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The Effect Of Carved Depth On Acoustic Archtop


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Everywhere you read that you should have a 1" blank to carve your archtop top out of. However, I was wondering, what is the effect of carve depth on sound, I can't find anywhere that addresses that, they all just go with a 7/8" carve (1"-1/8" at the sides). So anyone with knowledge of how say using a 3/4" blank (and thus a 5/8" carve), or a 1.25" black (and thus a 9/8" carve) would affect the sound of an archtop.

Chris

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How steep the arch is will effect the output or efficiency. A flat surface is easier to make vibrate, but flat surfaces do not have the added strength of the arch(this is the main function of adding an arched surface, or radius to an acoustic guitar). I believe you could play with the arch, but you would have to compensate with modified bracing techniques(vs traditional). If you can get a 1-3/8" piece of wood you can cut it into wedges 1" to 1/4" for a wedge set. It is a pretty efficient way to make sets.

Peace,Rich

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If you can get a 1-3/8" piece of wood you can cut it into wedges 1" to 1/4" for a wedge set. It is a pretty efficient way to make sets.

Peace,Rich

Hi Rich,

Is there a way to do this that would give bookmatched halves? I'm trying to work it out, but I can't see how it can be done. Or is soundboard wood uniform enough that this isn't an issue?

Thanks,

Brian.

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What Benedetto shows in his video is his board was only 16" across... so he cut two 1/2" pieces from the board up where the smaller bout is, and glued them down onto where the lower bout is to add the extra 1" needed for 17". You couldn't even see it later... so with non-figured woods, like straight up straight grained sitka, etc. I doubt it'd be any issue. Now what that has to do with bookmatching.... if you can do that... you can surely join wedges like Rich is saying with each other non-issue.

Chris

PS: Steve Grimes (big Archtop builder) does a 5/8" carve instead of a 7/8" carve :D I found out

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Now what that has to do with bookmatching.... if you can do that... you can surely join wedges like Rich is saying with each other non-issue.

Yes, but if you're cutting wedges - you're cutting at an angle, so the thick parts of the wedge are taken from opposite sides of the board to each other - the grain wouldn't match. That's the problem.

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what is the effect of carve depth on sound

Deeper carve gives more physical volume which results in a guitar with a deeper, louder voice. Sound waves bouncing off a curved surface are directed to one general area, ie. the center of the guitar. Picture a satellite dish catching a signal and bouncing it back to a central point, same thing.

A carved top should also have a matching carved back to ensure that sound waves bouncing back and forth inside the guitar are balanced and not being lost around the edges. If the sound waves are focussed this way you should get a more pronounced, clearer tone out of the instrument. Have you ever played a lute? :D Thats the perfect example for this scenario. Lutes are built with a very round back shaped like a bowl. When the string is plucked the sound waves hit the back and are reflected back in concentrated form to the soundboard rather than being spread out like a flat backed instrument. The lute's tonal voice is one of the purest I've ever heard from any acoustic instrument.

So the deeper carve allows for more contour in the profile, this gives more angle of relection to focus soundwaves to the central area of the guitar. A shallow profile spreads sound waves out more. Which sounds better? depends on what you like to hear. :D

Edited by Southpa
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"Hi Rich,

Is there a way to do this that would give bookmatched halves? I'm trying to work it out, but I can't see how it can be done. Or is soundboard wood uniform enough that this isn't an issue?

Thanks,

Brian."

Brian, you are correct you will not get a bookmatch. I did not say it would bookmatch, but it will produce a set you can use for plates. If you are thinking in terms of the figured wood and getting a spot on bookmatch you have to use a thicker piece(that is why figured carved top sets are 3/4"+ generally. If you are talking about a functional plate or even soundboard(spruce or what have ya) it is not ahuge deal. Actually (as was pointed out to me a while back) the use of totally different woods on each side of a soundboard is a practice used to optimise the function of a board(if you are of the bass/treble side school of thought).

So no bargain way get the killer bookmatched set, but for functional plate sets it is a lot more efficient.

Peace,Rich

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Thanks for the reply, Rich. I guess from what you've written and what Chris has written above that with unfigured soundboard woods the grain is even enough that bookmatching isn't important. That's good news.

Regards,

Brian.

Actually, I mentioned that even totally different woods are even used(different species,different trees). Grain matching or maybe mirroring is a better term. Is not going to make any major structural improvements. The bookmatch is mainly a look, and I do like the look with figured woods.

Peace,Rich

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