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| sizes of multiple soundholes etc..... http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=13695 |
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| Author: | martinedwards [ Wed Sep 19, 2007 4:05 am ] |
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Hi folks, I'm talking through an experimental commission. The client is as open to "interesting" outcomes as I am, but he's asking about multiple soundholes........ now, PLEASE correct me where (not if  ) i'm wrong,
but bigger soundhole means less bass right? so if that's right, am I right to assume that two small soundholes will sound similar to one large soundhole of the same area? or am I barking up the wrong tree entirely? 
thanks!! |
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| Author: | Alan Carruth [ Wed Sep 19, 2007 5:53 am ] |
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You're right, as far as you go. There's MUCH more that can be said, though. A good start would be William Allen's article on air resonances that came out in American Lutherie #1, and is in the first 'Big Red Book'. He gives some nice general rules about how soundhole size and location can effect the pitch of the 'main air' resonance. If you're thinking of adding a 'port' someplace along with the regular soundhole, keep in mind that the further from the 'main' hole it is, and the bigger it is, the more it will tend to raise the 'main air' pitch. I think it's a good idea in any sort of experiment like that to leave a wide margin around the main soundhole, and make it small. That way you can enlarge it if you want. |
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| Author: | martinedwards [ Sun Sep 30, 2007 7:08 am ] |
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OK, what I'm thinking of now is 4 holes arranged in a square tilted through 45 degrees (ok, a diamond!!)where a normal soundhole would go. as a technical drawing teacher I know that the area of a single circle touching all 4 sides in a square will be equal to the area of 4 circles inside the same square so long as all 4 circles touch the edges and two other circles....... or to put it simple, 4 50mm diameter holes = 1 100mm diameter hole. if this works out it may become a signature feature.......
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| Author: | Ricardo [ Sun Sep 30, 2007 11:56 am ] |
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If you are thinking of two soundholes a la Grimes, his holes are 2 3/4". The additional hole area is somewhat offset by having a larger uninterrupted soundboard which tends to produce good lows. I've heard his guitars and was amazed at how nice they sound. Even with a smaller body, they sound very loud. 
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| Author: | martinedwards [ Mon Oct 01, 2007 2:57 am ] |
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OK, plunge taken....... prototype time on a Stewmac AA top, so not a big financial loss if I need to replace it with something sensible!! here's the drawing, with the rosettes overlapping, each one dipping below that of the soundhole next door....... 
And a run with walnut & maple rings.......... 
the neck end one is into the Transverse brace area so I'll have to improv round that when I flip it over and start bracing!! |
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| Author: | Alexandru Marian [ Mon Oct 01, 2007 3:10 am ] |
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It looks interesting ! But I guess you are losing some active top surface, and some frets ? What about a 12 frets neck? This way you can push back the bracing. |
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| Author: | martinedwards [ Mon Oct 01, 2007 5:14 am ] |
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on a 12 I'll never be anywhere near there anyway, so a missing 20th fret will be the least of my worries!! I'm thinking that the bracing will be like this. Rather than AXE or AXX it'll probably be XXX!! SHOULD give planty of strength to resist all that force in a 12 
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| Author: | Alan Carruth [ Mon Oct 01, 2007 9:10 am ] |
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The area is certainly equal, but the ratio of area/edge is not. Your four small holes have a lot more edge, and thus more drag for air flow through them, than one big one. This will tend to cut down the amplitude of the 'main air' resonance a bit, and will have nearly the same effect on the tone that making the body deeper would. An extreme example of this sort of thing would be the wood or parchment roses that they used in lutes and early guitars, which can cut the 'air' mode peak in the spectrum almost to nothing. This has quite an effect on the lowest notes. Another thing that might come into play is that the four small holes are spread out. I know that a long, narrow slot will have an effective area for the calculation of the Helmholtz resonance to that of a round hole 1/3 the diameter of the length of the slot. That is, a 6" long by 1/4" wide slot acts like a 2" diameter hole, even though it has only about 1/2 the area. Not having any experience with holes disposed as you are proposing (don'tcha love alliteration?) I can't say what the effect will be of spreading them out. I'd suggest making the holes a little smaller to begin with, and having some way to enlarge them later, just in case. |
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| Author: | martinedwards [ Wed Oct 03, 2007 3:29 am ] |
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good call, noted, and taken on board, thanks!! |
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