Basic Intonation Question...open vs fret 1, 2, 3, etc

robbiej1959

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Every guitar I've ever owned or played, if you tune an open string, then fret a note on the same string, it will be sharp. If I press very very lightly this effect is reduced almost to nothing, but I don't think most players have that light a touch. So its finger pressure is driving the fretted note sharp.

So my question is why don't guitar makers change the fret location to flatten the fretted note slightly to compensate for an 'average' finger pressure? Or maybe 'sharpen' the nut position although I'm not sure that gives the same result.

I usually tune the guitar so the open strings are slightly flat and the fretted notes slightly sharp. This is the best solution I have found to make the guitar sound in-tune.

Most discussions around intonation center around adjusting the bridge to get the 12th fret and harmonic in-tune. Haven't heard anything on this exact topic although its probably out there somewhere.

I'm anticipating responses saying properly set-up guitars don't have this problem, but I am 63 years old and have been playing for about 55 years. Lots of different guitars. Electrics. Acoustics. Cheap. Expensive. Old. New. I find it hard to believe I've never played one properly set-up.

Thanks for your attention all!
 

Wayne Alexander

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robbiej1959, the intonation issue you describe is almost certainly due to the nut slots being too shallow. That makes the first few frets play sharp, aside from stiffening the action overall. If the nut slots are cut properly, you won't have that issue. Pretty much all mass-produced guitars come out of the factory with nut slots that aren't as deep as you'd want for easy action and to cure the intonation issue on the first few frets; take the guitar(s) to a luthier who can cut the nut(s) properly, or acquire nut files and learn to use them. You'll be happier I promise.
 

robbiej1959

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robbiej1959, the intonation issue you describe is almost certainly due to the nut slots being too shallow. That makes the first few frets play sharp, aside from stiffening the action overall. If the nut slots are cut properly, you won't have that issue. Pretty much all mass-produced guitars come out of the factory with nut slots that aren't as deep as you'd want for easy action and to cure the intonation issue on the first few frets; take the guitar(s) to a luthier who can cut the nut(s) properly, or acquire nut files and learn to use them. You'll be happier I promise.
Thanks...this makes some sense. I'll try it on an acoustic. I'm enjoying learning a but more about setups and light luthery. Would be exciting to tweak it and get a really well intonated guitar!
 

Joefish

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... first, welcome to the TDPRI

as our friends have noted ... you needed to get the nut squared away

and some folks go haywire with the saddle ...

me, I love my 50 year old Aria just the the way it is (... even with those screws in the bridge)
 

schmee

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I find if you properly adjust your nut slots this doesn't occur much.

As far as: "So my question is why don't guitar makers change the fret location to flatten the fretted note slightly to compensate for an 'average' finger pressure? Or maybe 'sharpen' the nut position although I'm not sure that gives the same result." Some makers use a ZERO FRET instead of a nut. My humble opinion is they all should.
 
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Freeman Keller

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Robbie, first welcome to TDPRI. Second, welcome to the question that has plagued stringed instruments from their very beginning. The causes of the problem and solutions are both very simple and very complex. Life is full of compromises.

First, the root cause of the problem is very simple, as you fret a tight string you stretch it. The frequency that it wants to vibrate at is a function of length and tension, both go up as you fret the string. The higher your playing action and the more force you put into fretting, the sharper the string goes. In fact it is very easy to calculate - if I know the mechanical properties of the string, the scale, the action height I can tell you how sharp it will go.

So, the first thing you can do is exactly what you say, get your action as low as possible (another compromise) and learn to apply the minimum fretting pressure, bring the string just down to the fretwire, don't choke it. Run lighter gauge strings (lower tension), play shorter scale instruments. More compromises.

The next thing that happens is that real strings have a certain amount of stiffness, they do not follow the ideal string physics model. What this does is shift the frequencies of the higher partials slightly upward. You can have your open A string tuned to exactly 110 hz but the partials will all be a few cents higher.

Nut and saddle compensation are not perfect but both can help with both the above problems - again, it is a compromise. Audiologist tell us that most people can hear 5 cents difference between two notes, very few can tell less. The 12th fret note/harmonic are a very easy way to do this, its just quick and dirty and for most people works "well enough". Compensating the nut can help too but to do it correctly the first two or three frets will be in the wrong place. Building a fretboard designed for a compensated nut is one answer.

Of course we know that the placement of the frets is a compromise to start with - it goes all the way back to the Greeks and our tempered scale. This has nothing to do with fretting the note, it just says that by compromising the location of all the notes (ie the string length at that fret) we can make each of the scales seem to play more or less in tune. More or less. If you only play in one key you can easily make a fretboard to play in tune, the minute you shift to another key you're doomed.

