Planning to Build a Marimba? #3 - (Discussions with Jeremy Daross)
-----Original Message----- From: "Jeremy"> Sent: 22/09/03 5:24:00 AM To: email@example.com Subject: American marimba playing, etc...Jim,
I found your site through a web search for bass marimbas. I hope to make one (eventually), and I wondered what you could tell me about sizing the bars and resonators. Iım thinking of using a wood other than rosewood or padouk, just to be different, so I donıt know if I can assume that the dimensions will have any relation to commercially produced models. Iım sure there is math behind all this, but I donıt know where to look for it. You seem pretty knowledgeable, so Iım hoping you can help me figure out how to design the bars and resonators.
Also, my primary expertise is marching percussion (Iım currently an instructor at SpringFord High School, and Iım a member of the Reading Buccaneers Drum & Bugle Corps), so Iıd be glad to offer an American perspective on the activity when you put that part of the page together. Do you guys have drum corps down there? You can check out our site if you want: www.readingbuccaneers.org.
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Thanks for your email Jeremy - and I will indeed check out your link. I welcome any input. We don't have much at all in the way of drum corps down this way sadly, and that is probably one of the main reasons that section of the website hasn't been developed yet. I have so little time for non-profit things like the website between a hectic teaching and giging schedule, so I usually need a bit of an inspirational nudge. Its also why its taken me a while to reply to you - sorry about that!
As for the marimba:
There is no real maths behind bar dimensions as such - the tuner will carve the bar until the notes are correct. Differences in bar sizes that you may notice from one commercial manufacturer to another is more to do with what they are aiming for with their instrument. For example Yamaha make instruments for Keiko Abe who quite frankly pounds the living sh%$#t out of them. That's OK, because she does it musically, and hey - she's not paying for the replacement bars which incidentally she uses quite a lot of. What that means though, is that Yamaha have tried to make their low ends more durable by making the bars longer down there. This means that they don't have to be carved so thin to be at correct pitch, so are a little stronger. It also makes for a huge leap between "white" and "black" notes unfortunately, and most people feel it doesn't sound as good - their bars don't vibrate as freely. Musser, and to a certain extent Malletech, tend to go to the other extreme a bit with shorter but thin bars which have a tremendous response but you play them strongly at the peril of your bank balance. In general there has been a tendency for all manufacturers to make low end bars wider in recent times as the repertoire demands more low end both in frequency and volume of notes. Best thing for you to do is find a heavyish and fairly hard timber which isn't too crap sounding - you may have to go around tapping planks for a while and make a few experimental bars. Then find a commercial instrument with dimensions and a sound you like to model your bar lengths and widths on. Make a high bar and a low bar as a test to make sure the timber you have chosen is going to work at those dimensions. If the instrument you are building is not of the same range as the commercial one - doesn't matter too much - main thing is to get a feel for your timber and how much it needs to be carved to lower the pitch. If you find your lower bars are getting too thin, you will have to make them longer. Work that out first though, as of course you need an even graduation in length from top to bottom of the instrument otherwise the string holes will not line up.
Once you have your bars the resonators are relatively easy. I still feel you can't go past the ole' PVC pipe for resonators - its cheap, easy to work with, comes in a variety of sizes, and you can buy the end caps ready made as well. You know the approximate length of the pipe for each note - slightly shorter than 1/4 of the note's wavelength in air. Select pipe diameter about the same as the bar width - it will vary along the length of the instrument most likely. Work out how much you need of each diameter and how many caps and elbow joins etc. Cut the pipe to a bit longer than estimated correct length (1/4 wavelength minus end correction) bung the cap on, and test for resonance under the actual bar. You will have a bit of play in the length as the end cap and any joins slide a bit before they come apart, so you can test shorter and longer without cutting to see what's best. Then you can cut the pipe gradually shorter (no cut more than you can compensate for with the sliding of caps and joins!) till you have found the best sounding length of pipe. Mark the positions of the sliding bits with a texta or similar, so when you come to glue them you can slide straight to the correct length before the glue grabs hold - which it does very quickly, so make sure you put joins etc on the right way round to start with!
Once all the pipes have been made, you will probably want to join them all together somehow. Usually some form of steel or allum strip can be riveted to the pipes on both sides. Just lay the pipes out - drill hole through metal and pipe in one go - rivet through should seal it airtight as it makes the join. (make sure you use rivets that seal the hole!) A strip either side at the top, and one on one side on a bit of a diagonal at the bottom is usually enough. Spray paint!
Feel free to ask if you need any more info, and it would be great if you could drop me a note or two as you progress. I'd love to know how you get on.
answers by Jim MCCarthy - 11/09/2003
For more help on instrument building you can email Jim.