Kenny checks neck angle.
By Kenny Hill
Classical Guitar Set-Up
From ACOUSTIC GUITAR, 07/2006
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A guitar is only as good as it plays. The best sounding, most beautiful and most expensive guitar is of little use if it is too hard to play. And even an ordinary guitar can be your best friend if it's easy to play.
Guitar makers – even famous ones – sometimes neglect playability. There may be the assumption that a higher action somehow produces more sound. Some players and builders adopted the attitude that if your guitar seems hard to play, you should practice harder. But today's performers often don't accept that. Most professional and touring concert artists now insist the guitar to play very well, to be a friendly ally with the demands of guitar performance. This is true for amateur players as well.
The principles of set-up for classical guitars are basically the same as those for steel strings or electrics, but because of the different tensions, the fatter strings, and differences in the bridge and neck design, some of these principles need to be interpreted somewhat differently.
The technical elements that determine guitar playability and set up are:
- The neck angle, or pitch, in relation to the soundboard and bridge,
- The thickness and shape of the neck,
- The condition of the fret board and frets,
- The height and shape of the bridge bone, or saddle,
- The adjustment of the nut,
- The type and tension of the strings,
- The player's style.
1. The neck angle is built into the guitar, and there is not much the average owner can do about it. The top of the frets should project about into the middle of the bridge height. Normally a straight edge laid on the frets will give 4 – 5 mm clearance above the soundboard at the bridge. Or you can just sight down the edge of the fingerboard and see if it points to the middle of the bridge. If the neck angle is too high the saddle protrudes too much above the bridge, putting too much torque on the bridge, the top, and the strings at the bone. If the neck angle is too low, the bridge may have to be shaved down, or it may be impossible to adjust the strings close enough to the frets for comfort.
There are some remedies to a badly pitched neck, but those are surgical, and beyond the scope of this article.
2. Neck thicknesses and contour can make a huge difference in the comfort of a guitar's left hand action, but the guitar maker will have already decided this. There probably are as many opinions about this as there are guitar makers. My standard neck thickness is 21.5 mm at the 1st fret, and 24.5mm at the 10th fret. If the neck is too thick or too thin it will have a real effect on the comfort and playability. This is subject to the player's taste, and doesn't really affect the procedures for optimizing the string set up. But it does affect the net outcome.
3. The ideal fingerboard is not truly straight, but rather has a slight forward bend, called relief. The reason is this: when a string is in motion, it is curved. By having a little relief in the neck there is a tiny bit more clearance for the string to swing into without bumping into a fret. Even though this clearance is miniscule, it is enough to allow the string to be adjusted lower before encountering string buzz. Relief can be anywhere from around .003” to about .010” measured at the 7th fret, and in a perfect world there is more relief on the bass side than on the treble. If a neck is too straight, or worse – with a back bow - the strings have to be raised uncomfortably high to reduce fret buzz.
A truss rod makes simple work of providing optimum relief. Modern two-way action truss rods work very well. Although truss rods have been standard equipment for steel string and electric guitars for ages, they're just beginning to catch on with classical guitar makers. This is a welcome trend.
The frets must be in line with each other, that is, none should be higher (or lower) than its neighbors. This is checked using a short straight edge, checking that it doesn't rock on the middle fret of any 3 frets.
The frets should be nicely rounded and smooth on the top. This gives a clearly defined end to the string on a fretted note.
4. The height of the bridge saddle determines how far you have to push the string down to the fret, affecting the left hand playing effort and accuracy. It should be low enough to make it easy (and fun) to play, but high enough to avoid undue string/fret buzzes.
I measure the saddle height by laying a straight edge on the 1st fret and the bone saddle, and measuring at the 12th fret. This can also be measured without a straight edge by just fretting the string at the 1st fret, but since a string is flexible, and round, it's harder to get an exact measurement. My standard "average" height is 3.2 mm for the 6th string and 2.7 mm for the 1st string. These measurements can go lower or higher, depending on the player, and depending on the exact condition of the neck relief. More relief usually allows a lower setting with less buzz.
I also curve the saddle a bit, with the arc peaking on the 4th string. The purpose is NOT to accommodate a curved fingerboard, (it's not usually curved), but rather to accommodate the different motion of the strings themselves. The 3rd and 4th strings move more wildly, and have more tendency to buzz. By setting them a little higher, the better-behaved 5th and 6th strings can be kept at a more comfortable height.
The top of the saddle should be half-round in cross section – the same shape as the top of a fret. This gives a clearly defined end to the string, without causing undue wear at that point.
String-break is the amount of downward pressure on the saddle as the string crosses the bone down into the tie hole. There needs to be only enough angle so the string doesn't jump around on the top of the saddle. Too much angle is unnecessary, and can cause excessive string breakage, too much forward pressure on the saddle, twisting of the top, and other undesirable side effects. String break is really determined by the overall neck angle combined with the bridge design, which are determined by the builder.
5. The nut adjustment is important. If the nut is even just a little too high it creates extra tension in first position, and that can add a lot to the struggle of playing, not to mention its affect on intonation. If the nut slot is cut too low, the open string will buzz, and that buzz will go away when the string is fretted.
Nut adjustment is easy – measure it with feeler gauges. Strings 1 and 2 are set at .052” above the fingerboard, 3 and 4 are .054”, and 5 and 6 are .056”. This assumes a standard fret wire of .045” (?) high. If the first fret is lower or higher due to wear or design, these specs can be adjusted accordingly. Use a nut file to cut the slot down to the level of the feeler gauge. The slot should be filed back at the same angle as the guitar head. This gives a well-defined end to the string at the front face of the nut.
6. String tension is a matter of personal taste. I can't always sense the difference just by playing. The assumption that a higher tension string automatically gives more sound is not necessarily true. In fact, lower tension strings can actually allow a soundboard to move more freely. The right string tension and brand is a matter of trial and error, looking for the right combination for both the individual player and the individual instrument.
7. The player's style and technique is the final arbiter of action set up. Some players fixate on buzzes, and those players may have to live with a higher action. Some players want the action to be as low as possible, and they may have to learn to work around buzzes. The final adjustment will be a compromise between those ends.
Flamenco guitar styles are not nearly as buzz-averse as classical styles. In fact fret buzzing is part of the flamenco "growl." For a flamenco guitar I look for almost no relief in the neck, a low saddle setting (less than 3 mm) and shape the saddle so the bass and treble almost the same height.
The right string action on your guitar can make all the difference in the world. A good set up can help you be a better player instantly, and make it fun to keep practicing and getting better. A bad set up can present too much resistance, discouragement, and even cause some people give up because it's too hard. Don't give up! Just get your guitar set up right.
© Kenny Hill, Felton, CA, November 2005
An edited version of this article appeared in Acoustic Guitar Magazine July 2006.