In the 1920s, the ensemble music of the day began to drown out the guitar. Trumpets, saxophone, and banjos all had a natural volume that simply was too much for guitars to stand up to. George Beauchamp, John Dopyera, and his brother, Rudy, joined together to design a mechanically amplified instrument. John Dopyera perfected a design utilizing three aluminum cones, Rudy suggested a metal body to enhance amplification, and the National tri-cone resonator guitar debuted in 1927.
John Dopyera left National in 1928 to develop a more affordable wood body guitar with a single cone and a spider-like bridge base. His new design was introduced under the name DOBRO® — a combination of Dopyera and Brothers. The Dobro trademark is now owned by Gibson. Guitars of this type, built by independent guitar makers, are referred to as resonator, or, resophonic, guitars.
Today, the instrument is available in a variety of permutations. Let’s take a look at some of them.
The most obvious difference is that resonator guitars come with two different kinds of necks, a round neck and a square neck. But why the difference? Beyond shape, the squareneck and roundneck differ in both the way they are played and the way the instrument is set up.
For instance, a squareneck is usually played in bluegrass. A roundneck most often can be found in blues, ragtime, or other forms of fingerstyle guitar. A squareneck is always played with a slide (due to set-up) where a roundneck is sometimes played without a slide.
A few other design differences include:
1. The squared off neck allows for more stable playing on the lap.
2. An extended nut raises the strings 1/2″ off of the fingerboard.
3. The tuning keys point upwards for easier tuning while playing.
4. The neck meets the body at the 12th, the traditional standard.
5. The headstock is slotted.
1. The round neck shape is similar to a standard acoustic guitar.
2. The action is slightly higher than on a standard acoustic guitar to allow for slide work, but much closer to a standard guitar rather than a squareneck.
3. The tuning keys are enclosed machines and pointed downward as in standard acoustic guitars.
4. The headstock is closed as is common on most acoustic guitars.
The body of a resonator guitar may be made of wood or metal. Each material has its own tonal characteristics. As a result, each is found associated with specific styles of music. The warm tone of a wood body fits very well with bluegrass and old time gospel or folk. The metal body’s tone is more closely associated with blues styles. Of course, these are generalities, not absolute truisms, and a combination of body material with bridge and cone choices create the final picture.
The combination of cones and bridge design define the largest portion of the instrument’s tone though.
A resophonic guitar may have one or three cones. The bridge and its contact with the cones transfer the vibration from the strings to cones to create the unique sound. Regardless of design, the cones act much like the speakers in a stereo.
Cones are made from aluminum, but the method of their manufacture is a very important element. Spun cones are machined to exacting specifications to ensure a superior tone. As a matter of fact, striking a spun cone produces a bell-like tone. A stamped cone is produced much like a car’s hubcap. That is, it is mass produced on a machine and stamped out using a mold. When a stamped cone is struck, the resulting tone is dead by comparison. This difference alone produces a profound effect on tone.
The single cone design often provides a louder volume than the tri-cone. On the other hand, the tri-cone design offers a wider palette of overtones and a fuller sound. The trade off in the tri-cone design is some lost bass response.
There are 3 main designs for bridges in a resophonic. The number of cones helps determine which is used. A single-cone design can use two different kind of bridges, the biscuit-bridge or the single-cone spider-bridge. A tri-cone design uses a t-shaped bridge.
The biscuit-bridge cone looks like an inverted speaker cone and is the simplest of designs. The small disc of wood that sits in the center of the cone is the “biscuit.” The saddle is also made of wood and is positioned in a pre-cut slot. Because of the single contact point in the cone, these resophonics tend to produce a strong tone but an uncomplicated one lacking overtones. The metal-body biscuit-bridge resonators are highly favored for delta blues players due to their loud, cutting metallic tone.
Spider Bridge on Single Cone
The single-cone spider-bridge design derives its name from the almost spider-like shape of the bridge. The cone is W-shaped, therefore the spider bridge contacts the cone in both the center and along the edges. As a result, string vibration is dispersed more evenly throughout the cone. The spider cone is more like a typical speaker in that its concavity is reversed forcing the sound out of the body rather than into it.
Whether a biscuit-bridge or spider bridge resonators is right for you depends on what kind of music you play. The biscuit bridge, single cone sound is closely associated with blues. The tonal qualities of the spider bridge, especially used in a wood body resonator, are most closely associated with bluegrass.
The Tri-cone has, as its name implies, three cones and a T-shaped bridge. These instruments are more difficult to build, so they tend to cost more than a single-cone model. The saddle of the Tri-cone sits in a slot along the long leg of the T. The shape of the bridge transfers the vibration to all three cones. In many ways, the tri-cone design offers tonal characteristics between the two single cone systems. The tri-cone design certainly offers more complex tones with a rich aura of overtones. Many slide players who straddle various styles prefer this style of resonator for its versatility.
Whether looking at a metal or wood body, a single cone or a tri-cone, or a roundneck or a squareneck, the rich choices of tone and playability are limited only by your style and tonal preferences.