a 12-string acoustic guitar with two added sub-basses (14-string guitar)

Built by Fred Carlson for Marc Dorsa, Autumn, 2000


Marc Dorsa is one of my favorite guitarists. He plays his beautiful, original compositions with passion, precision and delicacy, and I felt honored and delighted when he approached me about the possibility of building him a 12-string guitar to go with the 18-string Sympitar (Zephyr) that I'd built for him in 1996. As with Zephyr, Marc had a very clear image of the kind of sound he wanted. Part of that sound included adding two additional bass strings, running parallel to the main strings off the bass side of the fingerboard, something like the sub-basses of a harp-guitar.

When I built Marc his Sympitar, he first presented me with a drawing of the instrument as he envisioned it, which became the basis for the instrument's design. With Kali, I was given a few design criteria to work with: 12 main strings, 2 sub-bass tuned to D and G (the D below the low E of a bass guitar, the G a fourth above that D), possibly a sound-hole positioned off-center toward the bass side, and a bridge position, relative to body size and shape, that would feel similar to Zephyr. Beyond that I was encouraged to follow my own intuition in designing the sculpture of the instrument. My recollection is that the design for the body flowed out quite easily and naturally. The cutaway became a wave that got transferred to the design decorating the access door in the instrument's back. The angled, oval, off-center sound-hole developed a strong relationship with the outline of the upper bout on that side. The sweeping curves of the bridge directed the movement or flow of lines like gesturing wings.

The big trick was the peghead extension that holds those additional sub-bass strings. I knew the strings needed a long vibrating length, at least 32 inches, to get a reasonable sound from those low pitches. I wanted the sub-bass strings to stay pretty close to the same plane as the main strings, which meant having an extension of the top of the peghead that not only curved off to the bass side, but also was elevated, built up to account for the amount that the peghead angles back from the plane of the fingerboard. This elevated extension had to support quite a lot of tension, be as light as possible for physical balance and comfort, and somehow make sense as a part of the whole sculpture. I ended up building a multi-pieced tower that is carved and shaped to grow organically out of a cleft in the peghead veneers. The multiple pieces are laminated to orient the wood's grain for maximum strength. Initially we used Schaller nylon-bodied 12-string tuners for all the strings, for weight reduction. These turned out to be inadequate for the sub-bass strings; it seems the nylon gear housing allows more play under tension than a typical cast metal-bodied Schaller tuner has. The lowest string began to strip the gears on its tuner. We replaced both sub-bass tuners with metal-bodied Schallers and have had no such problems since.

Another difficulty I had was in gauging how thick to leave the neck. The walnut was reinforced with 2 epoxy-graphite bars running the full length of the neck, on either side of an adjustable truss rod. This seemed like it should be adequate, but I was concerned about weakening the neck by removing too much wood when carving it. Consequently, Kali started life with a very hefty hunk of a neck. Marc and I agreed that we would let her settle in for a while, and see how the neck fared; if it didn't show signs of being too stressed, I'd consider removing more wood. It didn't take long for Marc to realize that the size of the neck was really cramping his playing style (I imagine literally cramping his hand as well). It also became clear that the neck was not in any danger and wood could be safely removed. I finally made some time in my schedule to re-carve the neck, making a tremendous improvement in playability.

To support the tension of the strings, Kali was braced with a modified X-pattern of struts. Where the legs of the X pass under the wings of the bridge two sets of fanned struts extend toward the perimeter of the top and are locked into the X with capping pieces of spruce. A floating transverse brace ties the two upper legs of the X and one of the treble-side fan struts together. This adds needed stability to the crucial area where string tension pulling up on the bridge tends to dish the top inward, and does so without adding more mass or glue directly to the top itself. Several small redwood struts are used for lightweight tensioning of specific areas and there is a redwood pad underneath the thin ebony bridge plate. The other struts are all Sitka spruce. The top is joined to the sides with individual spruce blocks (tentallones or dientes) and a kerfed lining serves that purpose for the back-to-side joining. Sides are slotted into the neck-block Spanish-style, allowing the cutaway to flow into the shaping of the walnut neck-heel.