Why Carbon Fiber?

 

This blog post is long overdue.  

Many people have asked about my carbon fiber instruments.  Some of the questions relate to the actual instruments; some questions are about carbon fiber as a tonal material.  I'll attempt to address both questions here.

THE INSTRUMENTS

Most of my performing (used on tours and in recording sessions) instruments are carbon fiber, and made by Emerald Guitars in Ireland.   My carbon fiber instruments could not exist in wood.  There are too many strings exerting greater forces than could be countered in wood.  I've spoken with two of the other luthiers that make wood instruments for me about these instruments.  In fact, prior to the creation of the 30-string Contra-Alto guitar, I had worked with one famous luthier who has made a few instruments for me, to try to make this instrument work in wood.  This concept was discussed for a few years.  But by the time an acoustic wood instrument was braced for 30 strings, it would have little to no resonance.  Additionally, all those forces would slowly destroy the instrument over time.   My Emerald carbon fiber instruments have come to be known as the Emerald Guitars Kevin Kastning Signature Series.  With the possible exception of the 15-string Extended Classical guitar, none of these instruments could exist in wood, and were only possible using carbon fiber.

I think some  may see carbon fiber as a cheaper alternative to wood instruments.  On the contrary, carbon fiber is more expensive than nearly any tonewood.  The decision for carbon fiber has nothing to do with cost, as I'll explain.

TONAL RESULTS

Prior to discovering carbon fiber instruments, I was a total acoustic purist.  Well, to be honest, I still am, but that purism now embraces carbon fiber along with tonewoods.

I've worked with Santa Cruz Guitars and Daniel Roberts Stringworks in designing wood instruments.  I've learned about the different tonal properties of tonewoods.  It's an endlessly fascinating topic.  When designing an instrument in wood, you can shape its voice and tonal response by which tonewoods are used for which parts in the instrument.  Tonewood selection enables you to shape and color an instrument's voice to be dark, bright, mellow, and so forth.  However, because tonewood is a natural and organic material, you don't know how the instrument is really going to sound until it's finished.  Shaping the voice with tonewood is an approximation, not an absolute.  Additionally, wood instruments go through a process called opening up that requires several years.  In reality, you won't really and fully know how that instrument is going to sound for years after it is completed.

In the world of carbon fiber instruments, all that uncertainly goes away.  Carbon fiber, being a manufactured material, is incredibly consistent and uniform.  There are no surprises; either after the instrument is completed, or years later after it has opened up.  What you hear in a carbon fiber instrument is the sound of the string itself.  The carbon fiber does not color the tone or voice of the instrument.  It's the ultimate in acoustic purity.  You can shape the color and voice of the instrument by using various string winding compounds; for example, in bronze-wound strings you'll really hear the difference between 80/20 compounds and 92/8 compounds.  This provides some additional choices in coloration that do not exist to this extent on wood instruments.  You can also color the voice by how you play; with your fingers, your attack, your touch, vibrato, and infinitely more.  Of course that's also true with wood instruments, but becomes far more apparent and tangible on carbon fiber instruments.

Then there's the matter of balance.  Balance in this case is defined as how well and evenly the instrument speaks or responds in all registers.  It's very difficult to achieve a well-balanced wood instrument.  It's not that it can't be done; it can.  But there is no comparison between the balance in well-balanced tonewood instruments and the perfect balance in a carbon fiber instrument.  Carbon fiber instruments speak with perfect balance across all registers.  This is important to me, as my instruments cover some very wide ranges across multiple registers, and I'm utilizing the entire range of each instrument.  Each instrument speaks and responds with perfect balance in every register.  That's miraculous to me.

Possibly my favorite tonal quality in carbon fiber instruments is the responsiveness; both tonally and in dynamics.  Carbon fiber speaks at the slightest touch.  There are times wherein it feels as if it's reading my mind.  It is so alive and responsive that there are techniques, both singe- and double-handed, I've developed on carbon fiber instruments that don't work on wood instruments.  To say that carbon fiber instruments have expanded what I can do, both in technique and expression, is an understatement.  Now when I pick up a wood instrument, it's full of limitations.  However, responsiveness is a two-sided coin: while carbon fiber instruments are indeed incredibly responsive, that response is also going to greatly magnify any deficiencies in your technique.  Any mistakes, any kind of misfretted notes, are going to speak loudly and become far more obvious than on wood instruments.  Moving to carbon fiber has forced me to further evolve my technique and touch.  One quick example of this is the physical location of fretting the string.  One wood guitars, the accepted technique is just behind the fret.  On carbon fiber, that's not always enough.  I've found that I need to fret the string almost on top of the fret; not quite, but close.  The additional investment in technique was well worth it.

THE MATERIAL

I won't go into the scientific definition or background on carbon fiber; you can read about that here.  I will say that carbon fiber has an extremely high strength-to-weight ratio, is stronger than steel, and is very stiff.  Luthiers of wood instruments are constantly seeking the stiffest tonewood possible for acoustic guitar tops, but carbon fiber is far stiffer than even the stiffest tonewood.  This stiffness adds to its wonderful acoustic properties.  

Carbon fiber is nearly impervious to temperature and humidity, two of the leading causes of damage to acoustic wood instruments.  The action never fluctuates from summer to winter.  Winter humidification is not required.  The tonal response of the instrument is consistent, regardless of seasons, humidity, or temperature.  With wood instruments, I have to keep a humidifier running throughout the winter months.  Truss rods require adjusting in winter, and then again in summer.  I play with a very low action at slightly above 1/32" on the treble side, and about 2/32" on the bass side.  It's difficult to maintain that kind of action on an acoustic wood instrument; any change in the neck angle or bridge due to humidity or lack of humidity will negatively impact the action, requiring a truss rod adjustment.  With carbon fiber instruments, I can adjust the truss rod once, and that's it.  I have carbon fiber instruments that have not had a truss rod adjustment in years.  In fact, there are only two instances wherein truss rod adjustments are required on carbon fiber instruments: when the instrument first arrives to adjust the action exactly where I want it, and later if I radically change string gauges enough to impact the truss rod.  For the latter scenario, I believe that has only occurred once (on the 36-string).  

CONCLUSION

Carbon fiber stringed instruments are also making inroads in the world of classical music.  Carbon fiber violin-family instruments from Luis and Clark are showing up more and more in orchestras, and in the hands of soloists such as Yo-Yo Ma.

I love carbon fiber instruments.  I love everything about them: the stability, the limitlessness of the experimental instruments that can be created from carbon fiber, the incredible responsiveness, and the tonal properties, balance, and voicing.  Like everything in the realm of instrument choice, it's always very personal and it may not be for everyone.  However, if you're an acoustic guitarist, either steel or nylon string, you may well owe it to yourself to try a carbon fiber instrument.  Carbon fiber instruments have made one of the biggest impacts in my playing and in fact, in my life, over just about anything else of which I can remember.

To put it another way: if the 36-string could exist in wood, I'd still prefer it in carbon fiber.

I originally moved to carbon fiber due to requirements for my multi-string instruments, but now after living with carbon fiber instruments for 10 years, I almost always prefer them over wood instruments.

-kk