A great acoustic guitar needs a top that is both stiff and has a low mass – a rare combination. Spruce and cedar both have it, allowing the guitar to vibrate in a musically pleasing way. However, this doesn’t automatically mean non-traditional woods can’t be used to make great guitars.
“Numerous famous luthiers have used low grade salvaged timber and non‐wood products to demonstrate that how a guitar is designed to exploit available materials is more important than using prime tonewoods,” luthier Trevor Gore wrote in his paper Wood for Guitars, published in The Journal of the Acoustical Society of America.
Luthiers have used timber salvaged from wooden pallets, distillery washback vessels, whiskey casks and construction grade pine to build guitars, says Gore, who built a guitar solely of wood taken from his renovated cottage.
The top of “The Shed” guitar was made from five pieces of radiata pine, which had a density 30% greater than Engelmann spruce but while being only about 65% as stiff, which limits the sound quality.
“Having said that, it will still blow most things you can buy in a shop off the shelves,” Gore wrote on his website.
The great Antonio Torres himself built at least three guitars with pine tops rather than high-quality spruce, which he used for the majority of guitars, according to luthier José L. Romanillos’ book, Antonio de Torres, Guitar Maker: His Life and Work.
New wood choices for guitar back and sides
Torres famously built a guitar with Papier-mâché back and sides, which many assume was a test proving soundboards are largely responsible for the sound quality of the guitar.
A modern take made by gluing together 40 layers of newspaper using a mold was built by luthier Walter Verreydt for the Leonardo Guitar Research Project. The project was set up to explore viable alternatives to traditional tropical woods, which are becoming endangered and more expensive.
The impressive sound quality of the guitar in the video below suggests the back and sides only play a minor role in the overall sound quality.
The Leonardo Guitar Research Project tested this further with an online survey that asked people to rate the sound of 16 different guitars. They were built to the same specifications with a European spruce top, but different woods for the back, sides, neck, fingerboard and bridge.
Rather than traditional Rosewood and Mahogany back and sides, they used Plane, Laburnum, Pear, Cherry, Cypress, Robinia (darkened), Walnut, and Maple. This made the guitars look radically different, as can be seen in the image below.
Yet more than one-third (36%) of the 226 survey respondents who listened to a track featuring sound snippets of each guitar said they couldn’t notice any difference in sound quality between guitars. Those who could identify differences weren’t consistently accurate.
“This test implies that neither group (Tropical or Non-Tropical) possesses inherently distinctive, readily identifiable sound qualities,” according to the project’s findings.
A similar test of steel-string acoustic guitars built with different back and side materials by researchers at the Lancaster University reached similar conclusions.
They commissioned six hand-made Fylde Guitars built with back and sides made from Brazilian Rosewood, Honduras Mahogany, Indian Rosewood, Maple, Sapele, and Claro Walnut.
“Overall, our results indicate the species of wood used for the back and sides of a steel-string acoustic guitar has at best a marginal impact on its acoustic properties and perceived sound, and that cheaper and sustainable woods can be used as substitutes of expensive and endangered woods without loss of sound quality.”
It all suggests there is no need to always look to the same wood species when more diverse species, particularly for the back and sides, can achieve the same effect.
