Acoustic Guitar

Overview

An acoustic guitar is a fretted, six-string chordophone that produces sound without electronic amplification. The player plucks or strums steel strings, and the energy of the vibrating strings is transferred through the bridge into a hollow wooden box, which radiates the sound into the air. The pitch of each string is set by its length, mass and tension; fretting a string against the fingerboard shortens its vibrating length to raise the pitch. The dreadnought described here is a large-bodied flat-top guitar tuned to standard pitch, built from solid tonewoods and braced to balance volume against structural strength.

The sound originates at the String Set, six phosphor-bronze strings anchored at the bridge and tensioned across the body. String vibration is coupled into the Body Assembly, whose thin Sitka spruce Spruce Soundboard acts as the main radiating surface. The soundboard's stiffness and resonance are tuned by the internal Top Bracing, a scalloped X-pattern of spruce struts that controls how the top flexes. Rosewood back and sides form the rest of the resonating chamber, and the round sound hole lets the enclosed air mass contribute a Helmholtz resonance that reinforces the low end.

Construction

The instrument is built as two major sub-assemblies that meet at a glued joint. The Body Assembly is assembled first: the spruce top and rosewood back are bound to bent sides, with the Top Bracing glued under the top and kerfed linings reinforcing the seams. The Neck Assembly carries the ebony fretboard, the seated fret wire, the bone nut and an internal truss rod that counters string tension. Neck and body are joined with a dovetail, and the Headstock Assembly holds six geared tuning machines that set string tension. Strings run from the machines over the nut and saddle and anchor at the bridge, completing the vibrating length that defines the guitar's voice.