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.

About our sources | Got something to add?

▼ Expand to read the full article ▼

Best of the Web (“Hall of Fame”)

Vintage Guitars Info

Vintage Guitars Info

This great reference site features detailed sections for vintage guitar makers including Gibson, Fender, Martin, Gr… [read review or visit site]

Vintage Guitar and Bass

Vintage Guitar and Bass

Want to see all the old brochures and ads for your favorite vintage axe? Check out this great site, which showcases… [read review or visit site]



Clubs & Associations

Other Great Reference Sites

Recent News: Resonator Guitars

Source: Google News

Summer NAMM, 2014: In Photos
American Songwriter, July 21st

Chris Meikel of St. Louis Music plays a mahogany Alvarez AD66SB acoustic, one of many different instruments the company carries these days. Western swing guitar guru, Asleep at the Wheel founder, and really tall guy Ray Benson wails in the Eastman ...Read more

Parrotheads, Jimmy Buffett party down
Boston Globe, July 20th

delivered his most expressive vocal of the night with the soft, melancholic “He Went to Paris,” and “Lovely Cruise” closed the show with each band member exiting the stage one by one, finally leaving Buffett to finish the song alone with his...Read more

One of Johnny Winter's Final Interviews Goes Online
antiMUSIC.com, July 19th

Elmore James's "Can't Hold Out," Magic Sam's "Don't Want No Woman," Howlin' Wolf's "Killing Floor," Clarence "Gatemouth" Brown's "Okie Dokie Stomp" and Son House's "Death Letter" - the latter is Winter's second recorded resonator guitar performance ...Read more

London calling for nomadic musician
Stuff.co.nz, July 18th

It features the distinctive chords of his steel resonator guitar [made of melted down cutlery], and which lately have been amplified loud and clear in central Nelson. Ferretti is back home for a few weeks before heading with his partner and son to...Read more

Old Crow Medicine Show throws a barn-burning hoedown at the Uptown Theater
Kansas City Star (blog), July 18th

Songs are arranged with a variety of instruments: acoustic guitar, resonator guitar, fiddle, mandolin, pedal steel guitar, stand-up bass, drums, piano, keyboards, percussion, harmonica, plenty of banjo and lots of vocal harmonies. There were flurries...Read more

Exclusive Video: Barrett Anderson
Boston Herald, July 17th

The local blues ace and 2014 Boston Music Award winner came by to play tunes new and old on his sweet resonator guitar -- check out how this thing sings. We talked about the definiton of blues (loose) and the '90s Cambrage scene (awesome) and then he ...Read more

Slimantics: Losing an old friend
The Commercial Dispatch, July 17th

But my admiration for Winter is just as strong today as it was 45 years ago, when I stood in the mirror and played by first air guitar session. Naturally, I played "Good Morning Little School Girl," and when I broke into the guitar solos, my imaginary...Read more

Live: Music Picks July 17-23
Salt Lake City Weekly, July 16th

With his long, scraggly beard, Parr looks like a man out of time as he plays his resonator guitar or banjo, singing with true, heartfelt emotion. Parr's music will hit you on a very deep level; you don't have to be a blues fan for his a cappella take...Read more