Acoustic Intonation Problem!?

Question

Ok so i am in tune with all my strings first of all and have nw strings on too. Now the Problem :

So my high e string is is in tune but when i go down it on the fretboard it keeps on getting flatter. Oh and When i do the 12th harmonic it is in tune and when i play the 12th normal its really flat but in tune when its play it open. All of the other strings are normal.

Answer 1

Hi Slash

Forget the rest of the intonation. A guitar is tuned like a guitar and called tempered tuning.

Once the guitar is in tune with a new set of string, you have to check the 12th harmonic against the 12th fret. If it is flat at the 12th fret, move the saddle towards the fingerboard.

If it is shart, move the saddle back towards the  tail end of the guitar.

don't forget that the neck has to be almost straight with only 1/16"

of distance between the string and the fingerboard. How you do this is to one finger on the 1st fret and another on the 12th fret and press down.

That is a straight line and what you do is look at the 7 fret and check the distance between string and fingerboard. If it's too much, than tighter the truss road by turning it clockwise. If the string touches while you press both ends, than you need to loosen the truss rod one full turn.

Keep doing this until you have proper clearance. When you look at the headstock and sight down the neck, it must only have a slight dip and this can affect the intonation if it is too warped, or too bowed.

Answer 2

If your guitar has saddles then use the adjustment on them. Given that you say "acoustic" intonation I expect that you are referring to an acoustic guitar - most of which don't have saddle adjustment - or individual saddles. I have seen this happen a few times on one string only. It can be a problem that even good guitar techs can't fix.

First thing - try a new string. It's not unknown for one string - even a new one - to be problematic (faulty manufacturing). It might even be worthwhile try a slightly different gauge.

Second, if your guitar does have a one-piece saddle, try replacing it. If you find that this makes some difference then you might need to have a specially modified saddle made up to completely correct the specific problem.

Third, make sure the nut is cut properly and is not worn.

While I have seen very expensive instruments plagued with this problem, the expense of fixing it is sometimes not worth the investment. Good luck.