Intonation in acoustic guitars

[SamBlob]

The intonation on my acoustic guitar has gone off. The fretted 12th note on all strings is sharper than the 12th fret harmonic. How can I get it right? Would new strings solve this problem? Does the bridge blade (saddle?) need to be altered? If so, should it be shimmed, or filed down?

The guitar is a Yamaha FG-375SII. I believe the bridge blade (or saddle, or whatever it's called) is plastic.

Any help would be appreciated.

[Ed Rafalko]

HEya Sam! Loooong time no talk to! Hope you're alive and well and happy.
My first move would be to try a new set of strings. Ifit's still off, you'll have to adjust the saddle by filing it in such a way that the edge the strings pass over move back- AWAY from the headstock.
You should do this for each individual string, as opposed to doing it all across the top of the bridge saddle in one continuous piece.

Tonefiend will, no doubt, be along any minute to give you a blow-by-blow description of how-to.
It's possible your bridge has slipped a little off teh top of the guitar?

[SamBlob]

EdRaf! Complete with "teh"! ;) It's been too long, man! And Tonefiend is here too! Great!

I'll post an intro with how I'm doing these days. I'll say here that my road travels have got more stable and my finances have got less stable...

New strings tomorrow, then! I guess I'll try shimming it after that...

[Tonefiend]

Hey Sam.

Ed it's a simple fix. You just need to move the fixture offset on the saddle slotting tool which will move the saddle to the proper position. Then run a new bridge. ;)

Actually repairing acoustics is not exactly my specialty.
But I will chime in anyway! :) Hows the action? Is it possible the fretted notes are sharper because your having to push down quite a bit on the strings?
An acoustic will never be 100% intonated, and on that Yamaha who is to say the scale and bridge location are even right?
Another problem could be the neck angle is failing, or the top is bowing.
I agree with Ed try a new set of strings first, and if check intonation on a good tuner.
Another trick is to measure the distance between the nut and saddle. On the high E the 12 fret should be in the middle. On the low E it is 1/8 back. Yamaha might have a metric scale, not sure. But for instance if the nut to the 12th fret is 12 3/4 you will want to see the high e string cross the saddle at 25 1/2. this is the first thing I would check. If this is right the guitar is ok!

So blow by blow...
1.) New Strings
2.) Measure scale length
3.) Check on a GOOD tuer. Strobe preferred
4.) If it is off and within range of the saddle you could file it.
5.) If it is off and not within range, you will have to heed the motto: Rock and Roll is supposed ot be out of tune!

[DrewBlanc]

I had a bad intonation problem on my old wurlitzer. It had a pretty good belly (bow) behind the bridge and the bridge was starting to come up. I took the bridge off and reglued it and then installed a bridge doctor to take care of the bow. The intonation is now as close as I can hope for and the sound is better than ever. If that is the problem check out THIS SITE. (http://www.jldguitar.com/index.html)

[SamBlob]

Thanks for the replies! I'll change the strings on Saturday and see how it goes from there.

[SamBlob]

Actually, that should be singular... I took all the old strings off my acoustic and the nut fell off...

Gone for the Ponal bottle (BTW, Ponal is Henkel's brand name for white glue...)

Then again, since all the strings are off, this may be the perfect time to stick the internal microphone back on and not have it rattle around inside the guitar...

[DrewBlanc]

No, no, no, don't glue it!!! It should be just slightly snug but still pull out easily especially if there is a piezo under it. If it is too loose that could be a big part of your intonation problem but find another way to get it to fit right, like a new saddle. Even a shim would be better than glue.

[SamBlob]

The nut should pull out easily? First I've ever heard that... or did you think I was going to glue in the bridge saddle (or bridge blade as I call it)?

The nut and the internal microphone have both been glued on.

[DrewBlanc]

I guess I need to learn to read. :blush Sorry.

[SamBlob]

No problem.

BTW, after I glued the internal microphone in place, I tried it out for the first time. It does not work. No problem; at least it doesn't rattle around inside the guitar any more.

Immediately after I put on the new strings, I played the guitar a while. While the open chords and single-note runs were as good as I remember them to be, the barre chords were dull and lifeless with just about no sustain. One day later, they sounded good again. Ever experienced that?

[Hatfield]

My acoustics have minds of their own. One day they sound great -the next they don't.

I think they got mad at me after a gig one night.

I would try a set of D'Addario Lights on your acoustic. I've found those to be the best strings.