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Problems with noisy Marimba Resonators (Qs ALEJANDRO SUAREZ)

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-----Original Message-----
Sent: Wednesday, 28 November 2007 10:55 AM
Subject: marimba build from Spain
Hi Jim,
Iīm Alejandro from Spain.Your site itīs very very interesting. Here in spain it does not exist some people with that to speak of these subjects I build my 4 1/3 own marimba in this summer 2007. I used many information about this and iīm very happy of the results. But I have a problem with the sound. I used a PVC (60x1,8 and 50X1,8) for my pipes. In the high and mid register the sound is really good (G3-C7) but the sound in the low register itīs bad. In this notes I listen a buzz noise in the pipe. I try to separate the pipe from the bars and the it disappears but the quality and volume it decreases. If i put the pipes at 2 cm from the bars = buzz. If y put the the pipes at 7 cm from the bars the buzz it desappears but the sound itīs poor.
Whatīs do you think about this?
When we can buy the "building guide and instructional videos for marimba?"

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Hi Alejandro..
The P3 marimba building guide is due for release in about 2 to 3 weeks. [Now available!] The website is being updated tonight with some sound and video info if you want to have a look.

About your specific problem:
It's very hard to tell without being there to test things out myself, but it DOES sound like your resonator might be a little too short.

Of course it might also simply be that your resonator is just not wide enough to produce the volume you are after, but 60mm should not be too bad. Commercial instruments tend to use slightly bigger diameter pipes on the bottom of a 4 & 1/3 - about 70mm for the A-c then 65mm etc. 60mm is not far off though, and the result should not be that different assuming that the bars are OK. As your middle register bars sound good, there is no reason to think that your low ones would be bad.

When a resonator is placed too close to the bar, 2 things happen.

  1. There is a buzzy sound produced. Actually it's not really a buzz like something vibrating against something else - it's a little different. Almost like a slight "growl". It is caused by the waveform breaking up at the resonator mouth, and it usually takes a split-second for the growl to sound. It happens in the middle part of the note.
  2. The close bar have's the effect of partially closing the resonator mouth, which makes it's resonant pitch go DOWN.

This is why I suspect that your low resonators might be too short. With the bar close, the resonator is lowered and becomes in tune with the bar. It also takes more energy from the bar, so it is louder. These two things make it sound good, but the growl makes it sound bad. If the resonator is lowered away from the bar so the growl disappears, then it will naturally be a bit softer, but it might also in your case be becoming out of tune with the bar. This would cause it to be both less resonant, and also of badly defined pitch. (there is actually two notes competing with each other)

All of this is of course a bit of a guess, because I can't hear it for myself, and I'm not sure what process you are using to tune the resonators.

Best of luck!
Jim McCarthy

Jim Reccomends for comprehensive blueprints and building guides to make your own marimbas.

answers by Jim MCCarthy - 19/03/2005

For more help on instrument building you can email Jim.

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