12-string set-up blues

[Rick Homan]

A friend brought me a no-name, laminate 12-string for set-up. The fit and finish on it are quite decent. The action was so high as to be unplayable. The joint of the neck heel to the body looks solid: no finish cracks.

To date, I have:
1) installed JDL Bridge doctor to flatten the bellied top. It worked like a charm, and the guitar sounds great. I used the brass-pin version, because there is no place to drill a hole in the 12's bridge.
2) lowered the nut slots for .012 - .016 string height at the first fret.
3) tightened the truss rod as far as it will go -- I think.
4) shaved the saddle as to not much more than radius.

As a result, the guitar plays nicely in first position, but from about the fifth fret on the action gets high. String height at the 12th fret is 8/64" (3.175 mm) . My friend would like to have it play for fingerstyle all along the neck.

My options would seem to be:
1. Shave the entire bridge down so the saddle can be lowered further.
2. Do a "saw-sand-and-bolt" neck re-set." From its general construction, I am guessing this is a post-1970 mass-produced guitar, so removing the neck is probably not an option.

Any thoughts about getting that string height down? Thanks, in advance!

[Mark McLean]

Rick
This is the inescapable disease of the 12-string. Eventually they will all fold themselves in half under that string tension and disappear up their own soundhole. It sounds like you have already applied all of the reasonable remedies short of major surgery. It is probably a neck angle problem. If you run a straightedge along the neck does it fall well below the top of the bridge?

Options now?
1. Shave the bridge, but this is likely to have bad effects on intonation and tuning
2. Do the neck reset - probably an over-the-top option for a 30 year old ply guitar
3. Convince your friend that he needs a new 12-string
Good luck with it

Mark

[Rick Homan]

Thanks, Mark! With no strings, the straightedge slides right on top of the bridge. With all strings up to tension, it falls 3/32" below the top edge. I haven't seen this on a guitar where the heel-body joint appears solid; but, then, this is my first 12-string.

[Magnus Hultin]

I would say it is the belly rising rather than the neckjoint moving under string tension.
I have dismounted several laminated Sigmas from mid 70:s, they all had dovetail. If it looks like a normal neckblock and there are no plugs though it, i wouldnt be surprised if it is a dovetail.

One thing puzzles me regarding the bridge doctor. The way I have understood them (have never used one), they stabilised the bridge angle by means of a rod pushing against the end block. The result to my understanding is that the bridge is limited to only move verticallly relative to its resting position. Doesn´t this remove one important sound producing element, the rotation of the bridge caused by the longitudonal force in the strings?

I am not shure I would be able to hear the difference, but I imagine that there is a difference to the sensitive ear....

With the above in mind (if I am right) the optimal way to fix up a guitar with belly would be to replace the bridge, with one optimised to fit the shape of the soundboard (with the belly) but still with a top parallell with the direction of the strings.

Off course a neck reset would be needed in addition to get a proper action and stringheight over the top (in front of the bridge).

Please argue with me...;-)

[Antonio Cotichini]

I argue immediately, just to say that I agree almost totally with you Magnus. IMO the Bridge Doctor is a sort of horrible orthopaedic device that compulsorily affects the sound of the guitar. Not to talk about aesthetic problems due to the way it's attached to the bridge.
Almost no acoustic guitar is free from belly bridge, the point is HOW MUCH relief is to consider normal or acceptable. And about this should be interesting to know the opinions of the boys here around.
If a bridge bellies at the point that it bends deeply toward the sound hole (and it's not unglued, or the top broken) the problem probably comes from a weakened (X) bracing, due to whatever damage (hot, cold, bad wood, humidity, dryness, poor construction, yellow fever or malaria). The Bridge Doctor should be a crutch, but a crutch is a momentary help. If one needs it forever, will not run any more. I'm not talking about Rick's friend guitar (he is surely able to locate its damage), just about belly bridge and Bridge Doctor.
Anyway, that's my opinion.
Antonio

[Dave Yelverton]

