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I just found the below.
Reason I was looking was because I was busy practicing something and just happened to be looking at my tuner while mucking about around the 24th fret and noticed that it was flat. Couldn't understand because I know I spent a lot of time on setting the intonation on the particular guitar I was playing and I believed it to be as near as dammit to "intonation heaven" (not to mention that I very rarely look at my tuner while I'm playing but happened to be doing this today because I was gauging the accuracy of my string bends for fun). So there goes that ("intonation heaven" I mean)!!! LOL!!! A link to the original post (and thread) is below.
I have to say that this is first time I've ever seen anything like this. I also have to say that I have to agree 100% with the concepts discussed. Intonating the way indicated reduces the effect of a host of other oddities and anomalies such as those introduced by a floating tremelo as but one example i.e. the intonation errors (he refers to them at tolerances) are basically averaged out over the entire fretboard. As I say: makes perfect sense to me.
Link to original thread on Sound On Sound: https://www.soundonsound.com/forum/v...187746#p187713
Reason I was looking was because I was busy practicing something and just happened to be looking at my tuner while mucking about around the 24th fret and noticed that it was flat. Couldn't understand because I know I spent a lot of time on setting the intonation on the particular guitar I was playing and I believed it to be as near as dammit to "intonation heaven" (not to mention that I very rarely look at my tuner while I'm playing but happened to be doing this today because I was gauging the accuracy of my string bends for fun). So there goes that ("intonation heaven" I mean)!!! LOL!!! A link to the original post (and thread) is below.
I have to say that this is first time I've ever seen anything like this. I also have to say that I have to agree 100% with the concepts discussed. Intonating the way indicated reduces the effect of a host of other oddities and anomalies such as those introduced by a floating tremelo as but one example i.e. the intonation errors (he refers to them at tolerances) are basically averaged out over the entire fretboard. As I say: makes perfect sense to me.
My esteemed colleague Andy has dealt with a lot of the issues that could be wrong with your guitar, however lets assume for a moment that it isn't riddled with serious faults and concentrate on the issues that are common to al guitars, good or bad, and which we can do something about by the application of skill.
The initial issue you have highlighted - the intonation drift above the 12th fret - is one that is common to all modern guitars by virtue of their construction. It's not a difficult problem to solve, but it's hard to explain.
When we depress a string to the fret we stretch it and the increased tension causes a slight increase in pitch. We compensate for this by moving the saddle away from the fret to lengthen the string's sounding length, dropping the pitch by an amount which compensates for the slight increase in applied strain. So far, so good, I'm sure everyone's still with me at this point.
If you have a dead straight neck the string breaks from the fingerboard at something around half a degree. the gap between the string and the fret increases constantly and the applied strain rises continuously. The rate of increase is not exactly linear, but neither is the rate at which the compensation increases, which is logarithmic, in line with the fret placement. At the kind of displacements we are dealing with in stringed instruments there is more or less parity between the pitch increase from the applied strain and the compensation achieved by moving the saddle.
A dead straight neck however results in an action that is very high in the higher register of the fingerboard. To accommodate the needs of modern guitarists we harness the technology of the adjustable truss rod which allows us to introduce a controlled curve in the neck. What this allows us to do is curve the fret plane around the arc of space occupied by the vibrating string, allowing the action to be lowered at the bridge by creating space in the first quarter to one-third of the fingerboard. The effect of this is to cause the aspect angle of the fret plane relative to the string to level out with the fret progression from nut to fretboard's end, so that from the 12th fret onwards the fret plane is more or less parallel to the string and the gap between string and fret doesn't change very much. Because the applied strain is approximately proportional to the gap between the string and fret, then neither does the applied strain change very much, however the fixed lengthening of the vibrating string still represents an increasing percentage lengthening of the vibrating length.
If you read any book on guitar maintenance they will tell you that the intonation is set by measuring the fretted note at the 12th fret against the the harmonic at that point. If you do this however, because of the condition I have described above, the notes sounded at the higher frets become progressively flatter as they are now being overcompensated.
The trick is to reduce the compensation slightly for the higher frets and average out the error between the 12th fret and the higher ones. A skilled technician can do this by using the harmonic at the fifth fret as a reference for the fretted note at the 19th fret on the next string up. The intonation is correct when each pair of strings satisfies the following set of conditions
1) the harmonic at the 12th fret is the same as the note at the 7th fret on the next higher string
2 the harmonic at the 5th fret is the same as the fretted note at the 19th fret on the next higher string
3) the harmonic at the 12th fret on the higher string is the same as the fretted note at the 17th fret on the next lower string.