But as you also mention there are a few things you can do when setting up the guitar. I have a jazz playing friend who plays a lot of those fancy jazz chords with unpronouncable names. Often they involve frets way up the neck along with open strings. He askes me to intonate his guitars very slightly flatter than I normally wood - the 12th fret note might be two or three cents flat. He says "I can always sharpen the note when I play it, I can't make it flatter". He can hear that and adjust his fretting pressure, I sure as heck can't.

So, short story, there are some very good physical reasons why our beloved little wooden boxes play out of tune. There are some very real practical reasons why its hard to fix them. If you promise me that you will only play in the key of E or A or Bb I can move the frets and compromise the ends of the strings to make it play more in tune, but only in that key. Sorry.
 

Freeman Keller

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Let me add two comments to the above long rant. You posted this in the acoustic guitar forum so I will assume you are dealing with acoustic guitars. Acoustic guitars tend to have slightly higher action and stiffer strings than electrics (or classicals) so the frequency shift as you fret is more pronounced. However you also tend to play more in the first position where the effects are smaller. And its a whole lot harder to compensate an acoustic guitar saddle as you are doing the setup, its not like you can turn a little screw and make it flatter. My goal is always to be within that 5 cent mark, it works for most people.

And before we leave this topic here is a very good link to the theory behind why frets are locate where they are and how to deal with the problems that creates.


Mottola has some very good calculating tools that I use all the time when laying out fretboards and bridges on all kinds of instruments.
 
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nojazzhere

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Let me add two comments to the above long rant. You posted this in the acoustic guitar forum so I will assume you are dealing with acoustic guitars. Acoustic guitars tend to have slightly higher action and stiffer strings than electrics (or classicals) so the frequency shift as you fret is more pronounced. However you also tend to play more in the first position where the effects are smaller. And its a whole lot harder to compensate an acoustic guitar saddle as you are doing the setup, its not like you can turn a little screw and make it flatter. My goal is always to be within that 5 cent mark, it works for most people.
Please add that acoustic guitars rarely have saddles that can be adjusted INDIVIDUALLY to compensate for different string gauges. My first thought for the O.P. was that he needed saddle-work. I agree wholeheartedly with the advice about the nut, and sometimes finger pressure, combined with fret height, will cause notes to go sharp, but I would go there ONLY after the saddle issue is checked and corrected. ;)
 

Freeman Keller

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Please add that acoustic guitars rarely have saddles that can be adjusted INDIVIDUALLY to compensate for different string gauges. My first thought for the O.P. was that he needed saddle-work. I agree wholeheartedly with the advice about the nut, and sometimes finger pressure, combined with fret height, will cause notes to go sharp, but I would go there ONLY after the saddle issue is checked and corrected. ;)
Not only that but there are some highly prized acoustic guitars that actually have their saddle slots in the wrong location. Many of the infamous 1970's era Martins have the saddle angled but without any initial compensation. If you never go above the 5th fret you'll never notice.

It is actually not that hard to compensate an acoustic saddle so it meets the 12th fret/harmonic test. I will often leave the top of the saddle blank flat and lay a small piece of wire (a B string works nicely) on the top of the saddle. Move it back and forth until the harmonic matches, then mark that as the break point. Do it for each string, line up the break points, and bingo! I've used this trick to compensate 12 string saddles - they end up looking like a rip saw but play pretty much in tune.

And of course you can always split the saddle or do all those funky adjustable things that Gibson and others came up with. The ironic part of this critter is that it really had not been adjusted anywhere close

IMG_5082.JPG
 
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robbiej1959

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I find if you properly adjust your nut slots this doesn't occur much.

As far as: "So my question is why don't guitar makers change the fret location to flatten the fretted note slightly to compensate for an 'average' finger pressure? Or maybe 'sharpen' the nut position although I'm not sure that gives the same result." Some makers use a ZERO FRET instead of a nut. My humble opinion is the all should.
I agree and am surprised zero frets are so rare.
 

robbiej1959

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Let me add two comments to the above long rant. You posted this in the acoustic guitar forum so I will assume you are dealing with acoustic guitars. Acoustic guitars tend to have slightly higher action and stiffer strings than electrics (or classicals) so the frequency shift as you fret is more pronounced. However you also tend to play more in the first position where the effects are smaller. And its a whole lot harder to compensate an acoustic guitar saddle as you are doing the setup, its not like you can turn a little screw and make it flatter. My goal is always to be within that 5 cent mark, it works for most people.

And before we leave this topic here is a very good link to the theory behind why frets are locate where they are and how to deal with the problems that creates.


Mottola has some very good calculating tools that I use all the time when laying out fretboards and bridges on all kinds of instruments.
Great response. Thanks. It is acoustics mostly, although I certainly get the same issue with Teles. I've got a 70's Yamaha acoustic that I'll try to adjust at the nut and saddle. I want to pull the piezo pickup out and replace with a Pure Mini or similar, so I will have replace the saddle. I want the saddle higher so the notes ring nicely and it will be less sensitive to neck flatness. Then I can mess with the nut to reduce the open string/low fret position tuning problem. I'll try the book.
 

