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Step 4Tuning the Overtones
An Instructables community member (thank you luvtheteddie) had a few questions on how to tune the overtones. My advice seemed to help so I'm adding that information here.
OK... To tune the overtones you will need one of two things,
A. Strobe Tuner
B. Audio Spectrum Analyzer
I suggest the Strobe Tuner especially if you are a musician. Personally I consider Peterson Strobe Tuners to be the best and they also make a Strobe Tuner app for the Iphone/Itouch. I only included the Spectrum Analyzer to give you an alternative.
Yes you can tune the fundamental frequencies and the overtones of all bars just by shaping the undercut of the bar.
Before we get into how to shape the curve, let's review the proper ratios between the overtones. For Marimba and Vibraphone builders it is 1:4:9.88. For Xylophone builders it is 1:3:6.
Now, to tune the overtones you should follow the template in the pictures below.
To tune the Fundamental frequency (1), sand in the center.
To tune the second overtone (4), sand just outside the center
To tune the third (9.88), sand close to the ends of the arc.
Now here is where it gets tricky...Changing one overtone, will change the frequencies of the other two!
For this reason, you have to first get the ratios between frequencies correct, and then sand evenly across the curve until you arrive at the fundamental (hopefully with the ratios intact.)
If you mess up and tune something too low, you cannot (to my knowledge) fix the problem without reducing the length of the bar.
Additionally, you will notice the overtones become increasingly more difficult to tune as you begin to work with higher and higher notes. This is because the sample size/duration/sustain of the higher notes become shorter and shorter. This also makes the overtones more difficult to hear. So do you want to tune the overtones of the upper register? I don't know. You'll just have to play it by ear. (I'm sorry... couldn't resist a bad pun)
Optional:
I highly recommend you read this research article:
Nonuniform Beams with Harmonically Related Overtones for use in Percussion Instruments
by Felipe Orduna-Bustamante
published in the Journal of the Acoustical Society of America
December 1991
OK... To tune the overtones you will need one of two things,
A. Strobe Tuner
B. Audio Spectrum Analyzer
I suggest the Strobe Tuner especially if you are a musician. Personally I consider Peterson Strobe Tuners to be the best and they also make a Strobe Tuner app for the Iphone/Itouch. I only included the Spectrum Analyzer to give you an alternative.
Yes you can tune the fundamental frequencies and the overtones of all bars just by shaping the undercut of the bar.
Before we get into how to shape the curve, let's review the proper ratios between the overtones. For Marimba and Vibraphone builders it is 1:4:9.88. For Xylophone builders it is 1:3:6.
Now, to tune the overtones you should follow the template in the pictures below.
To tune the Fundamental frequency (1), sand in the center.
To tune the second overtone (4), sand just outside the center
To tune the third (9.88), sand close to the ends of the arc.
Now here is where it gets tricky...Changing one overtone, will change the frequencies of the other two!
For this reason, you have to first get the ratios between frequencies correct, and then sand evenly across the curve until you arrive at the fundamental (hopefully with the ratios intact.)
If you mess up and tune something too low, you cannot (to my knowledge) fix the problem without reducing the length of the bar.
Additionally, you will notice the overtones become increasingly more difficult to tune as you begin to work with higher and higher notes. This is because the sample size/duration/sustain of the higher notes become shorter and shorter. This also makes the overtones more difficult to hear. So do you want to tune the overtones of the upper register? I don't know. You'll just have to play it by ear. (I'm sorry... couldn't resist a bad pun)
Optional:
I highly recommend you read this research article:
Nonuniform Beams with Harmonically Related Overtones for use in Percussion Instruments
by Felipe Orduna-Bustamante
published in the Journal of the Acoustical Society of America
December 1991
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