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Thinking way down the road here, the beginnings of a design that might call for a non-traditional soundhole are brewing in my brain. So I have a related question/thought experiment: Say that a soundhole of a certain area has been established as working well for a particular guitar design. Cutting through the top to yield this area can be done in various configurations. So all else equal on the guitar, and given the same soundhole area, I would think that round vs. oval, for example, would make only a subtle difference in tone. Moving the hole to the upper bout (supposing the guitar design allows this without other major design changes) probably a more noticable difference, but probably still not radical. Then there's dividing the area among several holes. I've seen a fair number of two hole designs around. What I'm really wondering is what happens if we go to extremes dividing up the area into smaller holes? It seems there would be a limit in how many tiny holes one could make before the normal body air resonance mechanism breaks down, even if the total area is the same. Is this true? Does many small holes really work just like one big one of the same total area? Even if it is the same physics wise, I wonder what the implications for tone would be? I'm interested in what the limits are.

Though I was never too attracted to the sound, I always liked the pattern of small holes flanking the fretboard on the upper bouts of Ovation/Adamas guitars. This pattern doesn't strike me as too extreme, but again I just don't know. Anyone's thoughts/reflections on this much appreciated

Peace,
Sanaka

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...imagine there were no hypothetical situations...

Sanaka,
Well....I'm a guy that constantly looks for something different. However, my knowledge of soundhole size/shape and placement ...etc. only goes as far as my less than a year of building. I see posts with varied equations on all the elements of sound from a guitar and it's way too complex for me at this point. I did do a triangular shape sound hole on a rebuild and it didn't seem to change the sound. It, of course, had a completely new top too....so maybe I got a beeter top sound and less soundhole projection...Who knows.
I DO KNOW, that I cut a sound hole in the upper bout of my first build after it was done and it seems to have boosted it's overall sound.
There are lots of posts on this so try the archives.
Kent

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Wood Creations by Kent A. Bailey
EXCELLENCE IN SCULPTURE, CARVING, LUTHIER, ARCHITECTURAL MILLWORK AND DESIGN

http://www.kabart.com

A good book on acoustics,although not for those unfamiliar with equivalent circuits,is 'acoustics by Leo L. Beranek'. He touches on bass-reflex enclosures which use multiple holes. There are many instances of many small holes being used to vary resistance and mass of the air moving in and out of a bass-reflex enclosure.It is a complicated subject, but the book is an excellent resource. Beranek was a prof. at the MIT acoustics laboratory.So, to answer your question, it can be done but it is not as simple as taking the required area and substituting many small holes adding up to the same area.You have to take into consideration, the spacing of the holes,the diameter of the holes,and the thickness of the holes.Hope this helps.

I did fish shaped soundports. It sounds awesome. One thing to take into consideration is the bracing. Heres a picture of what I ended up with. I'm thinking of doing some more creature shaped ports. Endless posibilities. Good luck.

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Jason Moe
LaCrosse WI 54601

First: Get the 'Big Red Book Vol.1' from the GAL, and look up the article on air resonance by William Allen. It's required reading.

In a nutshell, though:
The hole size and placement more or less directly sets up the 'Helmholtz' air resonant pitch. This couples with the 'main top' resonance to yield a 'main air' mode at a somwewhat lower pitch than that of the Helmholtz mode. This is the lowest resonance that can radiate sound effectively, and accounts for much of the bass response of the instrument.

The larger the hole the higher the 'Helmholtz' pitch, and the stronger the mode in general. The closer the hole is to the end of the guitar the lower the 'Helmholtz' pitch for a given size. Then you have to start thinking about how it all works with the top and back to make the 'main air' pitch you will actually hear.

It's been a while since I read Baranek, but I do have some experience with 'roses' in soundholes that divide the thing up into a bunch of smaller areas. Think about slapping some sort of grill into the hole. In that case, basically, the pitch of the 'main air' resonance will be established by the diameter of the hole, while the addition of the grill adds drag that cuts down on the amplitude of the resonance. I would imaginge that as the small holes get more dispersed the thing acts less like a hole with a grill in it, and gets more complicated.

A slot, like an F-hole, has the equivelant area to a round hole 1/3 the length of the slot, iirc. Since there is more 'edge' for the amount of area, and edge is where the drag (and losses) come from, the amplitude of the mode tends to be lower that it would have been from the round hole.

The soundhole also 'listens' to internal air resonant modes in the box. Some of these aren't heard well by a normal soundhole, and don't contribute much to the sound. Moving the hole very far from the waist will likely change the population of audible modes, and alter the sound. I talked about these modes some in my paper on 'ports' in American Lutherie a while back, and it's on my web site:
http://www.alcarruthluthier.com/Downloads/sidePorts.pdf

I once made a guitar that had two holes at the outer edges of the upper bout. These 'heard' a 'crosswise sloshing' mode in the upper bout, at about 700 Hz, and tended to 'beam' sound in that range toward the player. The tendancy was to back off a bit on notes that had a lot of that sound in them, to even out the sound to the player, which, of course, made it sound uneven to the folks out front.

