Quote:
Originally Posted by LemonCats
I've been wondering about intonation on nylon stringed guitars aswell
Skip to 4:20 (4 minutes and 20 seconds) or if you want to hear alittle bit about how steel string intonation is set in comparison to nylon start at 1:15 (1 minute 15 seconds) instead
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The information on how to setup intonation, and the differences between doing so on steel string and nylon string guitars, is somewhat misleading.
Frets are positioned based on an assumption of an "ideal" behaviour of vibrating strings. The discrepancy between the behaviour of real strings and the behaviour of "ideal" strings results in a guitar playing out of tune - having poor intonation. Specifically, that strings are stretched as they are fretted, which increases their tension, and hence pitch, and that they have increased stiffness towards their ends. (Another discrepancy is inharmonicity, which I won't get into, and wasn't mentioned in the video.)
To compensate for these factors, which result in the pitches being sharp, one increases the vibrating string length. How much to increase the vibrating string length depends upon a variety of factors, including, the type of string, the string tension, the amount the string stretches when being fretted - which is related to how high the strings are above the frets - and so on. Since each of the six strings is different, each requires its own, individual amount of lengthening to counter the fretted notes on that string playing sharp. That is true regardless of whether or not the strings are nylon or metal.
Nylon strings have less tension than steel strings. Fretting a nylon string increases its tension proportionately less than that for a steel string. Consequently, nylon strings, overall, require less lengthening than steel strings. However, thicker strings, generally, require more lengthening than thinner ones. That is, the thinner treble strings require less lengthening than the thicker bass strings. On steel string guitars, the second, B, string requires more lengthening than its two neighbouring strings. On nylon string guitars, the third, G, string requires more lengthening than its two neighbouring strings. That is a function of the strings used.
Intonation on a guitar will never be "perfect". However, it can be made, through successive approximations, as "arbitrarily close" as one wants to go to the effort to achieve. Guitars are made with varying amounts of attention paid to the intonation. On many - most - mass-produced guitars, the intonation is fairly inaccurate, but "close-enough" for many players.
Virtually all guitars have all of the vibrating string lengths lengthened. That is, the saddle is moved further away from the nut than the theoretical distance upon which the frets positions are based - the "scale length". What varies is by how much they are lengthened and whether or not they are "individually" lengthened. On most steel string guitars, in addition to the overall lengthening of the strings, the saddle is slanted, making the bass strings longer than the treble strings. This is a first-order approximation, acknowledging that the bass strings required more lengthening (compensation) than the treble strings. It assumes that the amount of required additional lengthening of each successive string is linear, which it is not.
On most nylon-string guitars, the saddle is not slanted and all of the string lengths are increased by the same amount. This assumes that each string needs the same amount of lengthening (compensation), which is not true.
The next level of intonation improvement is to use the same saddle, but alter where on the thickness of the saddle the strings break over the saddle. This acknowledges that each string needs its own amount of lengthening (compensation). However, the amount of individualization of the string length is limited by the thickness of the saddle material, typically 3/32". This can be done on both steel and nylon strings. On steel string guitars, one usually sees the bass strings break over the saddle towards the pin-edge of the saddle and the treble strings towards the sound hole edge of the saddle, but for the B string, which is as far towards the pins as possible. On nylon string guitars, the same arrangement, but, instead, the G string, rather than the B string, breaks as close to the tie block as the thickness of the saddle allows. Regardless, the thickness of the saddle does not allow sufficient lengthening of the B string, on steel strings, and the G string, on nylon strings, to fully compensate that string.
The next level of approximation is to use a wider (thicker) saddle, or split the saddle, to accommodate fully the amount of lengthening each string requires. This allows the bass strings to be lengthened as much as they need to be while also allowing the B or G strings to be lengthened as much as they need to be. (What was done in the video is an example of this.) In this case, each string breaks over the saddle where it needs to be to provide the best intonation.
Ideally, one attempts to have the intonation as accurate as possible in the areas of the instrument that are most played. For a steel string guitar, that might be in the first few frets. For a nylon string guitar, that might be over the entire range of the instrument. It depends upon the player and what his or her demands are for the music he or she plays. Although the most common method of setting up intonation is to ensure that the 12th fret notes play in tune, that ensures only that the 12th fret plays in tune. Ideally, in setting up the intonation, one sets it so that the areas of greatest playing are targeted for accuracy. That could be the first few frets, or the entire range of the instrument. Usually, the amount of individual string lengthening (compensation) is determined empirically for a specific type and gauge of strings, string height, and so on.
Then there is compensation at the nut, the next level of approximation, beyond this discussion.