Troubleshooting Guitar Intonation

[Spook410]

So.. if you have your bridge in more or less the right place and your open string and 12th fret are in tune across the strings, what might be the issue if, particularly on the high E, you are quite sharp at the bottom of the neck? Several cents, unusable sharp while the open string is dead on. When you tune say, the F# to be right, then the open E is quite flat.

Nut isn't binding, frets are not impinging, isn't noticeable on lower wound strings. B string some, E string far the worst. Wasn't able to find reference to this online.

Raised action just to make sure. No change. Frets are level. Bit of relief. Extra sharpness goes away incrementally as you go up the neck. Not sure what to try next.

[Para]

It sounds like the string slots in the nut are to high, try holding the strings down at the 3rd fret and check the clearance at the first fret, there should barely be any clearance at all.

[Spook410]

Thanks Para.. but the nut slots are pretty close to right. I feel no extra pressure fretting so don't think I'm bending the string up. It acts almost as if some of the lower frets were installed a bit off but that would impact the wound strings just as much as the unwound.

I'm about to take it to a good tech. Don't think I'm in Kansas anymore.

[neatomic]

match the 12 fret harmonic! to the fretted 12th fret note…make sure you press the 12th fret down as you would during normal play…if the fretted note is flat compared to harmonic move the bridge forward (toward the neck)…if the fretted note is sharp, move it back towards the tailpiece

with a moveable nonadjustable saddle wood bridge basically get the e's right and hope the rest fall in ok

nut slots too high was also good diagnosis…last would be trussrod not set correctly…do you have alot of bow in the neck??

but recheck intonation with 12 fret harmonic/12 fret fretted first

luck

cheers

[Spook410]

Thanks neatomic.. I rechecked relief, there's just a bit. Also overall intonation. With the high E harmonic and 12th fret E exactly matching, I'm showing a bit over 3 cents sharp for an F at the bottom of the neck on the high E while the open high E is in tune.

This is a new guitar. I'm beginning to wonder if there is something inherently wrong with it. With it intonated to high E, scale length on the E string is about 25.125 inches. Fret measures are the same as a 25" scale guitar that doesn't have this problem. No idea.. hope one of the local techs can figure it out.

[Para]

Check the nut slots if the slots are too flat the break point of the string can be anywhere along the slot length, for example the break point for one string might be right at the edge of the nut nearest the first fret another could be farther back making the intonation out. Ideally the slots should have a tiny flat spot at the edge nearest the first fret and fall away towards the machine heads, one way you can do this is to mark the bottom of the slot with pencil lead and then file the slot angling down towards the machine heads until there is just a trace of the pencil lead left on the front edge of the slot, rolling the file as you do it helps prevent string binding, finish off with a fine grit paper very lightly to take out any chatter marks in the slot hope this helps.

[Matt Cushman]

Are your frets properly crowned? If the frets are too flat on top from leveling this can effect intonation. This sounds like a problem caused by the frets. If the nut is the problem then only the open notes are effected and the fretted notes should be correct.

[jazzbow]

All good advice above. The poorly cut nut and too flat a fret top can alter intonation.

Setting up a guitar is a balancing act.

Pressing a string down too much or pulling or pushing against a fret alters its pitch, as does a high action.

Are the strings stretched in?

Badly made strings are also a factor.

One customer wanted me to use a brand called 'Robert Strings'. Only because they had bought a box load on the internet. After spending an hour trying to intonate these f#####g strings I clipped them off and put on a set of D'Addario and we were intonated in 5 minutes.

Spook, a guitar is an imperfect instrument as far as being in tune.

Older traditional stringed instruments and early 5 course guitars had gut string frets that were moveable and there were micro tonal notes as well, so for instance you had G, G#, Ab, A, 4 notes instead of 3!
Then you have the introduction of the standardised 12 notes in an octave including #'s & b's.
It is interesting subject early music, harpsichords tuned to play in specific keys.

Now where a guitar is concerned with fret placement and being in tune it's all a compromise. All we can do is to get close to being in tune as possible.

I used to flip my nut with everything having to be spot on in tune and then playing a chord at the 10th fret and then hear the G string in the chord is out. Waahhh!

So after messing around with action, intonation and neck relief I found this works for Archtops and my ears...

• Stretch in strings and have them taught but not up to pitch
• Measure top E (thin) string from nut to the centre of the 12th fret
• Measure the same distance of the Top E string from the centre of the 12th fret to where the top E meets the bridge/saddle
• Repeat the measurement for the Bottom E (fat) string but add 2.5mm to the length

Now the bridge is approximately in the right place.

• Set your preferred string action measured at the 12th fret and tune to pitch
• Check intonation, harmonic 12th and fretted 12th note of both E strings the same

And then....

• Check intonation, harmonic 19th and fretted 19th note of the A and B strings the same
• Retune the guitar

And most importantly...

• Tune the guitar in octaves like this...

Bottom E (fat) to pitch
Bottom E 5th fret harmonic to tune Top E (thin) string
Bottom E 12th fret harmonic to tune D string 2nd fret
D string 12th fret harmonic to tune B string 3rd fret
D string 8th fret to tune G 12th fret harmonic
G string 2nd fret to tune A 12th fret harmonic

Phew!

