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RWD
`Olu`olu
USA
850 Posts |
 Posted - 03/25/2006 : 05:41:34 AM
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Does anyone know of a publication or web site describing the process of scalloping braces to tune a guitar top to another frequency? I was told that it could be lowered a half step to improve the tone of the 6th string in slack key tunings.
Thanks
Bob
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Reid
Ha`aha`a
Andorra
1526 Posts |
Posted - 03/25/2006 : 07:23:13 AM
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Where did you hear that? I have hung out with, and talked a lot with, quite a few good luthiers, and while some of them scallop braces significantly, none of them has ever done that to tune a guitar to another "frequency". They use finger planes after a top has been put on to tune the volume/response of a particular frequency range (mostly by shaving the braces near the bridge plate). But, the frequency (or frequencies) is not changed.
Making the sound hole larger or smaller can change the relative amplitude of a range, too. Smaller holes accentuate bass response.
...Reid
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RWD
`Olu`olu
USA
850 Posts |
Posted - 03/25/2006 : 11:11:32 AM
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| I did mean the response to a lower frequency. I talked (telephone) with a well known luthier from NY. He said it was possible to make a guitar respond better to alternate tunings with low C, by "tuning" the top a half step lower. For all I know he may have hung up slapping his leg and having a good laugh with the his co-workers, but I buy into the concept :) |
Bob |
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Lawrence
Ha`aha`a
USA
1597 Posts |
Posted - 03/25/2006 : 2:11:17 PM
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Reid -
Put your physics hat on. A guitar top behaves like a bendable piston. The outer edges of the top where it attaches to the guitar sides behave like a spring. The already existing scalloping of the braces increase this effect. If you thin the scalloping or the top (or both) near the sides it will reduce the spring constant of this area. This will, in-turn, lower the first self-resonant frequency of the top, causing a greater motion at the lowest frequencies.
Whether you can scape off enough material to lower the "tap tone" a half step remains a question. AND, even if you can, the strength of the top will be reduced and the instrument will be more delicate and the (inevitable) buldging of the top due to string tension will accelerate.
My conclusions from first principles are:
......1) Yes, you can do this and it WILL WORK to some extent.
and..2) You may not want to!!
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Mahope Kākou...
...El Lorenzo de Ondas Sonoras |
Edited by - Lawrence on 03/25/2006 2:16:52 PM |
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RWD
`Olu`olu
USA
850 Posts |
Posted - 03/25/2006 : 3:56:42 PM
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Since reading your first question, I did think more about if a top could be "tuned" or not and decided that it could. Now, after your second response, I agree that it may make the guitar more fragile and I may not go that route. I am especially convinced that I should not attempt to do it. An experinced luthier might be able to change the response without weakening the guitar, but it seems more likely that it would to some degree.
My three classical guitars have excellent tone and volume with the 6th tuned to C (in F Wahine).
Thanks for offering the comments.
Bob |
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Reid
Ha`aha`a
Andorra
1526 Posts |
Posted - 03/26/2006 : 04:32:16 AM
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Lawrence,
What you say is correct for a tap tone (a tap contains a lot of frequencies) or a response to excitation, in general. In actual playing, the *string* produces the frequency. Then the top will respond (resonate) to a greater or lesser extent depending on the parameters you describe. What you said is just another (and more exact way) of saying what I did when I wrote: "tune the volume/response of a particular frequency range (mostly by shaving the braces near the bridge plate)".
We are talking past one another.
...Reid
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RWD
`Olu`olu
USA
850 Posts |
Posted - 03/26/2006 : 12:01:41 PM
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Yeah, I had the same feeling, but it all came out in the end. I understood your expainations and points of view.
Off the subject: A very unususal choice for a member picture...maginifying glasses? I enjoyed it! I am a mechanical designer by the way.
Thanks again
Bob |
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