A new type of bridge? Perfect intonation

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etkre

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Maybe this belongs in the Luthier section, but intonation is a concern for lots of us so...

I was getting frustrated trying to find a good location for the bridge on my banjo uke. Every spot was an unsatisfactory compromise intonation-wise, so I build one that could be adjusted:

picture.php


The bridge is maple and the individual saddles are bubinga. The only thing holding the saddles in place is string tension, but they're not going anywhere even with hard strumming and stretching. And the intonation is as good as the fret placements will allow - darn near perfect all the way up.

It wasn't difficult to build, and I'm guessing it would work well on standard ukuleles. Probably just pull out the saddle, fill the in the grooves and fashion some new saddles.
 
Out of curiosity, are the saddle placements in the picture where they had to be for the intonation you were after, or to show that they are adjustable? I wouldn't have thought such differences necessary, but I know squat.
 
The amount of compensation you need is pretty consistently a function of scale length. Bridges like that are pretty common on banjos and archtop and solid-body guitars.

It's probably way too tall, but I wonder how your uke would do if you took a Tune-o-Matic archtop bridge and reshaped the bottom to be flat.

--Mark
 
Out of curiosity, are the saddle placements in the picture where they had to be for the intonation you were after, or to show that they are adjustable? I wouldn't have thought such differences necessary, but I know squat.
Click to expand...

Those are the correct spots for perfect intonation on my uke. I raised the action a little too in the process to reduce some fret buzz, so those positions might be more extreme than on a uke with lower action.

how well does it drive the top?
Click to expand...

Are you referring to how loud it gets? Oddly, the uke got louder. I was expecting to have to carve out the underside to keep it from muting the skin, but all it did was dampen some of the overtones, which I like. Maybe the increased volume is just my imagination, but it certainly has a clearer and more focused tone. I would imagine that if this method was applied to solid tops, there would be no audible change in volume or tone.
 
Out of curiosity what is the distance from point A to point B
 

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One other solution I've seen is to dice the saddle up into pieces and shape each according to their respective string. You would use an extra wide bridge slot and a thick saddle and carve the peak accordingly. It's not fully adjustable like yours, but it allows "touch up" adjustments without having to start over with a new saddle.
 
Out of curiosity what is the distance from point A to point B
Click to expand...

Ron, there's about 5/16 of an inch between those lines you drew. There's about 5/32 of an inch total compensation (front edge of the C saddle to front edge of the A), that's with a string clearance of about 3/32 (maybe slightly more) at the the 12th fret when capo'd at the 1st fret.

Hope that helps,
Eric
 
I don't know much about these things, so cut me some slack:

Why would it need to be "fully adjustable"? Once they're in the correct positions for intonation to be correct, why would you have to move them again?
 
Ron, are you planning a solid top? Let me know how things go. I'd like to see this design evolve and spread into more acoustic instruments. Intonation issues seem to plague even high-end instruments because they can't compensate for all the different brands and string types.

Good luck,
eric
 
Why would it need to be "fully adjustable"? Once they're in the correct positions for intonation to be correct, why would you have to move them again?
Click to expand...

If I changed gauges, there would be different tensions. I believe tighter strings would cause more tension to be introduced when fretting and the saddles would have to be pulled back.
 
DaveVisi said:
One other solution I've seen is to dice the saddle up into pieces and shape each according to their respective string. You would use an extra wide bridge slot and a thick saddle and carve the peak accordingly. It's not fully adjustable like yours, but it allows "touch up" adjustments without having to start over with a new saddle.
Click to expand...

I did something like this on my resonator guitar. The bridge is two pieces of "dark" wood, each handling three strings. I filed the wood where each string crossed it to look like |\, /\, or /|. I did it by ear and by looking at other guitar bridges. It actually worked but took about four tries, each time filing a wee bit more where needed.

Overall, kind of a PITA, but I now have a low action, in tune reso that was only $150. Now if you add up the TIME I put into it . . .:eek:
 
etkre said:
Ron, are you planning a solid top? Let me know how things go. I'd like to see this design evolve and spread into more acoustic instruments. Intonation issues seem to plague even high-end instruments because they can't compensate for all the different brands and string types.

Good luck,
eric
Click to expand...

Yes, it's a solid top Eric. I'll be sure to stay in touch.
 
alec534 said:
I don't know much about these things, so cut me some slack:

Why would it need to be "fully adjustable"? Once they're in the correct positions for intonation to be correct, why would you have to move them again?
Click to expand...


On my main guitar I have two saddles, one for the summer and one for the winter. Even though I use the same type/brand of strings, there is enough difference between the seasons that intonation changes.

This may or may not be a problem with a ukulele, but even changing brands of strings can cause an intonation problem
 
You invented this:
Click to expand...

I've always wondered why you don't see those on acoustic instruments. I figured there might be sound transfer issues, or maybe its just tradition. It would certainly look out of place on a uke.:)
 
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