The Thin Ukulele: Final Results

This thread follows up on an earlier thread about how the depth of the sides effects the sound of the ukulele. It was sparked by a luthier (sorry I forget your name) who said that the ukulele needed to slim down and that the deep box depth of the traditional ukulele needed to be re-thought and that it could be much thinner. There was much theorizing about what would happen, but little evidence. So I built a ridiculously thin uke to see what it would sound like.

I figured that to find out what would happen, the experiment should be taken to an extreme so I made an uke with 1 1/4 inch sides. Much thinner than was desirable from an aesthetic, structural or sonic perspective in order to see how it effected the sound which could then be extrapolated to a more reasonable depth hopefully being able to maybe dial in a desired response and sound by varying the height of the sides.

I learned so much from this exercise I can't tell you. Basically it breaks down into two parameters. One, structural considerations and two, acoustic considerations. First the structural considerations:

Decreasing the depth of the box by decreasing the sides brings into some serious structural weaknesses. The whole box wants to to rack and it was immediately obvious how much the sides contribute to the integrity of the overall structure of the instrument and its strength. I'm no engineer, but my carpenter sense immediately sent up red flags that the box was dangerously weakened by making such a thin box.

I did not shore up the sides or reinforce the top since the whole point of the exercise was to build the uke exactly the same as the reference uke. The entire build was as close to building a duplicate as I can do using the same wood throughout and actually using a top out of the same billet. Top thickness was exactly the same as was the bracing as close as I could do it. I kept notes on the thickness of the top and thickness of the braces and replicated them as exact as I could. Same wood, same thickness on the top (exactly 72 by the way). The reference uke is as perfect sounding as I can build. Balanced with neither too much tenor or base. California bay laurel hard wood tops.

Immediate lesson among many I learned was as you decrease the depth of the sides is that you decrease the area that the neck attaches to the body. That neck volute is there for a reason and that the neck to body joint has to be strengthened proportionally as the area of the neck heal decreases. Many other considerations I won't go into, but didn't become apparent until I came across them.

OK. Lets cut to the chase and how did the thing sound. Beau said that the attack would be quicker on the tenor side he thought. I agreed and guess what? That is exactly what happened. The high side was emphasized with increased volume and separation and decreased sustain. In other words, clear trebles with nice seperation. The mids and base suffered however and the balance was drastically tenor. Not unpleasant however and the casual listener liked the sound. Personally I think this is going to make a great electric uke.

Conclusion: If you want to emphasize your high end end and increase volume and separation, decrease the box.

Great work. I have found that clipping 10mm off the standard depth of 75mm on tenor makesn no significant impact. It does however make for a more comfortable to hold instrument...

this bothered the heck out of me, i knew the guy had an english name, and finally found it with a search +mandolin +violin. tom parse was the luthier and very big on 1 7/8" same as the mandolin and violin.
i have to agree with sequoia and pete howlett. there are important practical considerations here needing purchase for the neck joint right up top of the list, then the racking issue which is beyond upsetting. with racking you figure it might as well be a solid body and electrified and then life is back in balance. fine idea except it's not the original quest of an acoustic instrument.
pete's approach is nice minus the three eighth inch. a bit more comfort and not much effect on aesthetics. you never get everything you want so something is pretty good. things are a matter of finding balance.

Thanks for the report! This is the kind of thing I love about internet forums. One person's effort teaches all of us something new

The neck joint and racking problems can definitely be solved without making it a solid body, but actually I agree with Tom Parse that 1 7/8" would be a better depth. Then the structural problems (except needing a different bridge clamping method than usual) would probably go away on their own, and it would probably sound better too.

But it's good to push the extremes first, so you can better judge the middle ground later. Nice work!

I have a thin body Famous FS-0 (Kiwaya budget line) and a Kala thin travel. I don't notice too much difference in sound. Yes maybe a little less Low End. But I like the thin profile/ ease of carrying it

Some final thoughts on the thin uke now that I've been able to play it a little more:

- Helmholtz effect: (Helmholtz resonance is the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle.) Some people give it little effect and some say it has a big effect. I think it has a BIG effect and is what is driving that treble. Again, probably no great surprise here.

- Wolf-tone: Definitely wants to be wolfie right at G or even G#. Not unpleasant, but higher than usual with my ukes where the wolves tend to live down around F.

- The thing is really loud and people seem to like the effect. Very loud ukulele sounding instrument. However to my ear the thing lacks warmth and complexity.

- The thing is a little too thin for my comfort while playing. Slides around a little bit too much.

- Nicely balanced weight wise with the heavy tuners and the pre-amp installed in the tail. A perfect balance right at the neck/body join. Got lucky there.

- Sounds great through an amp which really has nothing to do with the acoustic sound. (L.R. Baggs of Money 5-0 undersaddle peizo). I'm probably not going to be sitting around playing this instrument as my go-to acoustic. Still, maybe I just need to get used to it.

