Yamaha Corp developed a wood reforming technology "Acoustic Resonance Enhancement" (A.R.E.), which provides wood with a tonal effect similar to changes due to aging.
Guitars made with wood processed with A.R.E. produce a "mellow sound" like a "vintage guitar" that has been played for 20-30 years, according to Yamaha. The company will release the L36ARE and L26ARE series, acoustic guitar lines using the wood processed with the technology for the face board, on June 1, 2008 (Fig. 1).
A.R.E. is a drying process to properly control temperature, humidity and pressure so that the properties of the wood are changed to those similar to a guitar played for years. The technology is applied to wood naturally or artificially dried to a moisture content of roughly 7%.
Specifically, the technology is designed to enhance the crystallinity of cellulose among three constituents of wood cell wall, ie, cellulose, lignin and hemicellulose, while hydrolyzing hemicellulose (Fig. 2). The process takes about 30 minutes.
(Lignin is a high molecular compound that deposits on the cell wall and causes lignification to harden the plant. Hemicellulose is a polysaccharide, which is insoluble in water.)
The process increases the Young's modulus and enhances the sound propagation speed. The wood processed with the technology produces the following effects when used for a guitar face board. (1) Sustain effect in the low range is improved, (2) rising level in the mid to high range is improved and (3) decay speed in the high range is enhanced (Fig. 3).
"Well settled," "mature," "warm" and "excellent resonance" were common terms used in comments made by musicians who played the new guitars, according to Yamaha (Fig. 4).
The face board used in the L36ARE and L26ARE series is made of softwood called "Engelmann SP" and is about 4.5mm thick. A.R.E. is applicable to materials other than wood and instruments other than guitar.
For example, the company is considering applying A.R.E. to violins because they use the same thin plates as guitars and many violinists wish to produce a mature sound. But it is likely to take some time before commercialization in both cases because strict conditions on temperature, humidity and pressure are required during the process.
The L36ARE and L26ARE series are priced at ¥378,000 (US$3,649, price may vary depending on country) and ¥304,500, respectively (both including tax). The prices of both series remain unchanged from the existing lineup. A.R.E. is conducted at Yamaha's Tenryu Factory (Hamamatsu, Japan), and the guitars are assembled by Yamaha Music Craft Corp.