Peegoo

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A zero fret is not a good fix because they wear faster than a nut does unless the ZF is properly set up. And most all guitar makers that incorporate a ZF do not set them up corrrectly. On a ZF guitar, the depth of the nut slots is just as critical as on a guitar without a ZF; the nut does a lot more than simply maintain correct spacing between the strings. Zero frets are fiddly, but when correctly done they work great.

You can get really good intonation on most any guitar (acoustic and electric) by doing the following: gently press a string to the bridge side of the 2nd fret. Using good lighting and magnification, look closely at the point the string passes over the 1st fret. There should be the tiniest gap between the string and the top of the 1st fret.

If the string is touching the 1st fret, the nut acion is too low. If there's more than about .004" (the thickness of a yellow Post-It), the nut action is too high.

Use this method to adjust the depth of the nut slot for each string; the guitar will play easily and in tune better than it did before.
 

Freeman Keller

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Great response. Thanks. It is acoustics mostly, although I certainly get the same issue with Teles. I've got a 70's Yamaha acoustic that I'll try to adjust at the nut and saddle. I want to pull the piezo pickup out and replace with a Pure Mini or similar, so I will have replace the saddle. I want the saddle higher so the notes ring nicely and it will be less sensitive to neck flatness. Then I can mess with the nut to reduce the open string/low fret position tuning problem. I'll try the book.


Yeah, its a characteristic of any string instrument, stretch the string, it goes sharp. One of the problems with trying to move frets around (besides the fact that the sorta need to go in a straight line across the f/b) is that each string goes sharp at a different rate (Mottola discusses that). That is why the saddle on an acousitic looks the way it does (the B string notch) and an electric is different (the G string notch). Each string would require a different amount of movement from the calculated location - it simply is practical on a productions basis.

You probably know that old Yamahas are notorious for having bad neck angles which makes the situation even worse - you can't get the action down so its hard to play and goes sharp. I would suggest that before diving into your Yamie you measure it very carefully and decide what to do next.

What makes this even worse is that not only do they frequently need a neck reset, it is hard to do. Either Yamaha used a glue (some say epoxy) that does not come apart with heat and moisture or the dovetail is so tight that you can't get the steam in there - either way they don't just pop apart. I have a 1969 that I did the old saw off the neck and convert to bolt on and the action (and intonation) on mine is now very nice. We can talk more about this if you are interested.

And I will add that if you are considering nut compensation its very doable but there are some things to watch for. Most of the time people will make the nut overhang the fretboard on a couple of strings, this requires moving frets if you really want to do it right. The guitar becomes compensated for basically one string set, again, not a problem if you don't change. There is a good article in American Lutherie a while back about the theory of compensated nuts. There are also two companies that sell them - they do have patents on the concept (but I'm pretty sure you can still do your own).

The K&K Pure is my choice for acoustic pickups. They are passive and usually require a separate preamp or DI. I once asked K&K about running their pickup into an on board preamp that was already in the guitar - they did not recommend it because of impedance miss match. Worth a try however.

As long as I'm all wound up I'll add my opinion of zero frets. I think they are a great concept and if built into the guitar can work very well. The are a pain to retro fit and depending on your theory of how they should be set up they can be a bit of a hassle there. I happen to like low nut action but I want the bass strings a few thousands higher than the trebles at the nut, that is slightly tricky with a zero fret. I don't use them on my guitars but I don't really have anything against them. As Peegoo says, I would probably make it stainless
 
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Chiogtr4x

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Gotta say I'm a Martin owner ( '93 D-1) and a few buddies of mine that own 1969 D-28's, do the same exact same procedure with our guitars.

After tuning all strings open, to Standard,
do two things :

- we tune our B strings just a teeny bit flat, so that the 3rd fret D note ( we play a lot of bluegrass/folk/blues in C, G, D) is not sharp. It will be if you tune B string to pitch
- we tune our low E strings also a teeny bit flat, so that the 3rd fret G note is right in tune with the open G 3rd string. - lots of G chords ( or same chord form, with capo) in Bluegrass

>all is very predictable, it's not like the strings really sound flat when plucked open

* plus even when tuning flat, always tune UP to pitch! ( this is where headstock tuners really help pinpoint!)
 

arlum

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This is also where guitars with a zero fret come into play. Zero fret builds address and correct this issue. Then again .... zero fret guitars tend to sound a little different. Much like when using roller nuts ..... zero frets add a bit of brightness and subtract something I can't give a name to but still miss. 😕
 

dsutton24

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Now for the curmudgeon point of view. If fretting lightly fixes the problem, then fret lightly. If you have to move frets to compensate for poor technique, work on your technique. Same goes if your e string rolls off the fretboard, or you bang the selector switch when you strum, and so on and so on...

Learn to play any instrument you pick up. Way too many of us become slaves to an instrument rather than mastering it.
 




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