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Kevs-the-name
05-02-2016, 12:11 PM
On a ‘standard’ build concert (if there is such thing), I am trying to decide on sound hole size and positioning. What factors should I be taking into account when making these decisions?

Do the same ‘principles’ relate to all sizes?

thank you in advance

sequoia
05-02-2016, 08:35 PM
Yes... It is all relative and scaleable. It is a math thing. However a tenor is not just a scaled up soprano nor is a soprano a scaled down tenor. The proportions change and that gets complex. My advice: Just measure the soundhole on a concert and copy it.

Wildestcat
05-03-2016, 07:38 AM
Hi Kev. The dimensions given on this webpage offer a good start point for "standard" instruments.

http://www.ukuleles.com/Technology/sounds.html

Kevs-the-name
05-03-2016, 08:23 AM
This has helped a bit thanks!
roughly read as
Sop = 1 3/4 - 44.5mm
Concert= 2 1/16 - 52.5mm
Tenor= 2 5/8 - 66.5mm

Does this sound similar to what others are using?

What about distance from neck join? is this influenced by bracing position and end of fretboard?
so many questions!!!

ProfChris
05-03-2016, 09:33 AM
If this is a figure 8 I'd say "somewhere on the upper bout" is fine, structurally, modifying bracing placement to fit. I'd place it where it pleased my eye.

Wildestcat
05-03-2016, 09:55 AM
Hi Kev. When I designed my concert, I started with Rudy's Bluestem uke pdf drawing (many thanks Rudy - much appreciated), modified the curves and overall width to give a flat face for the neck & tail blocks to sit against, and located the soundhole where it fitted with my scale length, proposed fingerboard end and bracing pattern. I double checked it pro-rata against the tenor design you will be familiar with. It works fine, and you can see the end product in the 2x4 challenge thread.
However, I have just looked at my template for the concert build, and the soundhole I used is 29 mm radius, or 58 mm diameter!

Kevs-the-name
05-03-2016, 10:40 AM
Thanks Paul.

I have had another good look through the 2 x 4 forum... some great ideas.

you suggest that the sound hole was located in relation to the scale length and fingerboard end and bracing pattern.
can you explain this in any more detail please?

Kev

Beau Hannam Ukuleles
05-03-2016, 12:11 PM
The smaller the sound hole, the more bass you get, but it all has to be (i mean should be) in proportion to the body.

I would suggest that on your "standard" concert you do "standard" (ie, tried and true) things, like scale length, soundhole and brace positioning.

Pete Howlett
05-03-2016, 01:21 PM
I use/used dimensions published in Martin history...

Michael Smith
05-03-2016, 03:11 PM
I believe you should stick with the martin sizing as others have led you to. Too large a sound hole and the instrument will sound thin. Too small and the instrument will tend to bark unpleasantly when played aggressively. David Hurd has written quite a bit about the mechanics of all this in his book Left Brain Lutherie if you really want to go crazy.

Wildestcat
05-03-2016, 09:38 PM
can you explain this in any more detail please?

Kev

I'll try in pictures!

90839 90837 90838

Titchtheclown
05-04-2016, 02:00 AM
In threads like this someone usually mentions the words Hemholtz resonators. There is a formula that calculates the ideal size of hole for maximising the amount of sound produced by a given enclosed volume of air. Not surprisingly the size is generally about the same as you see on standard ukuleles, guitars and etc. relative to their size. Science and years of experience tend to converge occasionally.

joebok
05-04-2016, 06:50 AM
Here is a good explanation and practical application of using the previously mentioned Helmholtz resonator physics to give an approximation of a sound hole size: http://www.apsimplepsaltery.com/appendices/helmholtz/

sequoia
05-04-2016, 06:55 PM
90856

Exactly! Actually really my eyes glazed over at that point and I have no idea what that means. Anyway, a very good article on sound holes. Helmholtz. The man should be the patron saint of ukes. The poster does a very good job of making a very complex subject understandable by people like me who are not well versed in spherical trigonometry. Good quote below.

Now, I don’t know how accurate any of this all is, but it seems like a good starting point. If you were to start with an instrument with no sound hole, and gradually enlarge it, the sound would get louder and louder. Eventually it would top-out and start getting quieter again. (Imagine a giant 5″ hole in the top of our psaltery!) This is the best way that I know of to find the ideal sound hole size.

Ha! What I do is just copy the sound hole of instruments that sound good. On a tenor this seems to be 2.5 inches.

Vespa Bob
05-05-2016, 05:17 AM
Quote: "Now, I don’t know how accurate any of this all is, but it seems like a good starting point. If you were to start with an instrument with no sound hole, and gradually enlarge it, the sound would get louder and louder. Eventually it would top-out and start getting quieter again. (Imagine a giant 5″ hole in the top of our psaltery!) This is the best way that I know of to find the ideal sound hole size."

This is all fine and dandy, but how do you make the hole smaller when you've gone too far?:)

Bob

ProfChris
05-05-2016, 07:35 AM
Quote:This is all fine and dandy, but how do you make the hole smaller when you've gone too far?:)

Bob

Bind the inside rim of the hole!

Timbuck
05-05-2016, 10:52 PM
When I was into building Loudspeaker cabs I came across Helmholtz,It was a bit too much for me to understand so just copied well known designs..I came across cabs with all sorts of ports and baffles, ports of differng diameters were mainly with tubes fitted at differing lengths to tune the bass end, and baffles in side to act like horns to increase and project the volume..I have never heard of a ukulele with baffles but you never know.
Here is a ridiculous example of the folded horn concept :)
http://i219.photobucket.com/albums/cc143/shiregreenbod/folded%20horn_zpskekcv6f8.jpg (http://s219.photobucket.com/user/shiregreenbod/media/folded%20horn_zpskekcv6f8.jpg.html)