As usual, this can get as complicated as you want to make it. The bottom line is that the closer you stick with 'standard' design features, the more 'standard' your sound will be. As you start making changes things get more and more unpredictable. Whether they're 'better' or 'worse' is a matter of opinion.

Wow.

Thank you so much, Professor Carruth and everyone. That is of course plenty to chew on , but also perfectly answers my questions. I love the feeling of getting something nailed down theoretically, but the hard to nail ones are usually much more educational!

So the limits are hard to define, but it is evident that pushing extremes in terms of dividing up soundhole area becomes unpredictable in terms of tonal effects. And even altering shape and placement can cause significant changes. I guess it was kinda naive to hope otherwise

One thing I find very interesting is this "edge drag" versus area interplay. If more edge for a given area reduces amplitude, then a circle is the "loudest" shape because it encloses the most area for its perimeter. This points to an intrinsic functional reason for a round hole, rather than just its archtypal aesthetic perfection. Cool!

Thanks again! This rocks... and I'm jazzed!

Peace,
Sanaka

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...imagine there were no hypothetical situations...

Oh yeah, and I will see if I can find Baranek, invest as soon as I can in some 'Big Red Books', and I'm off to read the side ports article

(Kinda going crazy w/ the smilies, I know....)

Peace,
Sanaka

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...imagine there were no hypothetical situations...

I read the sound port and 'String Theory' articles on your site Alan. Both just great stuff, several conceptual pieces falling more into place for me. Your scientific skills are parsecs beyond mine, but you do a great job of conveying the principles in an understandable way. Thanks!

I hope in my post above when I said:

that it was clear that I meant this soundhole thing was of the very educational variety, not that I now had it nailed!

The main reason I find my mind always squashing and moving the soundhole around is that it seems like the standard soundhole placement would otherwise be prime sound-producing real estate on the guitar's top.

Peace,
Sanaka

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...imagine there were no hypothetical situations...

Sanaka wrote:
"The main reason I find my mind always squashing and moving the soundhole around is that it seems like the standard soundhole placement would otherwise be prime sound-producing real estate on the guitar's top."

So it would seem, and yet I've seen and heard several guitars that had the hole moved to free that area up for 'speaker cone' duty, and they were not impressivly louder. One can think of several possible reasons for that, but the bottom line is that people have been trying it for a long time, and keep going back to the 'standard' setup. The bottom line is that it's easy to get hung up on the niotion that some one aspect of the design is 'most important', but it seems to me that the way the thing works as a whole is really what matters. you can take a small hit in top area if it makes the air resaonances work better (whatever 'better' is).

Thank you again, Alan. It is indeed so easy to allow various notions to preponderate over the big picture. I take your words of wisdom to heart. In my case, the next year or so ought to allow me a lot more shop time for guitar building so I can get out of my head and make real life observations.

Peace,
Sanaka

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...imagine there were no hypothetical situations...

Aloha Sanaka,

Here's a link to the www.abebooks.com used book website for the Beranek book:

http://www.abebooks.com/servlet/BookDetailsPL?bi=1422961479&searchurl=an%3DBeranek%2BLeo%26kn%3Dacoustics%26n%3D200000237%26tn%3DAcoustics%26x%3D0%26y%3D0

Another very useful book is "Fundamentals of Musical Acoustics" by Arthur H. Benade. Again from www.abebooks.com:

http://www.abebooks.com/servlet/BookDetailsPL?bi=1394037909&searchurl=an%3DBenade%2BArthur%26kn%3Dacoustics%26n%3D200000237%26tn%3DFundamentals%2Bof%2BMusical%2BAcoustics%26x%3D57%26y%3D7

Enjoy...

aloha,

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David C. Hurd
http://www.ukuleles.com

Alice laughed: "There's no use trying," she said; "one can't believe impossible things." "I daresay you haven't had much practice," said the Queen. Through the Looking Glass by L. Carroll

"Since my house has burned down, I have a much better view of the moon"

David, that is a great price for the Beranek book. I think it cost me $60 back in the early 80's!

Thanks Kawika! I just bought them both, and your book is next on my list

I also have "The Science of Sound" by Thomas Rossing, which as I'm sure many here know is an introductory college level acoustics text. It is a superb primer and covers a lot about stringed instruments, including photos of Chladni tests on fiddles and guitars, and a look at the 'new violin family' created by Carleen Hutchins, who it seems to me layed an awful lot of the groundwork for the kinds of analytical work happening in luthierie today, starting in the 50's.

Hopefully most here know this, but for those who might not, David, aka Kawika, is a fellow Big Islander, all around straight up and kind person, amazing ukulele builder, and top-drawer scientist who wrote the book: Left-Brain Lutherie: Using Physics and Engineering Concepts for Building Guitar Family Instruments: An Introductory Guide to Their Practical Application. At Kawika's shop I strummed a ukulele that had simply ridiculous sustain, I mean rivaling a good guitar, and a wonderful sweet tone and great playability. It's when my brain first finally grokked the ukulele as a serious instrument, and was one of those memorable 'Wow' moments for me.

Peace,
Sanaka

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...imagine there were no hypothetical situations...