Guitar intonation problem.

My new guitar sounds great and in in tune except for the G string. As I go up the fretboard it starts to sound noticeably flat around the 12th fret. The other strings are fine though. Does anyone know what the solution to this problem would be? Is it Saddle, bridge, nut repair? How can a person fix that one string but not the others?

A qualified tech would move the saddle either forward or backward to adjust intonation. Such tech would probably use a high-quality strobe to measure pitch. And the tech would tell you that the guitar is a tempered instrument. It will never be perfectly in tune at every fret, but it can be made very close at most or all frets.

But, if it’s the 12th fret, no matter the temperament shouldn’t it sound always right?

It gradually goes out of tune up the fret board, I was wondering how they could fix the intonation on one string without messing up the intonation on the other ones.

The 12th fret harmonic will always be right (1 octave above the open string), but the 12 fretted note could be flat or sharp if the vibrating length of the string is too long or short - as was mentioned above this can be adjusted my moving the saddle. Most electrics have adjustable saddles so you can intonate each string individually (with a screwdriver etc), on an acoustic it’ll take careful shaping of the saddle (perhaps a new one) to make the adjustment.

BTW what kind of guitar is it, and what kind of strings? Wound or unwound G?

Larrivee L-09 Acoustic with Wound medium gage strings.

One other simple possibility I can think if is to check is if the saddle was maybe inadvertently installed backwards, after it was adjusted for height or something.

if you look at it closely the 4 wound strings should gradually shorten in length from low E to G, then there should be a pretty obvious transition, and the unwound B should be longer than the G - then the high E should again be shorter than the B. If that looks OK I think you’ll have to have a tech look at it.

I would suggest contact Larivee and discuss this. I would think their guarantee would apply if there is a problem beyond routine adjustment or a faulty string.

While there shouldn’t be a faulty string on a new guitar, it might be worth exploring the possiblity (cheaper and easier to try than anything else). G strings are typically the first to break because of their thin core; I’m wondering if this one somehow is unduly weak.

The Larivee website shows this model to have a compensated saddle. Typically these have compensation for the B string, but they are available with compensation for both the B & G strings. It’s possible a saddle with different compensation from what you have now would help.

I don’t see how it could be the nut, or the routine adjustments. It’s conceivable there’s a problem with the bridge (incorrect saddle slot angle), though I would find it surprising if there were.

To me, every acoustic guitar that does not have Buzz Feiten intonation requires the G string to be tuned slightly sharp to sound “right.”

Interesting. I long ago got into the habit of tuning G a bit sharp. I think at one time I had a conscious reason for doing so, but at the moment I don’t remember what it was. I do have a sense that it just works better that way.

Huh. Would this be worth trying on an electric?

Yep, the typical way to tune G is to match it to 4th-string-D-string-at-5th-fret or use a electronic tuner to match the G to exactly 196Hz. If one does that, the open G sounds fine but all fretted notes on that G string will sound “flat”.

I prefer to make the open G a little “wrong” (tune it sharp) so that the fretted notes sound a little more “right.”

It also depends on the style of guitar the player uses. If he’s mostly strumming open chords around the 3rd fret, he’s not going to notice that a lot of his fretted notes on the G-string are a little flat. If one plays the entire fretboard, then the sharp G compromise might make more sense.

I don’t do this on electric because they have individual saddles to get adjust the intonation more accurately. You can fine tune the intonation of the G string without affecting the adjacent D and B strings.

Acoustic guitar saddles are one piece of plastic with predefined bumps so you can’t adjust the intonation of the G string individually. Some acoustic manufacturers try to account for this with a “compensated” saddle but I find that you still have to tune the G string slightly sharp. YMMV.

My guitar intonation is incorrect. I am not an amatuer. The Twefth fret harmonic does not match the the 12th fret while fingered on the g string. It does on all other strings. Something is not right.

I bought the guitar used (in new condition though). I wonder if Larrivee will help me.

I would first verify that it has the correct gauge G string (it’s conceivable that a broken string was replaced with whatever was readily available) and that the string is in good condition.

With a good string, I can only think of three possibilities: a warped or crooked fret, a poorly cut or worn nut, or an improper saddle position. Of these, the saddle is the most common culprit.

It seems to me that such a fret problem would be very rare. I’m thinking it would have to be bent or worn such that it’s only out of place at the one string. Probably this could be checked with some sort of straightedge.

I could see a nut with a slot that’s worn or miscut affecting the harmonic. I wouldn’t think it would have the effect of increasing flatness as you go up the fretboard, but I can’t say I know – maybe it would.

In my observation saddles are the main focus for intonation concerns. Some compensated acoustic saddles I’ve seen have several variations off the straightline center, and I wouldn’t be surprised if even then there is some compromise from the ideal.

In poking around the web I’ve found something that suggests that Larrivee warrants only to the original owner. Nevertheless, I think it would be worth a phone call or e-mail to verify that, and to ask for any insight or advice they can offer. I’d also try to verify that the saddle on your instrument hasn’t been changed to a different design.

I think in the end, a hands-on inspection by a luthier will probably be the most helpful thing for you.