Guitar Set Up
Guitar set up directly effects the play-ability of the instrument. An improperly set up guitar can cause all kinds of problems from being difficult to play to things such as fret buzz and string slap. Fret Buzz is that ugly sound a guitar makes when the plucked string is rattling on the fret or frets above it on the fingerboard. Anyone who has played a guitar knows this sound. It is not pleasant.
String slap is peculiar to classical guitars only. It is the slapping sound of the string hitting the fingerboard in front of the fret being played. It is usually evident when playing forte passages since the player is using more force on the strings. This sound may be alright on a flamenco guitar, but it doesn’t fly on a classical guitar. The main cause is the strings are too close to the fingerboard. The solution is usually to raise the action.
These things don’t just happen on cheap guitars. I have seen these problems on very expensive instruments. Fret buzz or string slap does not mean the guitar is bad. If the guitar was built properly it can be fixed and often without expensive repairs. There are many reasons why these things occur as you will read below. . Most times the fix is quite simple. A good part of the time the problem you can fix the problem yourself. You just have to know what to look for.
The Guita Set Up, Problems,Causes and Fixes
The Guitar Set Up Depends on Design and Execution
I build classical guitars so I will keep the discussion about design strictly about classical guitars. The numbers may be different for other types of guitars but the theory is the same. With a classical guitar the height of the strings above the top at the saddle is important. There is a range between 10-12mm that works best. This creates the best sounding instrument. Lower than 10 and the sound becomes muddy and the response slows. Higher than 12 and the sound gets punchy and the basses loose quality. The classical guitar bridge is designed to put the strings at right height and string break angle to make the guitar responsive. There is more about this in the guitar making video.
The distance from the fret to the string increases slightly from fret to fret up the fingerboard. The drawing illustrates this staircase effect created by the neck angle. The staircase effect enables the movement of the strings to clear the fret in front of the fretted note without hitting it. The difference in height from fret to fret is small. Therefore, if a fret is even slightly higher than the plane of the rest of the frets, fret buzz may occur. Some types of strings travel more than others and hence may require more clearance. The bass strings on a classical guitar travel quite a bit and therefore need more clearance than the treble strings.
The Purpose of the Neck Angle is to Provide Clearance
The purpose of the neck angle is to create a stair step effect from fret to fret as you move up the neck.. This stair stepping of the frets puts the next fret lower than the fret before it all the way up the fingerboard. This stair stepping is necessary because when a string is plucked it travels not only back and forth but up and down. Maximum motion occurs at the center of the effective string height. Therefore clearance must increase as you move up the fingerboard.
Incorrect neck angle will cause the strings to be either too low or too high. Too low and you get fret buzz and possibly string slap(classical guitars only). Too high and the instrument is difficult to play. The ideal height varies with the type of guitar and strings. If there is a problem and the neck angle is correct either the saddle, nut or frets will need work. Sometimes its all three.
The Effect of String Tension on the Neck
The force the strings exert on a guitar’s neck when they are brought up to pitch can be very large especially on guitars that have metal strings. This can cause problems. Well made guitars are designed to handle this force. If the problem is with the neck itself chances are you you will need a qualified repair person. The tension of the strings on the neck of a guitar is great enough to pull the neck forward slightly. The amount of tilt is typically factored into the guitar’s design.
The nylon strings of a classical guitar do not generate nearly the tension of steel strings used on acoustic and electric guitars but the effect is the same. The result of the tension pulling the neck forward is to bow the neck slightly. In other words the neck does not remain flat but will have a slight concave curve from the nut to where it meets the body of the guitar. This curve can be corrected to some degree with a truss rod or similar device built into the neck as in steel string guitars, but typically the neck on a classical guitar will have some slight curve to it. Classical guitars do not typically have a truss rod in them for a number of reasons. If the wood for the neck is carefully selected and the neck properly constructed it should not need one.
Problems, Causes an Repairs
There can be many potential problems with the guitar’s set up. Some can be easily fixed. Some should be tackled by a qualified professional guitar repair person. Repair people see these types of problems all the time and have a lot of experience with this. Some of the most common causes are outlined below.
Improper Neck Angle
Improper neck angle is caused by a poorly designed guitar or one that has not been constructed properly. In the worst case both are true. If you have some experience you can sight down the neck and see if the neck angle is correct. An inexperienced person should have a professional take a look. A professional repair person will be able to tell in a flash. If the neck angle is incorrect the fix can be complicated and should only be done by a qualified professional.
Warping or Twisting
Necks are made of wood. Only stable quarter-sawn wood should be used for a neck. If there was a bend in the tree in the section the neck blank was cut from it will have a tendency to twist or warp. This is true even if it is quarter-sawn. This is probably the most serious problem. This wood should not have been used to make a neck in the first place. Poor wood selection is typically the result of an experienced guitar builder.
Warping or twisting causes problems because it changes the plane of the neck. Depending on how severe the problem is a truss rod adjustment (if your guitar has one) may not work. This type of problem is not easily repaired and is best done by a qualified professional.
String Height Too Low
All players want the guitar to be easy to play. This is achieved by getting the lowest string height possible. On a classical guitar this can cause problems. Even if there is no fret buzz there will likely be string slap. It may also be difficult for the player to execute crisp pull-offs or hammer downs. For a classical guitar the string height for the 6th string on the bass side should be about .155″ or 4mm at the 12th fret. The height on the first string on the treble side at the 12th fret should be about .010″ or .3mm lower or .135″ which translates to about 3.5mm.
A common result of having your strings too low is fret buzz. Make sure that the string height is appropriate for the type of guitar and the type of strings you are using. The height will vary with both. Classical guitars have a higher minimum string height because of the type of strings used and the techniques used to play teh intrument. They also have the steepest neck angle since this provides more clearance up the fingerboard. Typically electric guitars have the lowest minimum height, hence the lowest neck angle.
The easiest fix is to raise the string height. This will involve raising the saddle height or possibly raising both the nut and the saddle. This may require making a new nut or saddle, or both. If the height is appropriate for the type of guitar, the neck angle is correct and there is no warping or twisting, high frets are most likley the problem.
If your string height is within reason then you need to start checking for high frets. This is the most common cause of fret buzz and it can be easily fixed. A fret as little as .001″ – .002″ can cause fret buzz. If there is one or more frets sticking up above the plane they can cause your string to buzz.
The high fret or frets must be found, leveled and redressed. This can be easily leveled with the Buzz-Off® Fret Leveling Kit. Watch a video demonstrating how to use the Buzz-Off® fret leveling kit to find and level high frets. The kit will work on any type of guitar. Electric guitars can have more frets so an extra dowel is included in the kit and is necessary to check for level on the upper most frets. J.S. Bogdanovich Guitars also offers a kit for ukuleles and mandolins which works on wide range of instruments.
Sometimes frets behind the fretted note will buzz creating a back buzz. This is a slightly different sound than typical fret buzz but equally as annoying. The string movement behind the fretted note is caused by sympathetic vibrations in the string. This kind of buzz could be a sign that the nut is too low or there is not enough neck angle. But it is caused once again the string hitting the fret behind the fretted note. After first checking the nut and the neck angle it may be possible to correct this by either raising the nut or lowering the high fret behind the fretted note.
Fixing Fret Buzz
Most times the problem is something simple and easily fixed like a high fret. If a fret was not seated properly when it was installed it will stick up a bit. A fret only has to be a couple of thousandths of an inch too high to cause fret buzz. High frets can be fixed without the need for a repair person or expensive devices and equipment. This type of problem can be easily fixed with the Buzz-Off® Fret Leveling Kit. Watch a demo on using the kit.