One of the key components of a guitar is the bracing that is attached to the inside of the top wood. Think of the braces as the vocal cords of the instrument - giving it a unique voice. In this section we’ll explore the different kinds of bracing used today and the way those differences affect the sound of the instrument.
Simply put, guitar braces are strips of wood, usually spruce, that are glued to the underside of the top of a guitar in a specific pattern. Guitar tops that are made of solid wood require bracing. braces provide strength to the top, which is a single piece of wood that has been bookmatched and shaved very thin. Without bracing the tension of the strings on the top would likely cause it to bend and, eventually, break.
In addition to providing strength, the braces affect the tone of the guitar. Heavier or thicker braces will transmit a different sound than thinner ones. More braces means the top moves less and that affects its sound. Some braces are carved to produce hills and valleys which further affects how that particular top produces sound.
The earliest guitars had gut (and later, nylon) strings which put very little tension on the top of the guitar. With the advent of steel-stringed guitars in the 20th century, the need for a more stable form of bracing arose. In addition, players often wanted an instrument with more volume that could compete acoustically with violins and banjos. Around 1930 Martin Guitars introduced the OM model with X-bracing. Two long braces cross in the letter X just below the soundhole. Additional smaller braces branch off from the two main braces (see diagram). Note also that there is extra bracing on the bass side of the top to compensate for the strength of the larger strings in that area.
The newest form of bracing comes courtesy of Taylor Guitars’ chief designer, Andy Powers. V-class bracing involves just two long braces forming a V that has the open section at the soundhole and the closed section at the bottom of the lower bout. A cross brace sits below the bridge plate and a few small “wings” come off the V at critical points.
According to Powers, V-bracing allows the top to move more uniformly which producers more volume and longer sustain of individual notes which stay more in tune with each other than on an X-braced guitar.
In the 1920s and early 1930s Gibson guitars was looking for a way to compete with less expensive brands out there. They introduced their Kalamazoo and Recording King lines featuring a less expensive form of bracing known as ladder-bracing. With just a few strips of wood glued horizontally on the top, these guitars produced a more treble-friendly sound favored by blues, folk and some country performers of that era.
Today some models of Waterloo guitars (made by Collings Guitars) feature this form of bracing in order to recapture the sound of that time.
Antonio de Torres (1817-1892) is credited with inventing this style of bracing that has been used most commonly on classical (nylon string) guitars for the last 150 or so years.
Fan braces are installed to more closely follow the grain of the wood which produces a warmer, more earthy sound for the instrument. When it was introduced fan bracing allowed the musician to produce a more dynamic range of tones and made the guitar a more versatile tool for performing. It soon became the bracing style of choice for gut-stringed guitars and is still the dominant style today on nylon-stringed instruments.
There are quite a few variations of fan bracing but they share the common pattern of a series of thin braces fanning out from the soundhole towards the lower bout of the instrument.
Archtop guitars (and modern mandolins) are typically made with either a single large X-brace or two parallel braces fanning out slightly from the soundhole. The older parallel style, sometime called Tone Bar bracing, produces a loud, driving sound appropriate for instruments used in large bands or ensembles. One of the deficiencies of this bracing is that it doesn’t support the warmer, bass end of the tonal range. Some builders compensate for that by moving the parallel braces a little further apart.