New strings to fix acoustic intonation issue?

Question

I have just purchased a second hand acoustic guitar: a Sigma 000MC-15E. The strings it came with tune fine but the high e string sounds noticeably out of tune even when played just at the third fret! After reading on here I'm thinking that the string gauge was maybe changed considerably from how it was setup in the factory and so new strings of a different gauge may fix it?

But why is only the high e string affected? Is it just more noticeable on high e? Should I get heavier or lighter strings? The high e goes flat when fretted, so I reckon a heavier gauge will bend the neck more lifting the strings off the fretboard and therefore make the strings sharper when played fretted?

Answer 1

You could try changing the strings - that particular guitar comes with D´Addario EXP16 Light (12-53) strings.

If that doesn't fix it, take it to a guitar technician for a full setup. If there are any issues, they should find (and hopefully fix) them.

Answer 2

I'm just speaking from a physics perspective, not an experience one. But I would think the thinner the gauge, the less the string will go flat as you go higher up. Imagine the resonant sine wave that a fundamental makes on the string as it vibrates up and down. The shorter the string (from being fretted), the more the thickness is going to want to prevent the string from bending (esp. at the ends), in effecting making the bump's shape that of a longer wave (i.e. of a lower pitch). If it were me, I'd try getting a thinner gauge and seeing if that does the trick. If you do the experiment, please let us know the result!

Answer 3

With a new guitar behaving like that, it ought to be straight back to the shop!

Try the 12th fret test first - the harmonics there ( on all strings) should be the same pitch exactly as the fretted 12th fret note. Of course, it could be as simple as the top string broke before you bought the guitar, and a different gauge one was put on. Ascertain what the correct gauge should be, and replace with that. Otherwise, back to the shop.