Why no sustain

I'm trying to understand how the uke top works. The one I just built has an odd quality, in that it has very little sustain. The notes die out very quickly. The decay, what little there is of it, ends in high pitched overtones. I don't think is is too desirable, and annoys me. Wondering what went wrong....did I make the top too thin? Too thick, too stiff, too loose?

And is this even considered a bad thing for a ukulele? It definitely has some volume, vs a guitar or something where some sustain would be preferable. Instinct tells me there should be more sustain, and the decay should have more fundamental. But not too much, as I think the uke should err on the side of volume.... But those high overtones... weird.

Loud but little sustain suggests the top is very thin. Think of the sound you get from a banjo uke - is it somewhat like that?

Tell us what wood you used and how thick the top is.

Top thickness and bracing are related, so a thin top with souter bracing might work better. But as a rule of thumb, if your top is thinner than 1.6mm you're at risk of heading towards a banjo-like sound.

There are no rigid rules though, each piece of wood behaves differently.

I wish I knew the science of it myself. I have my favorite solid mahogany concert scale uke which was made by Bruce Wei. Had it for years, and love the sustain it has. It has more sustain than any uke I have ever played. I think it is mainly the luck of the draw really. It is usually in the case when I am not playing it, but the times I do hang it on the wall, it actually believe it or not hums all by itself. Just by any sounds or voices in the room. When you talk near it, you can actually hear it resonate and hum. Really cool IMHO. It's like it wants to sing all the time. I can't explain it, but do have a theory (right or wrong). It has a plaid pattern carved in the entire top, and I am not sure if that gives it it's sustain due to the carving in it giving it more surface area than if it were all flat, but it's a theory. It also has sort of an exaggerated large lower bout in relation to it's upper bout. Not sure if that has more to do with it too. It's a sexy shape I always thought. But might also have something to do with it. I have had so many people wanting to buy the uke when they hear it. But, it will not ever be for sale.

It's Western Red Cedar. Around .075 thick. Probably closer to .065 towards the edges, and .08 in the middle.

hoji said:

Wondering what went wrong....did I make the top too thin? Too thick, too stiff, too loose?

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All of those things or none of those things. A lot of variables and it can be hard to pin down what went wrong. Not only that, but it can be a combination of variables. I am not a real luthier and the resulting sound is always a little different on each uke. They never sound bad, just some of them sound really, really good and some not as good... As for sustain, awhile back I was using my player uke to tune up a new uke I made and I noticed that when I plucked a string on the new uke my player uke would vibrate to the sympathetic tone and it was three feet away and it would hum for 10+ seconds. I then put the new uke in the same spot and plucked the player uke. Alas, no sympathetic humming. Maybe that is why I keep the player.

"New" wood simply has more internal damping than old wood too - give it some time to dry out, perhaps let it "tan" in the sun for a bit, and see if it opens up.

Some people have gone so far as to bake instruments (including relatively expensive violins with poor tone) to try to age the wood, but I personally think that's a step too far and the risks outweigh the gains.

Leave your ukulele in the sun??? Really???

jhnmdahl said:

perhaps let it "tan" in the sun for a bit

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Sun tanning violins is a common practice, but it always happens before the finish goes on.

Yeah, hopefully the wood opens up over time. For now the problem is somewhat mitigated by a lighter set of stings. Sustain isn't there yet, but the piercing overtones are diminished considerably.

Try adding some mass to the top - a blob or two of poster putty would do. Start by adding it to the bridge, then move it to different spots on the lower bout. If it helps, you can then glue a similar weight inside at that spot.

ProfChris, wow.
Adding 5 - 6 grams of clay to the bridge:
More sustain
Less plunk/punch
Less harsh overtones
Less volume
Less "responsiveness"

Definitely worthy of more experimentation.

RPA, good point - I guessed that if he's still fiddling with tone the ukulele is still unfinished. I suspect you might get similar but lesser effects by sunning a ukulele that has already been finished, but I don't have experience doing so.

Give that one away or burn it ....The next one will be better .

Timbuck said:

Give that one away or burn it ....The next one will be better .

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Indeed! Looks nice hanging on the wall, anyway.

it could be the top itself or just the whole build in general. but it seems you already tried the low tension string option with no luck? was it fluorocarbons and what brand? not all flouros can create great sustain. try worths CL or Anuanue Clear Water (crazy good strings)
#2 try add sponge inside the ukulele body thru the soundhole. something like uposltry/mattress memory foam. cut a piece less then half the body and put it inside along the wall of treble side. it should create some massive sustain. OR not

hoji said:

ProfChris, wow.
Adding 5 - 6 grams of clay to the bridge:
More sustain
Less plunk/punch
Less harsh overtones
Less volume
Less "responsiveness"

Definitely worthy of more experimentation.

Click to expand...

Glad to be of assistance!

I think this tells you that the overall mass of the top + bracing was too low for sustain, and to control the jangly overtones. The proper fix for the future is either a thicker top, or heavier bracing, or a little of each.

You might want to try putting the same mass of clay at 3 or 4 spots on the top (maybe between the edges of the bridge and the sides, and an inch or so behind the bridge), rather than on the bridge, to see if that restores some of the volume and especially responsiveness. A heavy bridge takes longer to get the top working, and so reduces responsiveness. If so, adding some mass internally at the best spots could promote it from wall hanger

In the end, you're making trade-offs to achieve the best sound you can. If you look back at Ken Timms' posts you'll see that his tops are pretty thin and his bracing comparatively stout. My own tops tend to be thicker, but with lighter bracing. I'd say my ukes have a slightly faster attack than Ken's, whilst he achieves a fuller and richer sound (most would, rightly, prefer Ken's to mine I think but that's not the point, both ways work but produce some differences in the final result).

Bracing is interesting because it doesn't only stop the uke from folding up, it also controls the top's modes of vibration. If you ever find an old uke with no top bracing at all (and there are some around) you'll hear that it produces a lot of jangly overtones. So getting the placement of the braces right is also important - start by copying what's known to work!