Basically all notes of any given pitch value should sound the same as all other notes of the same pitch value at all points on the fingerboard, or an octave apart, within an acceptable margin of error. It is usually possible to achieve this to well within the human difference limen (the smallest difference in a stimulus that we are normally able to perceive).
It's important that you do not use a digital tuner to set or measure the intonation of a guitar. The reason for this is that the human brain doesn't assess pitch in the same way as a digital tuner; we do not meter the frequency of a note any more than ours eyes measure the frequencies associated with red, green and blue light. Just as our brains assess colour using a highly subjective, relative colourmetric process, so do we assess pitch and tone using a pattern recognition process which informs itself using all the information in the string's harmonic spectrum. Vibrating strings are affected by a phenomenon called inharmonicity. This is the progressive sharpening of the higher harmonics as a result of the increasing stiffness of the strings as they become shorter and (relatively) fatter. This deceives our perception of pitch so that even if a string is sounding at the correct pitch for a given note, if the string's voicing contains a significant level of inharmonicity in the audible harmonic range we will assess its pitch as sounding flat, or occasionally sharp. This is a long-winded way of saying trust your ears, not your meter.
The initial issue you have highlighted - the intonation drift above the 12th fret - is one that is common to all modern guitars by virtue of their construction. It's not a difficult problem to solve, but it's hard to explain.
When we depress a string to the fret we stretch it and the increased tension causes a slight increase in pitch. We compensate for this by moving the saddle away from the fret to lengthen the string's sounding length, dropping the pitch by an amount which compensates for the slight increase in applied strain. So far, so good, I'm sure everyone's still with me at this point.
If you have a dead straight neck the string breaks from the fingerboard at something around half a degree. the gap between the string and the fret increases constantly and the applied strain rises continuously. The rate of increase is not exactly linear, but neither is the rate at which the compensation increases, which is logarithmic, in line with the fret placement. At the kind of displacements we are dealing with in stringed instruments there is more or less parity between the pitch increase from the applied strain and the compensation achieved by moving the saddle.
A dead straight neck however results in an action that is very high in the higher register of the fingerboard. To accommodate the needs of modern guitarists we harness the technology of the adjustable truss rod which allows us to introduce a controlled curve in the neck. What this allows us to do is curve the fret plane around the arc of space occupied by the vibrating string, allowing the action to be lowered at the bridge by creating space in the first quarter to one-third of the fingerboard. The effect of this is to cause the aspect angle of the fret plane relative to the string to level out with the fret progression from nut to fretboard's end, so that from the 12th fret onwards the fret plane is more or less parallel to the string and the gap between string and fret doesn't change very much. Because the applied strain is approximately proportional to the gap between the string and fret, then neither does the applied strain change very much, however the fixed lengthening of the vibrating string still represents an increasing percentage lengthening of the vibrating length.
If you read any book on guitar maintenance they will tell you that the intonation is set by measuring the fretted note at the 12th fret against the the harmonic at that point. If you do this however, because of the condition I have described above, the notes sounded at the higher frets become progressively flatter as they are now being overcompensated.
The trick is to reduce the compensation slightly for the higher frets and average out the error between the 12th fret and the higher ones. A skilled technician can do this by using the harmonic at the fifth fret as a reference for the fretted note at the 19th fret on the next string up. The intonation is correct when each pair of strings satisfies the following set of conditions
1) the harmonic at the 12th fret is the same as the note at the 7th fret on the next higher string
2 the harmonic at the 5th fret is the same as the fretted note at the 19th fret on the next higher string
3) the harmonic at the 12th fret on the higher string is the same as the fretted note at the 17th fret on the next lower string.
Basically all notes of any given pitch value should sound the same as all other notes of the same pitch value at all points on the fingerboard, or an octave apart, within an acceptable margin of error. It is usually possible to achieve this to well within the human difference limen (the smallest difference in a stimulus that we are normally able to perceive).
It's important that you do not use a digital tuner to set or measure the intonation of a guitar. The reason for this is that the human brain doesn't assess pitch in the same way as a digital tuner; we do not meter the frequency of a note any more than ours eyes measure the frequencies associated with red, green and blue light. Just as our brains assess colour using a highly subjective, relative colourmetric process, so do we assess pitch and tone using a pattern recognition process which informs itself using all the information in the string's harmonic spectrum. Vibrating strings are affected by a phenomenon called inharmonicity. This is the progressive sharpening of the higher harmonics as a result of the increasing stiffness of the strings as they become shorter and (relatively) fatter. This deceives our perception of pitch so that even if a string is sounding at the correct pitch for a given note, if the string's voicing contains a significant level of inharmonicity in the audible harmonic range we will assess its pitch as sounding flat, or occasionally sharp. This is a long-winded way of saying trust your ears, not your meter.
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