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| Difference In Top and Back Tap Tones http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=25644 |
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| Author: | WendyW [ Sat Jan 23, 2010 12:05 pm ] |
| Post subject: | Difference In Top and Back Tap Tones |
I know that a braced top and braced back should have different tap tones in order to avoid wolf notes in the finished guitar. This is pertaining to traditional classical construction in a solera and I have two questions: 1) After determining the tap tone of the top and assembling the top, neck and sides in the solera, I braced the back and carved the braces, only to discover that the tap tone of the back was the same as the top. In this case do you just keep carving away at the back braces until the tap tone changes enough, or do you go back in and change the fan braces? 2) What is the easiest, cheapest, and most reliable way to determine the tap tone. I taped and tapped and then tried to match the tone by plucking the string of another guitar, but there has to be a more acurate way without spending a bundle on some electronic equipment. Thanks, Wendy |
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| Author: | WendyW [ Sat Jan 23, 2010 12:06 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
That was a typo, it should read tapped and tapped, not taped and tapped. There was no recording involved. |
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| Author: | Jody [ Sat Jan 23, 2010 12:55 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
petersons strobo soft is about $100.00 with a tap tone feature that works well. I am just plugging my micv into the jack in front of my pc . your top and back could be the same pitch , or if you are not covering the soundhole , you are probably getting the body cavity resonance , at both places. just my .0005 cents Jody |
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| Author: | WendyW [ Sat Jan 23, 2010 2:16 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
Jody, I'm talking about tap tone of the braced plates before they are glued to the sides and neck. It is just the braced plates, so there is no cavity resonance. And thanks for the suggestion, but I don't have a computer in my shop, just a pc in my office. Wendy |
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| Author: | mhammond [ Sat Jan 23, 2010 3:55 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
Wendy: As you work with the two plates you will sand, and bind, and finish them. Each of these subsequent operations will change the resonant frequencies. I know you would be more comfortable with at least a half step tone difference now, but the plates will change. You could chisel off a back brace or two and install heavier pieces now, that would get you your higher back tap tone. However if you just go ahead I'm 99.9 % certain everything will work out ok anyway. Usually as you thin the perimeter of the top plate the frequency drops and you'll end up alright. My advice; stiff upper lip and carry on---- Mikey |
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| Author: | Jody [ Sat Jan 23, 2010 5:56 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
wendy I think you are in a good spot, when you glue on the bridge , it should drop- the resonance of the top . Jody |
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| Author: | Hesh [ Sat Jan 23, 2010 6:03 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
HI Wendy - I think that Mikey is correct. Ervin Somogyi calls the top the heart of the guitar and the back the lungs of the guitar. If I didn't think that Mikey was correct, but I do, and I insisted on changing something I would slightly reduce the stiffness of the back. My reasoning is that a slightly more flexible back will, if Ervin is correct, increase the lung capacity of the guitar while lowering the fundamental of the free back plate. There are other choices too but again I think that once the plates are no longer free plates the changes that they both will undergo will not yield the same notes. Good question!!!! Nice to see folks voicing at this level!!! |
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| Author: | Alan Carruth [ Sat Jan 23, 2010 7:37 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
The back and top change in different ways and to different degrees when they are glued to the rim. I seldom see modes at the same pitches in the top and back before they are assembled, but they can end up very close once they are. It's the assembled modes that count. If you're just starting to keep track of this stuff, then the best thing you can do is simply that: keep track of it. At this point you have no way of knowing what that guitar might have been if you hadn't made the changes you did. If you are following established plans, or making something in the way you have in the past, and it worked out before, then it's likely enough to work out again. If it does, then you know you won't get into trouble if you see the same values another time. If it doesn't work, at least you'll know what to look at in the future. There are generally reasonable ways to correct a guitar that has not turned out well, but unless you already have a data base of how things worked at different stages that you can refer to, the time to think about those sorts of corrections is when you really know you have a problem. |
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| Author: | WendyW [ Sat Jan 23, 2010 7:40 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
I actually had already scalloped a little more off the back braces to try to change the tone and it changed a little, I was just wondering how other people deal with it. I appreciate the answers. So how do you all measure the tap tone of your plates? Are there really sensitive tuners that will pick it up or are you doing it by ear? Wendy |
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| Author: | David Malicky [ Sat Jan 23, 2010 8:57 pm ] |
| Post subject: | Re: Difference In Top and Back Tap Tones |
I find Audacity pretty easy for finding peak frequencies. You would need a computer mic, preferably a good one, but any will work. Quickstart in this post... viewtopic.php?f=10101&t=24630 |
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