weird tunning issue

Paulius Volkovas · October 2014

yes i just checked, fretted 12 and 12th harmonic are almost identical. Tuner is a bit jumpy so i say "almost", but they sound in tune too.

Jazzaferri · October 2014

definitely replace strings as next step.

Jon · October 2014

I'd still love to hear an answer for this from some of the luthiers around here. Very weird problem that I've had on several instruments. Intonation perfect at 12th fret, flat around 5-8ish. Shows up especially when playing octaves between the D and B strings, when it seems that the B is sharp, but actually the D is flat. Hasn't been a problem for me for a while, but still curious - it's an odd problem.

Al Watsky · October 2014

Intonation changes as the string wears.
If the string is old it will play flatter in the areas it has be severely worn.
If the string is new or only moderately used the intonation problem that is outlined above may be the result of a misplaced minus fret.
Thats the first fret after the spacing nut.
At any rate, its impossible to tell you without holding the instrument and examining every aspect of its geometry exactly why its acting in the way you describe.
The fact of the matter is that you may be pressing the string unevenly or too hard or too lightly. You may be mis reading your tuner. What ever.
Not that I am suggesting that .
There are too many variables to account for.
The OP needs to bring his instrument to a qualified repair and set up person who has experience with acoustic guitars.
This type of board chatter is pointless .
The instrument needs to be examined in hand by a professional.

Buco · October 2014

My guitar definitely intonates slightly worse with these Martin silk and steel strings I've been using lately. It's acceptable but not as good as before. At least I'm pretty sure it's the strings, nothing else changed and this is the first time I noticed any intonation issues since I have this guitar.
I just kinda split the difference and it's ok.