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Resonators Explained
... those "other" guitars
by Paul Kucharski
September, 2004

The first time I heard a resonator being played I knew immediately that it wasn't an "ordinary" acoustic guitar, but I wasn't quite sure what it was at the time either.   Because the player was also playing slide on it, it also was one of those religious experiences for me in that all I wanted to do after that was to figure out how to get "that sound".  That began for me what has so far been a 10 year relationship with resonators.   I had been playing slide since the 70's, but there was just something special about the nasal-sounding tone of a resonator that really intrigued me.   I think it's that piercing pure tonal quality that resonators are capable of that make playing slide music on them so much more satisfying.  

National's new Reso-rocket

National Reso-rocket

The first thing I discovered when I began investigating these bizarre instruments was that there were a lot of different models and design differences out there.  Just wanting one wasn't going to do it.  Like acoustic guitars, every variation in instrument design yielded a different tone and I discovered I needed to learn more before I knew how to spend my money.  Eventually I came to own a half-dozen of these over the years.

If you've been wanting to delve into resonators and haven't done so because you didn't know how to make the tradeoffs, I hope to provide enough of an overview to help you decide what resonator might best suite your needs.  They certainly do look different, but they all sound just as different as they look.  And just like guitars, knowing the differences are important to selecting the one that will give you the sound you want. 

What I won't do is delve into the history of these instruments.  There are plenty of other sources for this information and knowing it doesn't help make any decisions unless you're thinking about a vintage instrument.  So let's get started.

First Some Terminology
Before we delve too far into the makes, models and differences of the various resonators, we first should clear up some terminology associated with these things.  A common point of confusion for many is the appropriate word to use for this category of instrument.  I've used the term resonator, but some call them dobros, while others only refer to square-neck resonators as dobros .  While dobro has historically been used in reference to these instruments, it also introduces confusion because "Dobro™" is also a trademark name for a family of resonators made by the Gibson company.   The name is derived from the inventors of the instrument; the Dopyera Brothers (DoBro) (I know, I said I wouldn't talk about the history... but just this little bit).  They sold a line of these instruments under that name for many years and Gibson acquired the rights to the name when they began producing their own line.  To avoid confusion with the brand, I only use the word Dobro when referring to the brand name.  

So for purposes of this article I offer the following definition:

Resonator: Guitar with one or more metal resonator discs mounted inside the body.

Resonator Types
Squareneck resonator
There are two fundamentally different types of resonators based on the type of guitar neck they have: square-necks and round-necks.  These differences are significant because it changes the entire way in which you play them.  A square-neck resonator is laid flat on your lap.  These have a special nut that raises the strings high above the fretboard and are typically played with a special slide generically called a Stevens Steel.  You can see in the picture on the right that the neck is very thick and squared off to make a flat and rigid support.  This type of instrument is what you see Jerry Douglas, Rob Ickes or Mike Auldridge play.  This is the type most commonly used in bluegrass music.

The round-neck type on the other hand is held and played just like a regular guitar.  The neck profile and nut is basically an ordinary guitar neck.  If your goal is to play bottleneck slide the round-neck type is what you should be looking for.  If your goal is to play lap slide like Jerry Douglas, you want to be looking for a square-neck model.  In general, the round-neck type is the more versatile of the two.  There are special nut converters for example that raise up the strings to convert a round-neck into a lap-slide configuration.  

Resonator Designs

Within these two primary categories, there are 3 primary designs based on the number of cones and the design of the bridge.  They are the single-cone biscuit-bridge, single-cone spider-bridge, and tri-cone.  In all these designs, the aluminum cones act very much like the speakers in your stereo.  The strings make contact with the biscuit-bridge, spider-bridge, or T-bridge and these bridges transfer the vibration to the cones.  The cones in turn vibrate to move the air volume inside the guitar and out the sound holes.  

Biscuit-Bridge Single-cone Design

single-cone biscuit bridge
Photo Courtesy of 
National Instruments

DonMo Wood Body Single ConeThe simplest of the designs is the biscuit-bridge single-cone.  The biscuit-bridge cone looks basically like an inverted speaker cone.  The biscuit bridge gets its name from the little wood disc (generally made with some solid hardwood) in the center of the cone.   The saddle is also generally made of wood and sits in a slot in the biscuit.  The cone rests on a small ridge on the bottom of a well built into the body.  Because there is only one cone and the string vibration drives a single point on the cone, these resonators tend to generate a stronger fundamental tone with less complexity or overtones.   You will find this cone design used in both metal body (like the ResoRocket above) and wood body models (like the DonMo on the right).  The metal-body biscuit-bridge resonators were highly favored by delta blues players because of their loud metallic tone.  When used in a wood body, the tone has less crispness and a bit less brittle, but still has a strong fundamental tone.  Listen to some mp3 sound samples.

There is a wide variety of builders and price ranges for this style of resonator.  At the high-end, National is the most well known brand with a wide variety of models.  If you can afford a National, you can't go wrong with any of their models.  There is also custom builders like Australian builder Don Morrison (DonMo) who is the builder of the instruments I use.  But if you are just beginning to explore these instruments and don't want to invest a lot in an instrument to start with, there are a number of imported alternatives like the Dean Metal Body acoustic-electric, Dean CE acoustic-electric, Regal RC2 Duolian, Regal RC1 Polychrome Duolian, or the Epiphone Biscuit

Tri-cone Design

tricone w/T-bridge
Photo Courtesy of 
National Instruments

National Style 1 TriconeThe 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 sound of the vibrating strings get distributed to the three cones and the vibration of these cones combine/interact within the body of the resonator to create what can be described as a more distributed complex sound.

