Ovation guitars were an innovation when introduced in 1966. Their distinctive round backs stem from a theory that a semi-parabolic back would deliver a better balance of bass and treble tone. The company's engineers developed a glass fiber and resin material called Lyrachord that would mold to the shapes they calculated. The company is noted for further innovations with nonstandard guitar materials such as graphite and unusual sound-hole arrangements, as in their Adamas line of guitars.
Steel Six-String Guitars
Kaman Music, builders of Ovation guitars, use D'Addario EXP16 Phosphor Bronze strings on its guitars when shipping the instruments. These strings are lightly coated to resist corrosion and are considered a light string gauge for acoustic guitars, with diameters from 0.012 inches to 0.053 inches. Adamas 1818 Phosphor Bronze strings, in the same gauge, are also recommended by Kaman Music.
Twelve-String Guitars
D'Addario strings are also recommended for use with Ovation 12-string guitars, with the factory set being EXP38, gauged from 0.010 inches to 0.047 inches. This is also considered a light gauge, with the smaller maximum diameters a concession to the increased tension that the additional strings exert on a guitar. A similar gauge from Adamas would be the 1616 Phosphor Bronze set.
Nylon-String Guitars
Ovation's classical nylon-string guitars leave the factory with D'Addario Pro Arte EJ46 hard-tension strings. This set combines plain nylon treble strings with composite nylon core, plated copper wrapped bass strings. These strings exert a total of about 87 lbs. of pressure on the guitar, about half of what a steel-string set creates. For this reason, steel strings must never be used on a guitar designed for nylon strings.
Other Strings
Any gauge or manufacturer of strings may be used on Ovation acoustic guitars. Using strings of lighter or heavier gauge than the sets used at manufacture may require truss-rod adjustments to keep the neck of the guitar in the best shape for playing.