers in my part of the world.
regards, Barry Anderson

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There is good news and bad news for you, when it comes to using alternative timber for marimba bars.

Bad news one - The only two timbers that are both hard enough to handle the beating and really good sounding are Honduras rosewood, and African Padoak. Any timber will produce some sound, but it will all be of varying qualities. I have heard some marimbas made from all sorts of alternative wood, and some of them are pretty good though. The trick is to find a variety that vibrates longitudinally well - that is along the length of the grain. The marimba makers in central America climb into the mountains, and go around tapping trees to hear what they sound like. Some of our Australian Native hardwoods one would think might work well, but when you hit the wood, it sounds as dead as a dodo. Even cheap pinus sounds better, but tends to be too soft for a useful bar.

Bad news two - There is no fixed formula for bar length I'm afraid. Every timber has different properties, and even one tree might be different from another, or wood from one particular part of the tree different. The essential thing to remember, is that we are working with a medium where every piece is unique - changing grain, variations in density etc - its all part of natural tree growth.

GOOD NEWS!
You don't need to worry too much about the length of your bars. Make the top bar first. Cut a short bar that looks about right and see what its fundamental tone is. If you are using a hardish timber it will probably be a little too high, in which case you will need to lower the pitch by removing some timber from the arch of the bar. Then figure out what note you would like to be your bottom note. Cut a bar that has appropriate physical parameters - ie practical looking length and obviously it will be wider than the higher bars. Check the note it produces, then keep removing timber from the arch until you get down to the note you need. You will probably find that these low bars are much thinner under the arch than the upper notes. If you have to remove so much timber from the arch that the bar is too thin - (easily broken with normal playing) then you will need to consider using a longer bar. You will find that there is quite a bit of variation in styles of bar made by even the commercial marimba makers. - for example Musser have always tended to make instruments with shorter bars at the low end, which makes them easier to play on quickly and gives the bar a quick response. Yamaha on the other hand have developed a marimba with low bars that are not so thin. They did this for Keiko Abe who plays with plenty of power and tended to crack the bars. The down side is that the bars are longer which makes them less responsive (because they are thicker) and the instrument a little unwieldy.

Hope some of this has been helpful.

Jim McCarthy

For more help on marimba building you can email Jim.

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