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Vintageukes
01-02-2017, 04:16 PM
Hello,
Thought I would ask the luthiers as you would know best. In general, what is the impact on the tone of a ukulele with a small sound hole? I know a lot of factors contribute to the tone but I have a vintage taro patch with a pretty small sound hole and although the body is relatively big and holds a lot of air volume and the sound is somewhat thin and I began to wonder if that small sound hole has an impact.

Thanks for any thoughts?

Michael Smith
01-02-2017, 06:05 PM
How small is the soundhole> I find too large a sound whole for a given volume leads to a "thin" sounding instrument. When the sound hole is too small the instrument can tend to bark on some notes. In short my experience is the opposite of what you are asking is true as long as the soundhole is within limits. As an example those thin travel Kalas that the ladies seem to like. They have no volume in the box and sound what I consider thin.

Vintageukes
01-02-2017, 06:31 PM
Thank you Michael, I really appreciate your taking the time to share your thoughts. I just measured and the sound hole is about 1 3/4 which is similar to many of my vintage sopranos but the body is concert size.

This is a ukulele which I know has not been played for more than 60 years before I got it. I can experiment with different strings as well to see what that does. Again, thank you.

kohanmike
01-02-2017, 07:09 PM
This is very interesting to me. A couple of members of my uke group have Kala thin bodies and I'm amazed at how much projection and sustain they have. I also have a tenor uke with two smaller sound holes that has very good projection and sustain. What I'm most interested in is how a new tenor uke I just ordered will sound because it does not have a top sound hole at all, it has small sound holes on the sides all the way around, plus a larger one in the cutaway.

http://www.kohanmike.com/uploads/Uku uke 2 sideways.jpg

http://www.kohanmike.com/uploads/BWA spalted progress 900.jpg

Vintageukes
01-03-2017, 09:27 AM
Interesting design Mike...I've never seen anything like it.

Any other thoughts out there about the impact on tone of having a small sound hole opening?

ProfChris
01-04-2017, 12:45 AM
In theory a larger sound hole favours the treble frequencies, while a smaller one favours the bass. But a uke doesn't have much bass to begin with, so it might be better to say that a smaller sound hole de-emphasises the treble.

If your strings are 60 years old, they probably don't produce much in the way of treble frequencies :)

My first thought would be to try strings which you think will sound quite bright. Fluorocarbons maybe?

But it might be that the instrument needs some playing time to wake it up - although there's no science to suggest it should, many players perceive that a neglected instrument sounds dull until it has been played regularly.

Michael N.
01-04-2017, 01:36 AM
Try covering half the soundhole. Just use a thick veneer and get someone to hold it in place whilst you pluck one string. You could probably hold it in place if you have the instrument facing yourself. Just play one note 'open', one note 'semi closed'. See if you can hear the difference. It's not completely scientific because of course you may inadvertently be favouring one of the two states whilst plucking. I think I tried it many years ago but I simply cannot remember what my conclusion was. I think the effect was much smaller than I was anticipating.

sequoia
01-04-2017, 06:43 PM
This soundhole question comes up so much it puzzles that no one has expressed it mathematically. The soundhole just relieves pressure in the box and allows the top to vibrate. There should be a straight ratio of top area to soundhole area that would be ideal and yet nobody ever knows the answer to this basic physics question. To me this seems a straight engineering solution. I'm not an engineer so I don't know. I make my soundholes for a tenor the same as everybody else mostly does as in 2.5 inches. Why? I dunno. I suspect this dimension is based more in looks than anything scientific. Hey it just looks right. Instinctively though I do understand that the bigger the soundhole is, the smaller the soundboard area is and that is not a good thing. Sometimes I really wish there was a real instrument designer on this forum. Where are you Lloyd Loar when we need you?

Vintageukes
01-04-2017, 08:19 PM
I really appreciate the replies.

Dibblet
01-05-2017, 12:10 AM
This soundhole question comes up so much it puzzles that no one has expressed it mathematically. The soundhole just relieves pressure in the box and allows the top to vibrate. There should be a straight ratio of top area to soundhole area that would be ideal and yet nobody ever knows the answer to this basic physics question. To me this seems a straight engineering solution. I'm not an engineer so I don't know. I make my soundholes for a tenor the same as everybody else mostly does as in 2.5 inches. Why? I dunno. I suspect this dimension is based more in looks than anything scientific. Hey it just looks right. Instinctively though I do understand that the bigger the soundhole is, the smaller the soundboard area is and that is not a good thing. Sometimes I really wish there was a real instrument designer on this forum. Where are you Lloyd Loar when we need you?

It doesn't "relieve pressure". It sets the frequency and Q of the Helmholtz resonance.

There's no shortage of information or maths. Just google Helmholtz guitar.

