Differences in Dobro Cones

Written by tim hesse
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Differences in Dobro Cones
Dobro guitars replace wood tops -- found in typical acoustics like this one -- with a metal cone. (Guitar image by TMLP from Fotolia.com)

Acoustic resonator guitars, commonly referred to as "dobro" or "dobro steel" guitars, use built-in aluminium cones rather than a wood top to amplify their sound. Acoustic resonator guitars come with cones in one of three design categories: biscuit-bridge single cone, spider-bridge single cone, and tri-cone. Each configuration produces a different timbre.

Biscuit-Bridge Single Cone

The biscuit-bridge single cone is the simplest design. This configuration features a single, concave aluminium cone mounted in the widest part of the body of the guitar. The cone sits in a round hole cut in the guitar and rests on a small ridge affixed to the inside of the back panel of the guitar. Biscuit-bridge single cones typically come in metal-bodied resonator guitars, but can be found in wood-bodied resonators as well. The metal-bodied variety is the loudest of the two and has a sharp, nasally sound most associated with the Delta blues. Biscuit-bridge single cones are typically matched with a rounded neck shape. National, Don Morrison, Regal and Epiphone manufacture biscuit-bridge single cone resonator guitars.

Spider-Bridge Single Cone

Spider-bridge single cones have bridges made of eight metal posts. These posts distribute vibrations received from the strings to all parts of the cone. Spider-bridge single cones are typically matched with a square neck shape and are most associated with bluegrass music. Resonator guitars outfitted with spider-bridge single cones are usually played sitting down. The player places the guitar body on her lap with the cone aimed straight up. National, Crafters of Tennessee, Dobro, Paul Beard and Regal manufacture spider-bridge single cone resonator guitars.


The tri-cone configuration features three cones connected by a T-shaped metal bridge. When the player strikes the strings, the bridge receives and redistributes the vibrations across all three cones. This gives the tri-cone resonators a more complicated sound, with additional overtones and harmonics not heard in the timbre of a single cone resonator guitar. The additional materials and more complicated construction make tri-cone guitars more expensive than their single cone relatives. Slide players in the Robert Johnson tradition may prefer the tri-cone sound. National, Don Morrison and Regal manufacture metal-bodied tri-cone guitars. The majority of tri-cone resonators have metal bodies, though Don Morrison does make a wood-bodied model.


Some confusion has stemmed from the fact that the Gibson Instrument Company owns the "Dobro" brand and with it the trademark to its name. Dobro brand resonators have spider-bridge single cones. Regardless, the term "dobro" can refer to any type of resonator guitar.

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