Adjust Acoustic Guitar Intonation

Most guitars have significant deviations from perfect intonation, often as high as 10% sharp on the lower frets of the sixth string. Unlike most electric guitars, the components of an acoustic are difficult to adjust without professional tools and experience. The key to the whole system is the strings' diameter, tension, and length from the nut to the saddle. There are many adjustments to these factors that will improve intonation, but absolute perfection is rare. Remember that most audiences will hear little to no problems.

Steps

First Steps

  1. Tune-an-Acoustic-Guitar. Most likely, you are tuning correctly and there is a legitimate problem with your guitar. However, it doesn't take much time to try a different tuning method. This is also an opportunity to confirm your suspicions: if the intonation is correct, plucking at the twelfth fret should produce a pitch exactly one octave above the open string. Confirm this with an electronic tuner for each string.
    • Some musicians reliant on digital tuners may benefit from learning to Tune a Guitar-by-Ear, for situations when a tuner is not available.
    • If your guitar has decent intonation but rapidly goes out of tune, you may need to replace the machine heads or the bridge.
  2. Change the string gauge. Your choice of strings affects your intonation, and Change-Guitar-Strings is one of the easiest adjustments for a layman to make. You can discover the appropriate gauge for your guitar by consulting a professional luthier or using an online guitar string calculator.
    • Different brands have different systems, so don't assume that every "light" string is the same gauge.[1]
    • Heavy strings may wear out your nut quickly, especially if it is made from weak materials.
  3. Replace worn frets. Many guitarists don't realize that replacing a seriously worn fret can make a much bigger difference than adjusting the nut.[1] If a string has worn a groove into the fret, take it to a luthier for a new fret.
  4. Adjust your truss rod. A warped neck can cause poor intonation, but unless there's an obvious problem, you're usually better off trying the adjustments above. You may need to adjust your truss rod if your strings buzz more easily on low frets than high, or vice versa. Look for a peg above the nut and adjust with a socket wrench, or a hole near or in the sound hole and adjust with an Allen wrench. Experiment until the string has an equal tendency to buzz at all frets when tuned.[2] Although truss rod adjustment is not as difficult as many musicians think, it is a good idea to make small adjustments at a time.
    • If you've never adjusted a truss rod before, ask a luthier for assistance or at least adjust slowly. Loosening will add relief (distance from string to neck), while tightening will reduce it. Extreme adjustments could damage your guitar.
    • You can also measure your neck arch by pressing the G string at the first and fourteenth frets, and looking closely at the distance between that string and the sixth fret. Most players will prefer a distance about the width of a medium gauge first string.
  5. Store your guitar safely. Always keep your guitar in a humidity range between 45 and 55%, and away from sunlight and heat. A professional quality case and regular use will go a long way toward preventing the warp and wear that can mess up intonation.

Adjusting the Nut

  1. Listen for improvements with a capo. Press a capo between the first and second fret, or just press down on a string with your thumb. If your intonation improves, it may be worth adjusting your nut (the piece at the top of the neck where the strings rest). If the different is difficult to notice, other methods will probably give faster and more noticeable results.
    • The nut is the most difficult part of the guitar to get right. Seek experienced assistance if any of the steps below seem beyond your ability.
  2. Shorten the string with a shim. Your intonation will be off if the distance from the nut to the twelfth fret is not equal to the distance from the twelfth fret to the saddle. If that first distance is longer (causing a sharp intonation), you can fix it by shoving a piece of bone or other nut material under the string, flush against the lower edge of the nut.[3]
    • If the distance from the twelfth fret to the saddle is longer (causing a flat sound), you may need to re-position or replace the tailpiece. This is a less common problem, and the repair may damage the guitar finish, so don't try this unless you're sure of the diagnosis.
  3. Press the string between the second and third fret. If you do suspect a problem, it's time to diagnose it. Begin by releasing the capo and placing it between the second and third frets. (Again, you may use your thumb if you don't have a capo.)
  4. Check the side of the string closely. There should be a tiny gap between the string and the first fret. If you can't tell if it's touching, tap the string just below the first fret. If there's a gap, you'll hear a click when the string hits the fret.[4]
    • You may need a magnifying glass or reading glasses.
  5. Raise a nut. If the string touched the first fret in the last step, the nut is too low. You can raise your nut at that string by gluing a piece of similar material to the bottom of the nut.[5]
    • Some guitarists glue a mix of superglue and bone powder or other materials into the groove instead. This is a bit risky, as it could affect the tone.
  6. Lower your nut grooves. If the gap between the string and fret was too large, you can gradually saw the groove that holds the string deeper. Work in very small increments and check visually as you go.[1]
    • The higher your guitar's action, the easier this is. More minor adjustments can be difficult and risks going too far.
  7. Troubleshoot nut shape. The nut may snag the string if the groove comes to a V-shaped point, or if the top of the string is below the top of the nut. Ideally, the nut should have a semicircular indentation, so the bottom half of the string rests atop the nut and fills the diameter of this groove. If the nut is too badly worn to correct this by hand, have the nut replaced by a professional.

