Ladder-braced

Guitar bracing refers to the system of wooden struts which internally support and reinforce the soundboard and back of acoustic guitars.

Soundboard or top bracing transmits the forces exerted by the strings from the bridge to the rim. The luthier faces the challenge of bracing the instrument to withstand the stress applied by the strings with minimal distortion, while permitting the top to respond as fully as possible to the tones generated by the strings. Brace design contributes significantly to the type of sound a guitar will produce. According to luthiers W. Cumpiano and J. Natelson, "By varying brace design, each builder has sought to produce a sound that conformed to his concept of the ideal."

The back of the instrument is braced to help distribute the force exerted by the neck on the body, and to maintain the tonal responsiveness and structural integrity of the sound box.

Braces may be made from top woods (spruce or cedar), balsa wood or, in high-end instruments, carbon fiber composites.

This is the standard bracing pattern on the classical guitar, dating to the work of Antonio Torres Jurado in the 19th century.

In the 1970s, scientist Michael Kasha radically overhauled every aspect of guitar design to incorporate principles such as mechanical impedance matching.

The Australian guitarmaker Greg Smallman introduced guitars with an extremely thin soundboard, which is supported by bracing in the shape of a lattice. Smallman combines this with heavier, laminated back and sides with a frame. Smallman's guitars are used by John Williams.

Smallman's design was inspired by research by Torres who made a guitar with a papier mâché back and sides to show that the soundboard was the most important factor in guitar sound projection. Smallman also uses two 45 degree pole supports from the bottom to the sound board that transfer sound.

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Wikipedia