As the acoustic guitar became popular in the early 20th century, players needed ways to increase the volume of their instruments so they could be heard when playing with other musicians in large performance spaces. In the mid-1920s, John Dopyera developed an amplifying system, which he used when he founded the National String Instrument Corporation in August 1926 with his brothers Rudy, Robert, Louis, and Emil. Their company would use Dopyera's system to produce “ampliphonic” or “self-amplifying” guitars, known today as resonator guitars. John received a patent for his design on December 31, 1929.
More-advanced designs soon followed, including one which utilized a single aluminum cone to turn the entire guitar into a speaker cabinet. The guitar strings sat on a thin wooden saddle (or “biscuit”) at the peak of the volcano-like aluminum cone. The biscuit transferred the vibrations of the strings to the speaker cone, which would then resonate, thus amplifying the sound.
John, however, did not think that this single-cone design was well-suited for guitars, since they were so much larger than ukuleles. In frustration, he resigned from National in February 1929 to found Dobro Manufacturing; he derived the name “Dobro” from the first letters of Dopyera Brothers. Dobro modified National’s biscuit design by flipping the cone upside-down and connecting the broad base to the strings with a four- or eight-armed “spider”; unlike the biscuit, the spider conducted the vibrations from the strings directly to the edges of the speaker cone, allowing the cone to vibrate freely.
In addition to the cones, Dobro bodies featured sound holes between the resonator and the neck; in every model except Model 35, which featured segmented F-holes, these sound holes were circular and resembled the portholes of a ship. Because of its overall design, Dobro resonator guitars had longer sustain than single-cone Nationals of the same period.
In fact, the sound of these vintage Dobro guitars much more closely resembled that of the tri-cone or tri-plate National resonators, which, as their name suggests, had three resonator cones, rather than just one. Each resonator cone was six inches across, and the three were arranged in a triangle with two on the bass side and one on the treble side of the body. The three peaks of the cones were connected with a T-shaped bridge topped with a wooden saddle, which allowed all three cones to vibrate in unison, thus amplifying the sound.
As with nearly all resonator guitar designs, these cones were hidden under a sound plate, which were sometimes engraved for artistic effect. Because the vibrations had to travel farther from the bridge to three cones than in single-cone designs, tri-cone guitars were not as loud as single-cone guitars, but they boasted longer sustain and a sweeter tone.
Dobro and National merged in 1935 to form National-Dobro, but by the late 1930s resonator guitars had become less popular, as electric archtops and steel lap guitars became more accepted. National-Dobro made its last resonator guitars in 1940 0r '41. The company continued to sell a few models into 1942, when National-Dobro reorganized as Valco under Vic Smith, Al Frost, and Louis Dopyera...
Today, collectors can find resonator guitars under a variety of brand names besides National, Dobro, and National-Dobro. For example, Dobro built instruments which other distributors like Ward, for Montgomery Ward, sold under their own brands. In 1932, Dobro granted a Chicago-based company named Regal a license to manufacture guitars with a Dobro resonator, and in 1966 Mosrite purchased Dobro and began to produce resonator guitars under the brand Replica 66.
Dobro and National themselves produced a wide array of models and styles, but unlike Martins and Fenders, vintage Dobro guitars are a headache to date with much accuracy. For many years, Dobro model numbers corresponded to prices in the Dobro catalog. As a result, the same guitar could be listed under different model numbers in different years, and multiple designs could be listed under the same model.
Model 45, for example, simply meant that the guitar cost $45. By far the most collectible Dobro, however, is Model 206, only three of which are known to exist today. The instrument's design featured gold-plated and engraved hardware, with a gold sparkle in the center of the body. Most Dobro models were more modest, especially with the onset of the Great Depression.
National manufactured a variety of models in both the single-cone and tri-cone styles. Some of these models featured wood bodies, while others were metal with nickel-plating. These nickel-plated National guitars are extremely collectible for both their excellent sound and their dazzling look—those with round necks allowed different techniques than those with square necks, which are most desirable.
Single-cone National models included the Triolian, Duolian, Style O, and Style N; tri-cone models included Styles 1, 2, 3, and 4. Style 1 was simpler, while Styles 2, 3, and 4 featured intricate engravings and decoration. Style 4, for example, boasted Art Deco-style geometric shapes, surrounded by a chrysanthemum design credited to George Beauchamp, one of the original incorporators of National in 1928. Players today differ over whether they prefer the sharper, louder sound of the single-cone models or the softer, sweeter tone of the tri-cone guitars.
In contrast with Dobro guitars, Nationals have serial numbers that can be easily tied to a year of production. These numbers are generally found either on top of the headstock, on the body by the end of the tailpiece, or on the back of the bridge.
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615 Spotlight: Tim Menzies Explains Hiatus, Talks Gospel-Leaning New AlbumBillboard, August 27th
I played a guitar, came back and also played a resonator guitar on it. It was kind of a country-blues thing. I love it." Menzies is currently putting together a team to promote his music in the Gospel field, and is looking to start a tour of churches...Read more
Pups strut to support Rotary Dog ParkTBO.com, August 27th
of the Appalachian Mountains, sang and played the ukulele, banjo and guitar to early American tunes from her childhood years. Her partner in life and during her performance was fellow lawyer J. Steele Olmstead, strumming his Hawaiian resonator guitar...Read more
Former members of The Explorers Club join forces in HoneysmokeCharleston City Paper, August 27th
Honeysmoke doesn't claim to have created its own genre, but we think the local band's blend of bluesy guitars and breezy island instrumentation is pretty unique. The foursome uses lap steel, ukulele, harmonica, resonator guitar, upright bass, and the ...Read more
Musician reacquires instrument missing for 28 yearsBranson Tri-Lakes news, August 26th
Jackson was best known for playing the single inverted resonator lap guitar, a dobro. He also designed and custom made his own seven-string dobro he called a Shobro, which was a play on Shot and dobro. Allen and Jackson met when they were both ...Read more
GUITAR LEGENDS FEATURE IN NEW LIMITED EDITION BOOK ...SourceWire (press release), August 26th
Red Giant Publishing present Scarlet Page's highly anticipated limited edition large format book RESONATORS, providing a unique insight into some of the World's most respected guitarists from '60s Merseybeat through Rock 'n' Roll, Heavy Metal and Punk ...Read more
My Guitar: Chris Kirby's connection to the bluesCBC.ca, August 16th
Kirby bought the guitar in Halifax about three to four years ago on his way back from the East Coast Music Awards in P.E.I.. He bought the guitar after playing one note. Kirby's always wanted a resonator guitar because he's a fan of blues music. He...Read more
Slide And Fingerstyle Dobro LicksSonic State, August 10th
The company had this to say, "Resonator Guitar is a slide and fingerstyle loop library recorded with a brass-bodied resophonic acoustical guitar (sometimes referred to as a "Dobro"). With vocal-like slide playing and slick fretwork the library covers...Read more
New Gretsch GuitarsSonic State, August 5th
This round-neck resonator guitar has all the same features as the wildly popular G9201 Honey Dipper, with the additions of aged white fingerboard binding, screened headstock graphic and a weathered "Cactus Flower" finish. The vital feature of all...Read more