National String Instrument Corporation

1930 National Triolian resonator mandolin

The second company was formed by George Beauchamp, a vaudeville steel guitar player and house painter, and inventor John Dopyera, a violinist and luthier.

Dopyera had seen an amplified Stroh stick violin nearby with a small flat diaphragm and long attached horn. He used that initial idea, but with a large spun conical inverted speaker, to create his patented multiple resonator designs.

Dopyera was assisted with his nephews Paul and Carl Barth spinning the first aluminum diaphragms on wooden bucks. They first experimented with their novel ampli-phonic design in a large walnut console instrument. Soon afterwards the first German silver Hawaiian guitar was built by John and Rudolph Dopyera. This guitar, #101, was later modified with a mahogany Spanish neck for regular guitar playing.

Beauchamp had suggested to Dopyera the need for a guitar loud enough to play a melody over brass and other wind instruments.[3]

In 1927, National produced the first resonator instruments and sold them under their National brand. They had metal bodies and a tricone resonator system, with three aluminium cones joined by a T-shaped aluminium spider.

Brother Rudolph Dopyera, who previously worked with Weissenborne, hand built the original tri-cone models with diamond holes, prior to the second production stamped metal bodies by engineer Adolph Rickenbacher. They built metal resophonic mandolins, tenor guitars and ukuleles, some of which were ornately engraved with rose, lily of the valley and chrysanthemum designs.

Wooden-bodied Triolian and Trojan single resonator models eventually followed once the Dopyera brothers departed, based on inexpensive plywood student guitar bodies supplied by Kay, Harmony, and other established instrument manufacturers.[3]

In 1928, Dopyera left National, and with four of his brothers formed the Dobro Manufacturing Company to produce a competing single resonator design, with the resonator cone inverted. John Dopyera continued to hold stock in National. The Dobro design was both cheaper to produce and louder than the tricone.[3]

National soon introduced their own single resonator design, the "biscuit", which Dopyera claimed to have designed before leaving, though the patent was registered by Beauchamp. National also continued to produce tricone designs, which some players preferred.

In their 1930 catalog, National list eight key associates, including Adolph Rickenbacker, George Beauchamp, Harry Watson, Paul Barth, and Jack Levy.[4]

In 1932, the Dopyera brothers secured a controlling interest in both National and Dobro, and merged the companies to form the "National Dobro Corporation".