ProfChris
01-05-2017, 12:12 AM
This soundhole question comes up so much it puzzles that no one has expressed it mathematically. The soundhole just relieves pressure in the box and allows the top to vibrate. There should be a straight ratio of top area to soundhole area that would be ideal and yet nobody ever knows the answer to this basic physics question. To me this seems a straight engineering solution. I'm not an engineer so I don't know. I make my soundholes for a tenor the same as everybody else mostly does as in 2.5 inches. Why? I dunno. I suspect this dimension is based more in looks than anything scientific. Hey it just looks right. Instinctively though I do understand that the bigger the soundhole is, the smaller the soundboard area is and that is not a good thing. Sometimes I really wish there was a real instrument designer on this forum. Where are you Lloyd Loar when we need you?

Work has been done on the physics, though my maths is too basic to follow it easily. My (grossly simplified) understanding is that the air in the body has a resonance based on its volume and dimensions - its Helmholtz resonance. If you hum into the sound hole you can hear that one note resonates more strongly than the others, usually around C or D on a uke. The size of the sound hole can change that resonance - lower if smaller hole, higher if larger. There is a mathematical formula for calculating the volume/soundhole ratio for a rectilinear box, not sure how much it needs to be tweaked for different shaping.

Look for posts by Trevor Gore or Alan Carruth on the Official Luthiers Forum or the MIMF, and I believe the maths and physics is fully worked through in the Gore/Gilet books on guitar building.

For builders like me who prefer a "feel" approach to construction, it's enough to know that the standard sizes for different body sizes are close to the ideal, so that if you change your body size then you have some idea how to change the sound hole.

BTW, all the openings count (sound ports, double holes, etc), and the relevant measurement is the total area of the openings. However, placement also matters, though to a lesser extent than area.

Dan Gleibitz
01-05-2017, 12:49 AM
This soundhole question comes up so much it puzzles that no one has expressed it mathematically.

Some say that:
p = ((3 * V/(4 * π))^(1/3))/2

Where:
V = internal volume
p = diameter of soundhole for maximum loudness

:p

Michael N.
01-05-2017, 02:13 AM
My guess (and it is a guess) is that there probably isn't one 'ideal' but that there might be a range that most people find acceptable. If things were so simple that we could define what an ideal tone is then we would have something to shoot at. But there is no such thing, which is why people buy instruments that sound radically different to each other. I know that I tend to favour bright sounding instruments but my ego doesn't extend to the point that I think that everyone else should favour bright sounding instruments too. We DO know that as we age we lose our upper frequency hearing. Perhaps that is why I tend to like that type of tonality. It's just a theory. I do know that we are faced with a moving target and it's practically impossible to please everyone. You might be hard pressed to please 50% of players. In fact if you were to achieve that you might be doing extremely well.
Of course there probably might be some trade off too. It's not uncommon to 'improve' one aspect whilst another aspect deteriorates a little. You then pick your poison. One thing that I do know. Our understanding of the effects of all these parameters has never been greater, greater than Loyd Loar ever knew. We have at our disposal the entire history and experience of making instruments plus the research into acoustics and all the experiments that have been conducted. There might be a long way to go but we certainly have a much greater advantage than someone working in say 1900.

Rrgramps
01-05-2017, 06:38 AM
David Hurd has some technical data for sound holes vs volume. He has a few spreadsheets that you can extrapolate the data from, containing Helmholtz Resonator Theory calculations as well. Data results are the same as stated by posts previous to mine; small hole tunes for low frequencies, large hole for highs -- provided all parameters are held the same.
http://www.ukuleles.com/Technology/sprdshts.html

There is a multitude of interesting information on other areas in that site too, which can be found on the sitemap.
http://www.ukuleles.com/HouseKeeping/sitemap.html

I really do like to hear the sound coming from the sound hole on the top rim of my only ukulele made that way, which is combined with a sound hole in the soundboard for the audience or band members to hear. Music just pours out, and makes a choir-like effect, or multidimensional hearing experience, for lack of a better explanation. It sounds muted when the top hole is covered.

Technically, both holes could be calculated for throat diameter/thickness combination via Helmholtz resonator frequency to compensate for two holes. Or wing it. LOL You probably wouldn't want to hack an ancient antique though.

sequoia
01-05-2017, 06:26 PM
Maybe one reason this question has never been really nailed down is that it gets just crazy complicated. Also like Michael points out; there is no perfect "sound"... After all these thoughts and discussions I always just throw up my hands and say, "You figure it out and I'll just copy the result". It is beyond me. Too many variables and a lot of them involve calculus because of the curves on the box. I do think I discovered a rule of thumb though: the diameter of the soundhole is inversely proportional to the depth of the sides. Totally primitive I agree, but there might be something to it. 2.5 inch sides = 2.5 inch sound hole. Gotta agree it is symmetrical and easy to remember.

Ken Franklin
01-06-2017, 06:17 AM
I think I remember reading a post on the OLF by Al Carruth where he concluded after much testing that the size of the sound hole had to change a lot before you could hear any difference. In my own building I have noticed very unscientifically that a smaller sound hole has increased the Helmholtz resonance to the detriment of an even response across the fingerboard. So I generally make larger than normal sound holes. There are better ways to increase a more even bass response.