Gear Review: National M-14T Thunderbox

Although known for its steel and brass instruments, National also offers many wood-bodied guitars, both tricone and single-cone biscuit bridge style. The M-14T Thunderbox is the most recent addition to National’s M series of single-cone mahogany resonators.

In the late 1920s, John Dopyera and George Beauchamp formed the National String Instrument Corporation to produce some of the earliest metal-bodied tricones—resonator guitars—which would be played by bluesmen like Tampa Red, Son House, and Booker “Bukka” White. The company, which ceased production in 1942, was revived by Don Young and McGregor Gaines in 1989, and the modern iteration continues to offer authentic versions of the original 1920s and ’30s designs, as well as modern adaptations that cater to everyone from blues players and folk acolytes to jazzers and beyond. 

Although known for its steel and brass instruments, National also offers many wood-bodied guitars, both tricone and single-cone biscuit bridge style. The M-14T Thunderbox is the most recent addition to National’s M series of single-cone mahogany resonators. Like the regular M-14, the Thunderbox has a 14th-fret neck junction, but the newer resonator has a deep body—four inches, compared to three inches on its predecessor—designed to give it a more powerful sound. Putting the Thunderbox through its paces, I found the guitar more than lives up to its name. 

A Formidable Guitar
When I took the M-14T out of the included hardshell case, with its prominent National Reso-phonic Guitars, Inc. stencil (you won’t be forgetting which guitar is in this case!), I was struck by how light it is compared to steel or brass versions—a pound or so less. Like many Nationals, the Thunderbox has unmistakably vintage-looking details: f-holes on the upper bout, three-on-a-plate tuners, and a slotted headstock. The shiny single-cone resonator stands out against the coffee-tinged hue of the body and the ebony fretboard. I imagine that in a dark room, the only visible parts of this guitar would be the mother-of-pearl fret markers and the resonator cover plate: a subdued but formidable presence.

Once you start playing the M-14T, however, you leave behind any pretense of subtlety. The Thunderbox is loud! Even with a soft touch, every note is pronounced, clear, and soaked in that National bell-like quality. But more than being loud, it’s punchy. The mahogany and slightly deeper body contribute to a more robust bass response, but the guitar is very well balanced. As I fingerpicked my way through Blind Blake’s “Diddie Wa Diddie,” I thoroughly enjoyed the distinction between the bass and treble registers. The bass is strong, but not like you would encounter with a non-resonator guitar. It’s never boomy—just rich and present—and the treble sparkles like razor-sharp needles without becoming piercing.

When strummed, the Thunderbox sounds bold—it would cut through easily in an ensemble. In fact, my one concern would be keeping the guitar under control in a band setting; the sheer force of volume could overwhelm other instruments. If you tend to pick closer to the bridge, you might find yourself moving toward the neck, just to back off from the guitar’s wallop of sound.


The Feel
I’ve found that the typical metal National comes across with a lot of gravity; it’s as if the instrument’s mass engenders a certain seriousness to the proceedings. You sit more upright and become very conscious of your posture when playing a National. But the light weight of the Thunderbox made it easy to leisurely plonk down on the couch and get inspired.

The guitar’s neck is subtly V-shaped and feels slightly chunky without being overly so. The action was low enough that I could maneuver my way up and down the neck quickly with single-string runs and fingerpicked blues tropes. A 1.825-inch nut translates into ample room between the strings for medium- to bigger-sized hands and nicely wide string spacing near the bridge. If you’re used to a narrower nut (1-11/16 or 1-3/4 inches, for example), the Thunderbox’s width might take some getting used to. 

There are usually tradeoffs between a 14-fret guitar and its 12-fret counterparts. The former obviously gives you more frets to work with, while the latter tends to offer greater bass response and an overall sweetness of tone. I didn’t have a 12-fret version for comparison—there isn’t one of this particular model—but again, the Thunderbox’s depth seems to offset any lost bass response, so you get the best of both worlds: plenty of bottom end and access to the higher frets. 

The Build and Setup
As with all the modern Nationals I’ve played, the Thunderbox is solidly built, with exquisite attention to detail. I could find no flaws in the workmanship, and cone rattle—common in cheaper instruments—was nonexistent. 

The action on a new National, which usually seems to be geared toward bottleneck slide, felt slightly lower on the Thunderbox. At first, I thought it might not be optimal for slide playing, but that was not at all the case. Whether played in standard or a slackened tuning like open G, the guitar sounded crisp and clear, with no audible buzzing or fretboard clanging.

The Bottom Line
One of the comments I read online about the Thunderbox was, “Do we really need a louder National?” That’s a good point. The originals were designed to compete with loud band instruments like horns and banjos, but modern amplification has removed the need for great volume from acoustic guitars. On the other hand, that loudness might in fact be a huge plus: If you play with a light touch but want that definitive National bark and projection, here’s a guitar that should make the job very easy and pleasurable.



BODY Laminated mahogany top and back; solid mahogany sides; 9.5″ single-cone biscuit bridge resonator; f-holes; satin Revolver or Denim Blue finish

NECK Solid mahogany; 25″ scale; slotted headstock; three-on-a-plate tuners; ebony fretboard; ebony nut; pearl dot fret inlays; 1.825″ nut width; 2.25″ string spacing at saddle; satin finish

EXTRAS John Pearse set 600L Phosphor Bronze strings (.012–.053); hardshell case; available left-handed



PRICE $3,060 street

This article originally appeared in the September/October 2019 issue of Acoustic Guitar magazine.

Top Gear 2019 - gear of the year
Our Editors included this product in our list of Top Gear for 2019. Click here for the complete list and links to each product review.

Pete Madsen
Pete Madsen

Pete Madsen is an acoustic blues, ragtime and slide guitarist from the San Francisco Bay Area. He's the author of Play the Blues Like..., an essential guide for playing fingerstyle blues in open tunings.

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