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 Post subject: Sound Holes
PostPosted: Mon Apr 23, 2018 4:10 pm 
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First name: Joe
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I'm just wondering what the current thinking is on sound hole size in regard to body size and shape? Does a bigger soundhole produce more volume or less? How big is too big?

Thanks in advance

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 Post subject: Re: Sound Holes
PostPosted: Mon Apr 23, 2018 5:09 pm 
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The size of the sound hole primarily affects the "main air" resonance. Increasing the size of the hole raises the pitch of the main air resonance, and also increases the amplitude. 4" diameter is average for dreds, smaller bodies also have smaller sound holes.

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These users thanked the author Rodger Knox for the post: Joe Beaver (Tue Apr 24, 2018 3:16 pm)
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 Post subject: Re: Sound Holes
PostPosted: Tue Apr 24, 2018 9:25 am 
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Brazilian Rosewood
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The location of the hole also affects the 'air' pitch; the closer it is to the edge the lower the pitch for a given size. There are probably also effects in the high frequency range, related to the 'upper cutoff frequency' of the hole. That my be just as important, but it's harder to document.

The bottom line is that if you want a 'normal' sound stay with the 'normal' size hole for that box size and guitar type. A larger hole will tend to sound more 'treble' and 'forward' in a given place.

A really good article that helps to generalize all of this was the one by William Allen in American Lutherie #1, now available in the first 'Big Red Book' from the GAL.



These users thanked the author Alan Carruth for the post: Joe Beaver (Tue Apr 24, 2018 3:16 pm)
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 Post subject: Re: Sound Holes
PostPosted: Tue Apr 24, 2018 12:42 pm 
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I did an Dred with a 4 1/4" soundhole as an experiment. Called it Big Mouth. I did it cause I have big hands and thought it might be nice while I was working on it. It sounded like crap. I did some wood magic and reduced the hole to 3 7/8" which vastly improved the sound. Now I just stick to traditional diameters - it's way too much work to have to redo that area.

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These users thanked the author SteveSmith for the post: Joe Beaver (Tue Apr 24, 2018 3:16 pm)
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 Post subject: Re: Sound Holes
PostPosted: Tue Apr 24, 2018 2:37 pm 
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Cocobolo
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Speaking of large sound holes...

https://bourgeoisguitars.net/guitars-sp ... ndhole-om/

Keep in mind I think Dana could make a cardboard box and a metal pole into a great sounding guitar. ;o)

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These users thanked the author RaymundH for the post: Joe Beaver (Tue Apr 24, 2018 3:17 pm)
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 Post subject: Re: Sound Holes
PostPosted: Tue Apr 24, 2018 4:01 pm 
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I have pretty much gone with the norm when it comes to soundhole size. But... about ten years ago I walked into a Guitar Center and picked up a 'Special Addition Martin'. It was a rosewood dred with an anirondike red spruce top. It also had a 1-3/4" nut (which I like) and a large soundhole. I didn't measure it but i would guess about 4 1/8 or even a little larger. It was a cannon, very loud and a great tone. I wasn't really looking to buy so I walked out. A couple days later I went back to buy it but it was gone.

Now that I am redesigning my SJ model I've been thinking about testing a larger soundhole on it. The new design is slightly smaller with an 1/8" less body depth than the previous design.

The information here is very interesting and helpful. I am surprised to see the Bourgeois guitar is so successful with what looks like a large soundhole, while having a smaller body than my SJ. Any guesses as to how big the soundhole actually is?

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