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Sound hole size

Hi all I'm just about to start building a prototype for my cigar box mandolin, and I'm wondering if I need to make a specific sound hole size, or doesn't it matter too much, I am wondering this as I've seen lots of cbm's with loads of different size holes
Thanks
Elliot

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Permalink Reply by Thomas "Duck" Petry on August 4, 2014 at 8:13am

Good point RTS. It ain't rocket surgery. Just a fun thing to experiment with when ya get bored.

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Permalink Reply by Titch the Clown on August 4, 2014 at 9:34am

If you want to work out the science, the soundbox is a hemholz resonator and any good internet search engine will find you a site dedicated to how important that is and what the equations are. The end result - big box big hole small box small hole. So look at the hole size on traditional luthier made instruments for comparison. The shape and location and size of the hole/holes affect how the top vibrates also affecting volume and tone - not to mention the structural integrity of the box.. After having studied this you will probably end up with what was said earlier in the thread but have got a small understanding of the rocket surgery involved.

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Permalink Reply by Thomas "Duck" Petry on August 4, 2014 at 10:01am

You can make it as complicated as you want. It still goes back to what Cigar Box Guitars are. A stick in a box. I'm sure that there is a formula of how many square inches or decimals there of the sound hole should be relative to how many cubic inches of volume there are in the box and some people are really concerned about that. I don't fit in that group of people.

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Permalink Reply by Titch the Clown on August 4, 2014 at 10:53am

And that my friend is the beauty of science. It works just as well on a stick in a box as on a million dollar 16th century violin. And if what works works already then ain't nobody can tell you it ain't scientifical. Just like having more than 3 frets on a ukulele it may just be for showing off even if it is just fancy book learning.

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Permalink Reply by Ron "Oily" Sprague on August 4, 2014 at 12:40pm

There is. I have it in a spreadsheet. ;-) And interestingly enough, for a typical 9 x 7 x 2 box, a soundhole of 1.25 inches is about optimum for typical guitar frequencies.

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Permalink Reply by ReturnToSender on August 5, 2014 at 12:08am

There is a Rocketomitrist in our midst!...but "where" is the optimum location?

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Permalink Reply by robert jones on August 5, 2014 at 12:21am

Start at the neck and work toward the tail, you'll know when you hit the right spot.

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Permalink Reply by Ron "Oily" Sprague on August 5, 2014 at 1:35am

Upper left bout or shoulder for a right hander, emphasizes the bass. Middle of the box for better mids and highs. Or a small number, say 3 different sizes, like an Ovation Elite, in one corner. Or a Soundport in the side of the box facing the player. Or a thin rectangular port beneath the neck, due to an excess of zeal. Or none at all. They all work, and give different tones. Soundboard thickness also comes into play.