- May 6, 2004
- 10,889
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- Disclosures
- Independent Instrument Technician - Retired
Let's start by looking at the function of the nut (a.k.a. top nut or string nut). It has three functions:
1. To act as a terminus at one end of the vibrating part of the string
2. To set the spacing of the strings at the headstock end of the neck
3. To set the string height above the frets at the headstock end of the neck.
An exception to this list is found in the use of a zero fret, where the string vibration termination and string height are set by the fret and the nut is only used to set the string spacing. But let's ignore the zero-fret configuration for now.
To do those three functions well, the geometry of the nut needs to be just right. The material the nut is made from also affects its performance. Let's start by briefly looking at the nut material.
Typically nuts are fashioned from bone, synthetic bone, plastic or a metal such as brass or aluminum, or wood. Though each may have its own sonic quality, that characteristic is by and large only noticeable when playing an open string. The damping effect of the fretting finger on the string on the section of the fretted string toward the headstock will remove most of the string energy that would make its way to the nut. And if the nut receives no energy its sonic quality is irrelevant.
Then there is the effect of the mass of the nut. Brass will have a higher mass than bone of the same size. And the differences in mass will have an effect on how the neck vibrates from string energy. The effect is small, very small, but some believe that they can hear the difference.
Perhaps the most important consideration of the material used for the nut is its resistance to wear. As you tune a string you are dragging the metallic wire under tension through a nut slot that has very little surface area. Then you subject that small surface area to vibrations under tension. So it is important that whatever material is used it will stand up to that stress. To that end soft plastics are not the best choice, and though metals may seem to be advantageous, they do not necessarily stand up to abrasion as well some other materials.
When it comes to the functions of the nut, the first and most obvious is that of being a termination point at one end of the vibrating string. For the string to vibrate it needs to have two fixed end points, and the tuner post cannot provide an accurate enough termination point, neither in terms of string vibration length nor string height. The nut provides a specifically located termination point, but only if it is cut well. I'll get into that a bit later, but for now let's look at the location of this "termination point".
One way to look at the nut is as the start of the fretwork. The frets are spaced along the fretboard at specific spots that will yield the notes we want. And there is a mathematical progression to their spacing. The position of the nut in relation to those frets is determined by that mathematical progression. Or viewing it another way, the position of the nut in relation to the bridge determines exactly where the frets are placed. Without making any other changes, if you were to relocate the nut nothing would play in tune other than the open string (assuming you tuned the open string).
But it's not just the location of the nut that is important for tuning. How the nut slots are cut is very important. A diagram will illustrate the point.
The distance from the nut to the first fret is critical. But the nut has thickness - distance B is greater than distance A, so it is important that the vibration termination point is precisely established a specific point in the thickness of the nut. Typically the nut is placed so that the termination point is on the fretting side of the nut rather than the headstock side. But to make sure that the "witness point" (termination point) is there the nut slot needs to be cut right. Looking at it from the side of the neck, in cross section:
Here the string angles down toward the headstock. The string's vibration termination point is at A, the critical distance from the first fret. The nut slot is angled down toward the headstock to ensure that the point A is well-defined. If the nut were reversed, the witness point would be at B which is too far from the first fret:
If the nut slot is not angled at all, not only is the termination point vague, but the string will have a tendency to rattle in the slot. So angling the nut slot down toward the headstock is important in establishing the right position for the termination point of the string's vibration.
The next post will deal with the function of string spacing at the nut.
1. To act as a terminus at one end of the vibrating part of the string
2. To set the spacing of the strings at the headstock end of the neck
3. To set the string height above the frets at the headstock end of the neck.
An exception to this list is found in the use of a zero fret, where the string vibration termination and string height are set by the fret and the nut is only used to set the string spacing. But let's ignore the zero-fret configuration for now.
To do those three functions well, the geometry of the nut needs to be just right. The material the nut is made from also affects its performance. Let's start by briefly looking at the nut material.
Typically nuts are fashioned from bone, synthetic bone, plastic or a metal such as brass or aluminum, or wood. Though each may have its own sonic quality, that characteristic is by and large only noticeable when playing an open string. The damping effect of the fretting finger on the string on the section of the fretted string toward the headstock will remove most of the string energy that would make its way to the nut. And if the nut receives no energy its sonic quality is irrelevant.
Then there is the effect of the mass of the nut. Brass will have a higher mass than bone of the same size. And the differences in mass will have an effect on how the neck vibrates from string energy. The effect is small, very small, but some believe that they can hear the difference.
Perhaps the most important consideration of the material used for the nut is its resistance to wear. As you tune a string you are dragging the metallic wire under tension through a nut slot that has very little surface area. Then you subject that small surface area to vibrations under tension. So it is important that whatever material is used it will stand up to that stress. To that end soft plastics are not the best choice, and though metals may seem to be advantageous, they do not necessarily stand up to abrasion as well some other materials.
When it comes to the functions of the nut, the first and most obvious is that of being a termination point at one end of the vibrating string. For the string to vibrate it needs to have two fixed end points, and the tuner post cannot provide an accurate enough termination point, neither in terms of string vibration length nor string height. The nut provides a specifically located termination point, but only if it is cut well. I'll get into that a bit later, but for now let's look at the location of this "termination point".
One way to look at the nut is as the start of the fretwork. The frets are spaced along the fretboard at specific spots that will yield the notes we want. And there is a mathematical progression to their spacing. The position of the nut in relation to those frets is determined by that mathematical progression. Or viewing it another way, the position of the nut in relation to the bridge determines exactly where the frets are placed. Without making any other changes, if you were to relocate the nut nothing would play in tune other than the open string (assuming you tuned the open string).
But it's not just the location of the nut that is important for tuning. How the nut slots are cut is very important. A diagram will illustrate the point.
The distance from the nut to the first fret is critical. But the nut has thickness - distance B is greater than distance A, so it is important that the vibration termination point is precisely established a specific point in the thickness of the nut. Typically the nut is placed so that the termination point is on the fretting side of the nut rather than the headstock side. But to make sure that the "witness point" (termination point) is there the nut slot needs to be cut right. Looking at it from the side of the neck, in cross section:
Here the string angles down toward the headstock. The string's vibration termination point is at A, the critical distance from the first fret. The nut slot is angled down toward the headstock to ensure that the point A is well-defined. If the nut were reversed, the witness point would be at B which is too far from the first fret:
If the nut slot is not angled at all, not only is the termination point vague, but the string will have a tendency to rattle in the slot. So angling the nut slot down toward the headstock is important in establishing the right position for the termination point of the string's vibration.
The next post will deal with the function of string spacing at the nut.