Ab thunk

pootsie

pootsie

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Hey all. I just discovered something odd about my uke. It has a nice ringing sustain all over the fretboard EXCEPT for any Ab. G and A ring out nicely on all the strings they go bliiiinnnng! when I pluck them.

But the fret in between them goes thunk. In tune, but thunk instead of bliiinnng.

Is this just a problem with the resonance that cannot be fixed? Is it the strings? I know it is not one particular fret because it happens to Ab anywhere on the fretboard.

Help help.
 

Here is a vid showing my problem (and my frustration!)

Please help :uhoh:
 
Thanks for that

I did some googling and it seems like it's kind of the opposite of a true wolf tone. odd. Instead of causing excess resonance, it's like a flat spot.

Right where I wanted to play ... :(
 
Hmmm. Interesting. I have the same Uke, and I totally love the way it sounds when I strum. However, I recently started playing around with fingerstyle, and I began noticing that G# (on every string) goes thunk instead of, as you say, bliiinnng. Same Uke, same note.

I have been thinking of locating a luthier to see if maybe the problem can be fixed or at least improved, but I haven't gotten there yet.
 
Yeah, it does seem to be an idiosyncrasy with that particular instrument.

I say that this is an opportunity to try some different strings or tunings! Maybe just tuning all your strings down a half step and see if the problem continues, or pick up some different tension strings (here's another plug for SouthCoast mediums or heavies!) and try tuning things down.
 
JamieFromOntario said:
I say that this is an opportunity to try some different strings or tunings! Maybe just tuning all your strings down a half step and see if the problem continues, or pick up some different tension strings (here's another plug for SouthCoast mediums or heavies!) and try tuning things down.
Click to expand...

Good thought. When I first noticed the problem I was using Worth Medium Browns, so I switched to some Worth Medium Clears that I had on hand. It didn't seem to make much of a difference, but they're pretty similar strings. I like your suggestion of experimenting with different tensions. I'll try tuning down, and if that seems to help, then maybe low tension strings will make a difference.
 
Really interesting. Sorry you're having this issue, but as a sound person who loves physics, it's really interesting!

It would seem to me that the resonance of Ab in that particular uke does not work with the way it's built. The fact that it happens on all strings in different places says it's the construction, and not the frets. Basically Ab is the opposite of the resonant frequency of the uke, and it just does not resonate!

I like the ideas of different strings, and tunings, but if the theory of the uke build is the issue, you will always have a problem with Ab no matter where you play it!

Keep us posted on the change of strings/tuning.
Good luck!
Skottoman
 
Skottoman said:
Really interesting. Sorry you're having this issue, but as a sound person who loves physics, it's really interesting!

It would seem to me that the resonance of Ab in that particular uke does not work with the way it's built. The fact that it happens on all strings in different places says it's the construction, and not the frets. Basically Ab is the opposite of the resonant frequency of the uke, and it just does not resonate!

I like the ideas of different strings, and tunings, but if the theory of the uke build is the issue, you will always have a problem with Ab no matter where you play it!

Keep us posted on the change of strings/tuning.
Good luck!
Skottoman
Click to expand...


I wonder if tuning up or down by a quarter tone would fix the problem. That way there would be no Ab no matter where you play on the fret board.

It would make playing with others a bit of a challenge...
 
I'd list this on the Luthier's Lounge. Sounds like something's keeping the soundboard from vibrating effectively at that frequency. Have you tried tuning up or down? I'd give it a shot. If you go with a half step, and the enharmonic equivalent (Ab at a different location) does the same thing, you know it's just such a deficiency of the instrument. Examples: Go up a half step and you can test the G string open. Down a half step and you can test the A string open. (I would try both)
If the problem continues at the Ab frequency, I would try tuning it in between. The problem may be sufficiently limited that there is a "sweet spot" somewhere in there. Of course you'd be stuck playing solo, unless you played with others willing to de-tune along with you.
One other thought, if you have a pickup on your instrument, I'd remove it and see if the problem goes away. If so, you know the culprit and you can either go without or try changing pickup style or brand.
No results, take it to a pro, for sure.
I'll keep an eye out. Please let us know what you find out, or don't find out.
 
Last edited:
I just experimented with the E string. When I tune down a half step, the thunk moves up one fret along with the Ab. And, predictably, when I tune up a half step, the thunk moves down one fret along with Ab.

No pickup to remove.

I'll keep an eye on Pootsie's thread on the LL.
 
cantsing said:
I just experimented with the E string. When I tune down a half step, the thunk moves up one fret along with the Ab. And, predictably, when I tune up a half step, the thunk moves down one fret along with Ab.

No pickup to remove.

I'll keep an eye on Pootsie's thread on the LL.
Click to expand...

So you also have a Mainland mahogany slot-head concert?
 
I fell in love with that uke online, and finally got to hold her in my arms at UWC this year. Oh, what a summer! What a romance!

There is that point in every love where the first blush fades and reality sets in.

I am still in love with that uke but we need to work on our relationship.
 
pootsie said:
I am still in love with that uke but we need to work on our relationship.
Click to expand...

I really love mine too, and I'm one of those rare monogamous ukulele players, so I won't give up on this one without a fight.
 
It sounds like you're getting some sort of phase cancellation. That would most likely be where two relatively flat surfaces oppose each other (so you get parallel reflective surfaces). The sound wave in question (Ab) meets its inversion in near perfect phase, and they partly cancel each other out.

The most obvious situation is that some point of rigidity in the top is the distance (wavelength) from the rigid back of some octave of Ab. The wavelength for Ab0 is 1320cm. So, reducing down geometrically, you're looking for parallel surfaces 10.3125cm apart, or a tiny bit over 4".

Jamie's suggestion of detuning slightly is probably your only solution, and as he says, you'll have trouble sounding in tune with others.
 
stevepetergal said:
Did you try between (higher than Ab but not G or lower but not A)? There may be a spot that works.
Click to expand...
Yes, I can definitely move the thunk around, which means I can, as has been suggested, retune/detune so that the thunk sits out of the way between halftones. Or I can just learn to live with it. Or I can try new strings. Or I can pursue it with a luthier--the guys in the LL are chiming in on Pootsie's thread about this same issue.
 
I've seen this happen even with solid body electric guitars where, even unplugged, there is just a completely dead note. As others have said, it's almost certainly related to the design of the uke, especially since you're seeing it on two of them.

I just checked my Mainland mahogany slot-head tenor and it is fine, but it is the one with a cutaway and rope binding (i.e. it's not the same model, really, at all).

John
 
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