Has anyone done any serious research on the effects of the JLD? I've used it on a few occasions and in all cases it has done the job it was advertised to do, i.e. removed excess bellying, counteracted bridge rotation AND with the added bonus of increasing the volume without radically affecting the tone. I'm not being partisan here; I trust my judgement and that of discerning customers.
The JLD works best when applied early, before bellying or rotation reach crisis proportions and should not be applied where there are structural faults. But I have to view the system as a little in advance of a temporary "crutch" if Breedlove and Taylor are prepared to use them as standard. If you look at the movement of the bridge and soundboard, it's a bit more complex than a simple rotation in the direction of the strings. I like to think of the JLD as a pivot around which everything moves. Unlike the violin, the guitar is very much a structural compromise. Put steel strings on and you compound the problem. Any innovation that allows you to mitigate some of the structural problems ought I think to be given serious consideration rather than dismissed out of hand.

[Antonio Cotichini]

Dave, Breedlove (I didn't knew about Taylor) build the guitar considering the JLD as part of it. So the whole project and relative bracing, stiffness... all the physics, is thought as a unique. When you add something to a still existing situation, even tempered in its own, you change it. In the case of the Bridge Doctor, you don't use it to reach a better balanced tone or a particular sound, it's just to treat and cure the disease of the belly bridge (why do they call it Doctor?), that's why I consider it a crouch, a way to try to save something that otherwise become useless. And it's ugly.
Are Breedlove and Taylor the only smart guitar factories in the market? Martin, Gibson, Larrivee, Collings and all the others are so stupid that they don't use JDL? Simply they reach stability and tone in a different way, with different construction methods.
But anyone is free to like whatever they like.
Antonio

[Jeffrey L. Suits]

You're mistaken. JLDs are not just to fix bellied guitars.

[Antonio Cotichini]

From Stew Mac site: JLD Bridge Doctor, a unique solution to a common bridge problem... providing leverage to flatten the soundboard.
Enhances volume and flattens "bellied" soundboard.
I'm not sure it enhances volume. For sure it flattens the bellied soundboard.
I remember also another orthopaedic device called Enancr (or something like that), which was advised and publicized on some guitar magazines years ago.
It was a strange shaped piece of metal to be positioned between the bridge pins and the saddle, under the strings. It promised to increase sustain. After a few months and after a test from one of the guitar magazines experts, disappeared.
And my question is: Would you put a Bridge Doctor on a precious Santa Cruz or Bourgeois just to "enhance volume" if it hadn't a serious "bellied soundboard"?

[Dave Yelverton]

Well, here's a case study. Customer brought in an ancient Epi which had sentimental vaue for him. He didn't dare put a higher weight of string on because of the bridge rotation and bellying. I examined it for bracing or bridge plate problems but these were sound although obviously not strong enough to resist distortion over time.I installed JLD under sufficient torsion to bring the belly back to 3/32 doming.. left for two weeks to allow to settle. strung up with the original weight. Already the guitar had considerably increased projection. I installed the heavier weight string, re-adjusted the JLD and returned the guitar to a very satisfied customer. His first comment was "Wow! it soundsw better than when I bought it." This is a guy who has been teaching guitar for the better part of 25 years and played in several bands and I have to respect his judgement.
JLD is a good cheap fix for lower end guitars. Customers are a little happier to be given a price for that rather than be told that the back has to come off and the braces/bridge plate replaced!
I quite agree that Breedlove design their guitars around the JLD. However Taylor don't but regard it as a good fix when their guitars belly. Of course you can wave the golden standard of Martin around but sadly even they are not immune; they have had major problems with bracing in the past. On the whole, because guitars rely on natural and to a certain extent unpredictable materials. no instrument can be guaranteed against belly/bridge distortion over the years. Bracing systems which guarantee this also guarantee a loss of tone. I would certainly hesitate on use a JLD on a high end instrument, but my sole reason is collectability. Restorarion brings in a whole new set of values and longterm functionality is not necessarily the highest priority.

[Jeffrey L. Suits]

Like I said: JLDs are not JUST to fix bellied guitars. You can quote all the catalog blurbs you want; I've installed dozens of them.

[Magnus Hultin]

I notice a typo in my first part above, it should end with "I wouldnt be surprised if it is NOT a dovetail."...

/Magnus

[Magnus Hultin]

What the heck, it was right from the beginning!
Disregard from my correction..., I must be getting old.