Fun project, but that is the last thin uke I build. Still, it is interesting to me that one could dial in sound by varying the depths of the sides rather than concentrating exclusively on bracing/tops/woods. Beau said there is a "sweet spot" and for sure there is. But one persons sweet spot might be another person's canoe paddle.

Interesting project. Now that you went thin, how about trying a "fat" ukulele?

Ha ha ha. As a data point, would be interesting, but not going there. Got better things to do, but be my guest.

sequoia said:

- Nicely balanced weight wise with the heavy tuners and the pre-amp installed in the tail. A perfect balance right at the neck/body join. Got lucky there.

- Sounds great through an amp which really has nothing to do with the acoustic sound. (L.R. Baggs of Money 5-0 undersaddle peizo). I'm probably not going to be sitting around playing this instrument as my go-to acoustic. Still, maybe I just need to get used to it.

Click to expand...

I seriously doubt that the pickup has anything to do with the balance of your instrument. That would be all you, and how you designed it. The location and weight (or lack of) of the pre makes its almost negligible (the battery is negligible too).

As far as "acoustic" sound, the Baggs' Element is sensitive along the piezo inside the body as well. What does that mean? Technically, the guys at Baggs would know better, and I can't repeat how it was explained to me. But for sure you need to pay close attention to its placement, which is why their wire straps are designed the way they are - to keep them away from touching anything. Prior to the Five.0, and prior to the "special" Ukulele Element, I used to order the Elements in pieces, and soldered them together myself because it was easier than taking it apart to shorten the wires. It was then that I was told to not shorten the piezo, and they resized it for me so I wouldn't have to.

That said, I do agree that amplified is probably one of the best ways to exploit this instrument, if anything, for the lack of feedback from the body. . .

I can't say anything bad about thinlines. Kudo's to MGM for starting the trend, and I'd continue to make them as long as there is a market.

DennisK said:

Thanks for the report! This is the kind of thing I love about internet forums. One person's effort teaches all of us something new

The neck joint and racking problems can definitely be solved without making it a solid body, but actually I agree with Tom Parse that 1 7/8" would be a better depth. Then the structural problems (except needing a different bridge clamping method than usual) would probably go away on their own, and it would probably sound better too.

But it's good to push the extremes first, so you can better judge the middle ground later. Nice work!

Click to expand...

dennis

tom claimed his customers liked the 1 7/8" in blind sound tests and there was no acoustic reason the instrument had to be thicker.
do you have a reason, or some experience, for liking this depth?

For those interested, Shawn has a Luthier Insights series, one of which Tom Parse discusses Thinlines.
http://ukulelefriend.com/resources/ukulele-building/

chuck in ny said:

dennis

tom claimed his customers liked the 1 7/8" in blind sound tests and there was no acoustic reason the instrument had to be thicker.
do you have a reason, or some experience, for liking this depth?

Click to expand...

Mostly intuition based on a 2 1/2" depth Cordoba flamenco guitar, and building various sizes of guitar/uke family instruments (no thinlines yet though). For the moment I disagree with the bit that there's no acoustic reason to go deeper. I'd expect a 1 7/8" deep tenor uke to sound quite a bit different than say 2 1/2". Both good in their own way. But I'll have to build some thin instruments myself to confirm that theory. The main one I want to do is a jumbo steel string guitar... I think it would be interesting to have a huge soundboard area but not much air resonance.

Another thing to consider when varying the box depth is to vary the soundhole area at the same time.

DennisK said:

Another thing to consider when varying the box depth is to vary the soundhole area at the same time.

Click to expand...

Oh lord, yet another variable! But the point is well taken and raises interesting questions. As the box depth thins there is a definite change in timbre for sure. I've proven that to my satisfaction. Volume and attack is increased. All things that people like in an ukulele, but balance in my opinion suffers. By increasing or decreasing the size of the sound hole, some sort of balance might be achieved (bringing in bass/mids) while maintaining volume and attack on the trebles. But which way to go? Larger? Smaller? I don't know. Seems that I remember when thin guitars were coming onto the market in the 80's(?) the sound holes were increased in size. How much of this was simply aesthetic driven (they kinda did look cool) rather than for any acoustic reasons. However, I have an intuitive feeling that decreasing the real-estate on an uke top by making the sound hole bigger should be approached with much caution since there ain't much real-estate there to begin with and making the sound-hole smaller? How would that look? Lame probably.

this is turning out to be a great discussion. i wouldn't have any idea about sound hole either and would need to start with something small that got gradually enlarged as you were making observations about sound.
a lot of what people do is based on intuition and sleeping on things. this is our creative process whether it's instruments or pork bellies. i expect a larger box, say 2.5" for a tenor, to have deeper bass resonance than a thinline. not any great deal, just enough to matter to the player. i think pete's creative process is right on at the 2.5" depth. you don't alter your building methods. the customer expects to see a certain shape and aesthetic and it's substantially there. there would be no potential sales lost on that account. you've given the customer something he/she will love more because it's more comfortable to hold. a cigar box uke would look good at 1 7/8". the dreadnought shape at that depth looks like it needs more side depth to sort of round it out better. it's a function of the curved shape and flat top. maybe it's just what i am used to seeing. ?