Other Difficult Adjustments

  1. Check that the saddle lies flat and even. If the saddle's base is uneven, the strings may be supported at different heights, changing the intonation. You may push shims underneath the saddle to correct this, but this can make the saddle more fragile.[6] It's much more effective to compensate the saddle, but this repairs requires wood tools and the skill of a professional luthier.
    • To measure this, you'll need a cheap tool called a radius gauge. Place the radius onto the 12th fret, cycling through the gauges until you find a good fit. Now place that gauge on the saddle, after tuning your guitar. The tool should touch and mute both E strings, and get close enough to the middle four strings to cause a sitar-like buzz.
    • You can also measure string height with a ruler with <math>\frac{1}{32}</math> inch marks. The bottom of the low E string should be <math>\frac{3}{32}</math> inches away from the 12th fret, and the high e string should be <math>\frac{2}{32}</math> away.
  2. Install a pre-compensated saddle. If you want to try this yourself, you can buy a pre-compensated saddle that you think will adjust the problem strings in the correct direction. The results are usually not perfect, but the cost is lower than a professional repair, usually falling between $5 and $100 US depending on material.
    • You can also buy "blanks" and experiment in filing your own compensations into the saddle. Be sure to leave a sharp edge on the lower side of the saddle to stop all string vibration there.
  3. Reinforce the soundboard. In some cases, a weak soundboard provides an unstable surface for the bridge, knocking it out of alignment. This is a diagnosis and repair best done by a professional.
  4. Buy a guitar with non-standard frets. Some guitarists who want their intonation as perfect as possible claim that certain unusual fret boards improve the setup. Fanned-fret guitars are one example.

Tips

  • Different styles of playing calls for different setups. If you play aggressively, you'll need a higher action to prevent buzzing. This in turn may require larger adjustments to get the intonation right, or — in extreme cases — switching to another guitar.
  • Even expensive guitars often have intonation problems. If at all possible, test an instrument in person before buying it.

Warnings

  • If your acoustic guitar has a pickup under the saddle, do not attempt to adjust the saddle yourself. These pickups are very precisely positioned and fragile.

Related Articles

Sources and Citations

  1. ↑ 1.0 1.1 1.2 http://homepage.ntlworld.com/coleman005/intonati.htm
  2. ↑ http://www.frets.com/FretsPages/Musician/GenSetup/TrussRods/TrussRodAdj/tradj.html
  3. ↑ https://www.youtube.com/watch?v=ijBn6WvaUgg
  4. ↑ http://www.frets.com/FretsPages/Musician/GenSetup/NutAction/nutaction.html
  5. ↑ http://www.fretnotguitarrepair.com/repair/acoustic-guitar/nut.php
  6. ↑ http://www.frets.com/FretsPages/Musician/Guitar/Setup/MakeNewSaddle/newsaddle01.html
Retrieved from "https://kipkis.com/index.php?title=Adjust_Acoustic_Guitar_Intonation&oldid=299176"