Page "Guitar" Paragraph 23

All three principal types of resonator guitars were invented by the Slovak-American John Dopyera ( 1893 – 1988 ) for the National and Dobro ( Dopyera Brothers ) companies.

Similar to the flat top guitar in appearance, but with a body that may be made of brass, nickel-silver, or steel as well as wood, the sound of the resonator guitar is produced by one or more aluminum resonator cones mounted in the middle of the top.

The physical principle of the guitar is therefore similar to the loudspeaker.

The original purpose of the resonator was to produce a very loud sound ; this purpose has been largely superseded by electrical amplification, but the resonator guitar is still played because of its distinctive tone.

Resonator guitars may have either one or three resonator cones.

The method of transmitting sound resonance to the cone is either a " biscuit " bridge, made of a small piece of hardwood at the vertex of the cone ( Nationals ), or a " spider " bridge, made of metal and mounted around the rim of the ( inverted ) cone ( Dobros ).

Three-cone resonators always use a specialized metal bridge.

The type of resonator guitar with a neck with a square cross-section — called " square neck " or " Hawaiian "— is usually played face up, on the lap of the seated player, and often with a metal or glass slide.

The round neck resonator guitars are normally played in the same fashion as other guitars, although slides are also often used, especially in blues.