Resonator mandolin

A resonator mandolin or "resophonic mandolin" is a mandolin whose sound is produced by one or more metal cones (resonators) instead of the customary wooden soundboard (mandolin top/face). These instruments are sometimes referred to as "Dobro mandolins," after pioneering instruments designed and produced by the Dopyera Brothers, which evolved into a brand name. The trademark "Dobro" is currently the property of the Gibson Guitar Corporation. When Gibson acquired the trademark in 1993, they announced that they would defend their right to its exclusive use.

The resonator mandolin was developed in parallel with the resonator guitar. The resonator guitar was originally designed to be louder than conventional acoustic guitars. A resonator mandolin is generally somewhat louder than a standard wooden mandolin, and has a different tone quality and distinctive appearance.

Though resonator guitars are often played flat in the lap steel guitar style, resonator mandolins are almost exclusively played in the conventional manner.

The resonator mandolin was developed by John Dopyera, who sought to produce a guitar that would have sufficient volume to be heard alongside brass and reed instruments. In 1927, Dopyera and George D. Beauchamp formed the National String Instrument Corporation to manufacture resonator guitars under the brand name National, adding tenor guitars, resonator mandolins and resonator ukuleles to their product line within a year.

National mandolins were produced until 1941. The company also made resophonic mandolins sold under the Supro brand.

In 1929, Dopyera left National to form the Dobro Manufacturing Company with his brothers Rudy, Emile, Robert and Louis, Dobro being a contraction of "Dopyera Brothers" and coincidentally meaning "good" in their native Slovak language. This company primarily produced guitars, but also produced resonator mandolins and resonator ukuleles that employed a cone-and-spider resonator rather different from the one- and three-cone components of the Nationals. Dobro Manufacturing Company licensed designs and supplied trademarks and parts to a series of vendors such as Kay-Kraft, Harmony (Sears) and Regal. George D. Beauchamp retained control of the National String Instrument Corporation. The two companies clashed in court from 1931 until 1935, when the Dopyeras prevailed and the National-Dobro Corporation was formed. The company moved to Chicago in 1936-37.

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