Replies to This Discussion

Permalink Reply by JL on March 28, 2016 at 1:32am

wheels in the mind are now spinning, long thin slots actually push more air in/out than a circular hole...thanks for posting this, it will definitely factor into my builds

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Permalink Reply by Bluesheart on March 28, 2016 at 9:47am

Good info, thank you.

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Permalink Reply by Nathan Binns on March 28, 2016 at 2:19pm

I'm thinking about f holes (although C holes look nice and effective too) for a ukulele gourd that's in the planning stage. Does anyone have any idea where they should be placed? Violins have them placed in the middle and skinniest part of the body. Something in my gut is telling me to put the holes toward the front of the gourd. That might be influenced by he design of an ovation guitar. However, looking at the older models there, the gourds shape would be similar to the 4th instrument. So maybe they would work best in the back.

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Permalink Reply by Murdoc_420 on March 28, 2016 at 7:16pm

I tried to read the full document but you have to join their site..

 I bet it's simply because the f hole has the same 'volume' for the sound to escape, but it covers a larger area of the instrument.

 All the sound doesn't have to travel to the middle hole, it escapes almost immediately on both sides top to bottom.

 What I find most interesting is the fact of trial and error over human evolution. The fact that nobody is content with the round hole, they kept striving for something better. Would be interesting to talk to the first guy that thought 'a round hole can't be the best solution'.

 Even better is when human evolution and technology have come as far as it has, and yet people can still make great sounding instruments from small boxes.

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Permalink Reply by Ron "Oily" Sprague on March 29, 2016 at 7:04am

Murdoc,

Nope. It's about the "length of the coastline." What I mean is, the increased surface area of the edge of the f hole. It vibrates in a fairly narrow frequency range, all along that edge, as opposed to the vibratory dead spot in the center of the round hole It's not about the sound "escaping." With a round hole, you simply have less vibratory edge than with a c or f hole.

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Permalink Reply by Nathan Binns on March 29, 2016 at 1:19pm

How does position on the soundboard effect this?

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Permalink Reply by Ron "Oily" Sprague on March 29, 2016 at 1:25pm

It definitely does. Look at a violin: the f holes are positioned where the curve of the soundboard starts to drop down to the flattish part, and the bridge is set right between them. For this to work well on a CBG, the bridge should be set a lot closer to the middle of the box, and the top (or bottom) needs to be pretty thin (3/16" or less).

Otherwise, they're mostly decorative.

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Permalink Reply by Nathan Binns on March 29, 2016 at 2:11pm

Ahhh...now that I look at those pics again I do see how the bridge is set in the middle of the holes. That's how I'll position mine too. I'm making the soundboard myself so it will definitely be thin enough. Thanks for the tip.

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Permalink Reply by JL on March 29, 2016 at 11:28pm

with your sound holes that close to the bridge you will probably need bracing under the bridge to keep the cigar box from caving in.  google for images of "violin bass bar"

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Permalink Reply by Kigar on March 29, 2016 at 3:06pm

Maybe the other benefit of a long slot is the top is free-er to move between the slots, it might move more air as well.  If it was just about the length of the perimeter, a long squiggly slot would be better, and who knows, maybe it is.  Or even several narrow parallel slots?  It seems the ends with the ball shape may also help balance the frequencies, but all of this is armchair engineering I admit.  Maybe they just looked cool.

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Permalink Reply by Ron "Oily" Sprague on March 29, 2016 at 10:43pm

Nope, there's frequency engineering involved. Admittedly, it took a couple hundred years of trial and error, but the Cremonese violin masters knew what they were doing. Another thing, if you look at a violin: the top is curved. The edges of the f hole are not in a flat plane; one side is higher than the other. The edges of the f hole vibrate, very similar to the way your vocal cords do.

Several parallel slots is precisely what Godin Guitars does in the left upper bout of their acoustic and acoustic-electric tops. Tonally, they're different than a standard round hole acoustic.

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Permalink Reply by Kigar on March 30, 2016 at 2:18pm

I didn't mean they didn't have engineering involved, I meant my speculation didn't!  Violins make amazing amounts of sound for their size, they must have known what worked and what didn't.

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