Also this vid on tuning in 5ths using chords is good too

Good luck boyo!

[AlainJazz]

I've had lots of issues with this in the past and have spent considerable time tweaking intonation. It's a balancing act really. I doubt highly that it's the nut if the intonation problems are past the 7th fret. I would definitely try a different set of strings. I once spent hours almost pulling my hair out, only to find out that the issue was with a bad string. People say this is rarely the cause, but I've experienced it. The next thing is the bridge itself. I've even had to get a sadowsky true tone somewhat further compensated. Roger set the intonation himself on my him hall, and he did it with an old (very accurate) Peterson strobe tuner. Make sure the tuner you are using really is accurate. I've seen differences between the turbo tuner and the Peterson iPhone app that were significant. The turbo tuner is much more accurate. I hope this helps.

[Spook410]

Update on this: Intonation problems not yet resolved. Had a competent tech look at it but no issues were identified. I've ordered one of these to see if that addresses things. Not sure I expect the bridge to sound very good, but with the range of adjustment that will establish if it can be addressed by a better compensated bridge.

[JazzNote]

Hmm, did you try with a new string, maybe with another brand (some companies run into production problems after replacing some their machines or changing the materials).

[MaxTwang]

Ran across a Gibson Nighthawk that had the nut slot too close to the first fret (or first fret too close to the nut). The front edge of the nut had to be cut back over 1/16" (full nut in the slot, cut back above the fingerboard). Guitar intonated fine with the modified nut.

On another note - Earvana makes a compensated nut for supposedly better intonation, anyone try those?

[jazzbow]

Update on this: Intonation problems not yet resolved. Had a competent tech look at it but no issues were identified. I've ordered one of these to see if that addresses things. Not sure I expect the bridge to sound very good, but with the range of adjustment that will establish if it can be addressed by a better compensated bridge.

This type of bridge works well for adjusting intonation and you get a bit of 'zing' from the metal to metal contact.


Same style of bridge with unconventional intonation placement


Maple bridge with fret wire saddle


A nice piece of work. Saddle is cut for different string height


Conventional bridge with dimentions


Plain G saddles for a fixed bridge on a semi and solid.


Same design for archtop.


Another fret wire bridge.

Has your tech checked the fret positions?

https://www.stewmac.com/FretCalculator

If it all checks out then I'd say a badly cut nut.

[oldane]

If the intonation problems are more pronounced at the nut end, I doubt that a new bridge will solve the problem. The reasons I can think of has already been mentioned: Strings too high at the nut. Badly cut nut. Acute upswing of the fretboard (relief) near the nut. If it is neither, fret spacing should be checked. If the fret spacing is off, it will require more surgery to get it right (a new fretboard with new frets).

BTW, that bridge with the metal saddles was much used on German guitars back in the 1960s (Höfners among others). I didn't like them too much because the saddles tended to slide in the grooves, though they can be fixed with a drop of glue. On the Höfner 456 I owned in the 1960s and 1970s, I replaced this bridge with an all wood Gibson rosewood bridge (there was no StewMac web shop back then).

[Spook410]

Thanks for all the information and comments. I have checked the geometry with a good steel ruler and nothing appears to be amiss compared to my many other 25" scale guitars that don't have this problem. I'm also going to try swapping the nut and strings which I haven't done yet (so many projects.. so little time). They are quality mass produced strings I've used on other guitars and so far I can't see how the nut could be involved unless it were way high (it isn't) since the nuts geometry relationship to the first fret is obviated once you fret a note. Still, planning to try all things but will swap one thing at once as it would be nice to isolate the issue.

Again.. as I keep learning new things from the boards insights, I very much appreciate the feedback as I hack and slash my way through learning to work on my own guitars.

[Jabberwocky]

Guess the bamboo equal temperament pitch pipes were a little off that day at the factory...They could use some calibration.

[Jabberwocky]

Then again context is everything; it would probably sound swell sitting in with this band:

[Dave70]

Hmm, did you try with a new string, maybe with another brand (some companies run into production problems after replacing some their machines or changing the materials).

I agree, first thing I'd do is try out a new string.

[Spook410]

Jabberwocky.. if you want to be a dick, feel free to do it somewhere else.

[JazzNote]

Jabberwocky.. if you want to be a dick, feel free to do it somewhere else.

i do appreciate a good portion of humor ... and enjoyed the clip a lot

[Para]

Jabberwocky.. if you want to be a dick, feel free to do it somewhere else.

And this post was neccesary!

[goatrace]

i do appreciate a good portion of humor ... and enjoyed the clip a lot

These girls are tremendous! This is the kind of generous exchange that makes the forum of such value. Thanks to all...

[339 in june]

Jabberwocky.. if you want to be a dick, feel free to do it somewhere else.

We love you, Jabba !

[Spook410]

Just to wrap this up, a more distinctly compensated bridge took care of the problem. Will probably use this as an excuse to experiment with some different types. Curious about bridges with larger bases though it seems there is not a lot of variation in what you typically find for sale.

Thanks to all with suggestions and education on this.

[jazzbow]

Just to wrap this up, a more distinctly compensated bridge took care of the problem.

Spook, would you mind putting up a picture for my reference please.

Ta.