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A classical and acoustic guitar setup guide.

5. Intonation

With everything about your guitar playing nicely, checking the intonation is next. If your instrument has been fretted properly, you may notice a slight increase in sharpness of each note as you ascend the fretboard. That is because as strings are depressed on the fingerboard, the various thicknesses of the strings will affect the downward distance the string travels before hitting the fingered fret. So, each string’s resulting length is partially dependent on that distance. Saddle compensation helps normalize effective string length. It’s not a perfect solution, but intonation is improved noticeably. This thickness/downward distance interplay challenge is best solved by having a compensated saddle length where the bass side of the saddle is moved back in relation to the other (treble side). You may notice that your saddle sits at an angle and that is because the bass side scale is extended relative to the treble.

  1. If you have read all the previous sections and fixed the issues, where needed, and are ready for the last tidbit of a professional setup, continue to follow these steps:
  2. Using a tuner app or device, bring all the strings up to pitch.
  3. Play a 12th fret harmonic (lightly touching the string but not pushing it down all the way to the fingerboard) on the low E string.
  4. Play that same string’s fretted note at the 12th fret (in this case you actually push the string down to touch the 12th fret). Is the fretted 12th note is a bit sharper than the harmonic you played in step 3? If the fretted note is sharp, then the break point of the saddle needs to be moved back. (if the fretted note is extremely sharper, then you have a more serious problem of incorrect fret location, saddle location).
  5. Use a piece of scrap guitar string a few inches long (from the high E ideally if you still have some pieces from restringing your guitar). If you don’t have any guitar strings you can cut a scrap piece from, find any sort of wire, fishing line, etc that relatively matches the thickness of that high E string.
  6. Beginning with the low E, release the tension of the string down enough so that you can place the scrap piece of string along the top of the saddle under the Low E (see illustration).
  7. Play a 12th fret harmonic (in tune, of course).
  8. Then play the note at the 12th fret using your finger.
  9. Is the note a little bit sharp? If yes, pull the piece of scrap string back (opposite direction/away from the headstock) just a tiny amount so that it remains on the saddle but is farther away nonetheless. Play the note at the 12th fret again. You’ll notice that it’s closer to pitch this time.
  10. Is it still a bit sharp? If YES, repeat the process of moving the scrap piece back until the fretted note plays in tune with the open harmonic. If your string happened to be a little flat, then move it in the opposite direction (towards the headstock).
  11. When the open harmonic and the note match perfectly, use a very sharp pencil to score a line on both sides of the scrap piece. Make your pencil as sharp as possible and score the line with its point butted up as precisely as possible against the string.
  12. Repeat these steps for all strings.
  13. With all of your markings done, release the tension on your strings until you can slide the saddle out of the slot.
  14. With the saddle out of the slot, use a file to remove material from the saddle in the direction of your pencil markings on both sides. This will establish the new break-point for your strings and they will play in tune in the higher frets.
  15. Round-over this new peak so that it’s not too sharp otherwise it will not be good to your strings. This is the new break angle for that individual string. Repeat this process for all strings.
  16. Congratulations! You have adjusted the intonation of your guitar!

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Final Thoughts

The first time I adjusted a guitar’s action, I felt like I had added $400 to its value. The difference was remarkable. I felt like a magician. But, guess what? It ain’t rocket surgery, as my friend Nichols used to say. Simply follow the sequence of steps I describe in this article and you’ll be able to feel the same thing I did when the owner played that guitar whose action I had just adjusted, her mouth open wide and eyes even farther. “It’s like a whole new guitar;” the best words any fledgling luthier could ever hear.

Bring your guitar to me if you need it to play well again but you don’t have the time to do it yourself. This process can take some time to develop. A year or so after I began researching the process and doing that first setup, I can go back and see my initial work with a fondness of those early days and excitement around learning this stuff. I was able to tweak those 1st instruments I worked on to make them better. Don’t expect perfection the 1st go! Best of luck!

Hart's Guitars' setup guide
Classical and acoustic guitar setup guide at Hart’s Guitars.

1 thought on “A classical and acoustic guitar setup guide.

  1. […] The lighter a string’s tension, the easier it is to press to the instrument’s neck or fret. The tradeoff is lower volume, and thus not too good for the campfire bluegrass session. If you’re on the quiet couch playing for your sweet thing or if it’s just you and Jesus….light tension strings might be your best guitar strings. This article will discuss briefly how to choose the best guitar strings. Then you’ll be ready for the perfect setup. […]

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