Ok, after doing a little research (emphasis on little), I've noticed that the ratio of sound hole diameter to the height of the sides is usually (kinda sorta) a 1:1 ratio. This also holds (sorta) true with guitars. My very common design for a tenor ukulele has a 2 1/2 inch side with a 2 1/2 inch sound hole or a 1:1 ratio. Therefore, if one decreases the sides, one can decrease the diameter of the sound hole. Thus an uke with 2 inch sides would have a 2 inch sound hole. This makes sense because contrary to popular myth, the sound hole doesn't "let the sound get out", but just exists as an aperture that allows the air in the box to equalize with the outside (as I understand it). It is the top that makes the sound and it doesn't come out of "the hole". Less volume of air in the thin uke, less the size of the aperture to equalize it. This might be a good thing because by decreasing the height of the sides and making the sound hole less, there is an increase in the vibrating surface of the uke and that might be a good thing. But how would it look? A 1 7/8" side with a 1 7/8" sound hole??? Maybe we aren't ready for that yet...

sequoia said:

Ok, after doing a little research (emphasis on little), I've noticed that the ratio of sound hole diameter to the height of the sides is usually (kinda sorta) a 1:1 ratio. This also holds (sorta) true with guitars. My very common design for a tenor ukulele has a 2 1/2 inch side with a 2 1/2 inch sound hole or a 1:1 ratio. Therefore, if one decreases the sides, one can decrease the diameter of the sound hole. Thus an uke with 2 inch sides would have a 2 inch sound hole. This makes sense because contrary to popular myth, the sound hole doesn't "let the sound get out", but just exists as an aperture that allows the air in the box to equalize with the outside (as I understand it). It is the top that makes the sound and it doesn't come out of "the hole". Less volume of air in the thin uke, less the size of the aperture to equalize it. This might be a good thing because by decreasing the height of the sides and making the sound hole less, there is an increase in the vibrating surface of the uke and that might be a good thing. But how would it look? A 1 7/8" side with a 1 7/8" sound hole??? Maybe we aren't ready for that yet...

Click to expand...

Interesting observation. I'd never noticed such a linear relation between hole diameter and side depth

I do think a small hole in the normal location looks weird (look up django jazz guitars), but if you put it in the shoulder area, I think it would work. And then you can ditch the lower cross strut and incorporate the usual soundhole area as part of the active vibrating part of the soundboard... which may or may not sound better Perhaps better for concert size, and worse for tenor? At least when using hardwood soundboards, since at the larger size it would probably get too heavy.

This thread has been an insightful read. I've played a few thin-bodied Ukes and never were any lacking in volume if that is a concern one may have. I can just add a player's observation based also on my own Brüko #2 Flatbody (Brüko's name for their thin-bodies). Though this model is a custom that adds their optional arched-back. It is currently strung with Ken Middelton's Living Water strings that I prefer over the stock stings which, to my ears, were thinner sounding than the living waters. Overall, the Brüko thin #2 produces quite a loud and well-projected sound with what I feel couples an increased clarity of the mids and highs with some of the low-end tone removed, but without being overly trebly and certainly not shrill-sounding as one may fear these could be. It's as loud, if not louder than any of my other Soprano Ukes. But factor in also that the brighter tone from this particular model is also being influenced by the all-maple body construction it employs, so it's not exactly a direct comparison to my Brüko #6 with the standard body depth and use of mahogany instead of maple.

The soundhole, bridge and all other instrument measurements (length, etc)/locations are the same as my Brüko #6, and if depth is in fact playing any role in the tone, as I presume it is, then I would feel that an arched back would too have some measurable role in the resulting sound. Regardless of what sound impact the arched back may have, it certainly adds greatly to the aesthetic appeal of the instrument and also adds more comfort while holding it compared to a flat-backed Uke.

Bottom line, I like thin-bodied Ukes and after all of this thread discussion, I am now motivated to possibly add another to join my Brüko #2 one day, but maybe a different scale and with different tone wood.

Here's Pete's video of his Brüko Flatbody demonstrating it's loudness...

sopranos may be their own experience. my interest is how the tone changes with depth in the tenor size and possibly baritone as well. the soprano has a nice presentation with a thin body. this aesthetic doesn't stay constant as the size grows larger.