There is a less immediate attack when the strings are plucked or the slide is applied.   The more complex tone, the existence of more overtones, and a generally greater sustain make the Tri-cone a favorite among slide players; particularly in the style of Robert Johnson.  

Wood versus Metal in the Tri-cone family also modifies the overall tone by taking out some of that brittle metallic tone.  Many blues players want that metallic brittleness however, so it all comes down to preferences.

There are very few builders who make a wood body Tri-cone currently.  DonMo is one who does, so you can get an idea of effect a wood body has on the Tri-cone design.

There is a wide variety of builders and price ranges for Tri-cone resonators.  In the high-end range of the market, National is the dominant name.  But builders like DonMo and some European companies build fine instruments as well.  For a beginner wishing to explore a Tri-cone but don't want to spend a lot, Regal and Johnson also offer Tri-cone models.  A Regal model like the Regal RC-51 Tricone, or the Regal RC-58 are very reasonably priced.

Spider-bridge Single-cone Design

Photo Courtesy of 
National Instruments

Paul Beard R-Model Square NeckThe single-cone spider-bridge design gets its name from the spider-like look of the bridge.  The cone itself has a W-shape to it and the spider bridge contacts the cone in both the center and along the edges.  So with this design, string vibration gets distributed to numerous points around the cone.  Also, the spider cone is more like a typical speaker in that the spider cone has its concavity reversed so more of the sound is driven out directly rather than into the body.  This change makes a dramatic difference on the tonal properties of these instruments.     In addition, often these cones sit in special sound wells that modifies the tonal character even further.  The best term I can think of to describe it is a more "nasal" tone.

Typical sound wellThe spider-bridge design is the type most often used in square-neck models and is what provides that characteristic bluegrass resonator tone you hear from players like Jerry Douglas.  This type is also most often built with a wood body rather than metal body.  It can be found in round-neck models as well. 

There a LOT of builders and price ranges for spider-bridge resonators; both square neck and round neck.   It is a very popular design in both the high-end and low-end.  The majority of the high-end builders specialize in the square neck models but generally offer them in round necks as well.  Names like National, Crafters of Tennessee,  Gibson's Dobro Brand and Paul Beard (which is what I have) all make fine square neck models; but a complete list of builders would be much larger.  

For beginners there are a number of imported alternatives like the Regal Black Lightning and others like the Dobro Hound Dog. Paul Beard now offers a lower priced squareneck under the Gold Tone label ( Goldtone Signature Series). What's great about the Goldtone Series is that it uses Beard components for the critical parts.

In the round neck variety, there are models in the Dobro Hound Dog as well as the Fender FR50CE  or Fender FR-50 that are very cost effective starter instruments.  Beard also offers his Goldtone Signature Series model in a round neck.

Other General Considerations

The body of resonators actually play a much smaller role in the overall sound of these instrument compared to a regular acoustic guitar.  On a regular acoustic, the top wood of the guitar is the predominant sound generator.  The better the wood and the more time spent on optimizing the tap tone, the better the sound.  On a resonator, the cone generates the vast majority of the sound.  You could say that 80% of the tone's in the cone.  In fact, the stiffer the body of a resonator the better.   This is why resonator builders who make wood body models typically use thick laminates instead of solid wood.   Many builders and retailers will tell you there is no strong tonal benefit to justify the extra expense of solid wood.  The only significant justification for the expense of solid wood on a resonator is its inherent beauty.

Also, the cones used in many of the imports vary quite a bit in quality and many who buy these often will eventually purchase a replacement cone/s from places like Paul Beard's Resophonic Outfitters.  Because so much of the tone generated by resonators comes from the cone, the improvement can be quite dramatic.   It's beyond the scope of this article to delve into this process, but you should at least note that if you do buy an import, there is at least one relatively simple thing you can do to them to improve their sound when you're ready to take that step.

Now that you know the differences of the various resonator designs, there are some other factors to also think about.  One thing you may not notice right away when shopping for a round neck resonator is that the majority of these are made with 12 frets clear of the body.  Many acoustic guitars are built with 14-frets clear.  The first time you try to bar the 12 fret with your slide, you'll discover the limitation this can have.  So another choice you have is to seek out resonators that are either built with 14 frets clear or have a cutaway.  For example, National now offers two models with cutaways: the new ResoRocket metal body single-cone and the Radiotone wood body single-cone.  DonMo offers a cutaway in all his models if you want one; including tri-cone models. 

There are a couple of variations that you might come across in resonators that I should make note of.  One common variation is a Baritone model.  These are made with necks that are a couple inches longer (generally 27") to allow them to be tuned down 2-3 whole steps.  This gives the instrument a very deep growling low end.   I use a baritone to play songs that better fit my vocal range in the key of C for example.  

The last variation I want to mention is models that feature more than 6 strings.  Some custom builders like Paul Beard offer square neck models with 7 or 8 strings.  Most players have enough trouble with 6-strings, much less 7 or 8, but there are some who find more is better.

That about wraps it up.  Resonators are so unique in the kind of tones you can produce that even if you already have an acoustic guitar, a resonator offers such a completely different palette of sounds that it is pretty easy to justify having both.  And the sound of each resonator design itself offers a wide tonal spectrum to explore.   So it just goes to are like potato can't have just one!