I have been interested in building an electric cello for many years. I have a brother who is a professional cellist and my father was a professional violist, so I have been around bowed strings all my life. I hadn't taken up playing one until I was in college in the 70's, and then it was the bass viola da gamba, which I play to this day. So, not being a cellist myself, I approached the project as a guitarist/gamba player. I thought about putting frets on the thing and making a sort of arpeggione (essentially a bowed guitar), but I decided to stick to basics for this first foray into electric instruments.

Models/Design

I looked at a lot of electric cellos to see how others had done it. I wasn't interested in reinventing the wheel. I came across the early Jensen models and was impressed with his minimalist approach. I had a brief opportunity to look at and play a Jensen and decided this was a good concept to start with (famous last words: "Hey, I can do that!").

To get an accurate geometry, I made a full-size drawing using angles and measurements from two reference works: Making Stringed Instruments, by George Buchanan, and Useful measurements for Violin Makers, by Henry A. Strobel. Since the neck angle on a traditional cello results in the lower end of the fingerboard hanging out in mid-air, the balance on my cello moves the center of gravity quite a bit forward. The alternative would have been to have an angle in the middle of my body, which I didn't think would help that much and would look odd. Besides, Jensen didn't do that so it must be ok, right?

I used an overhead projector to blow up drawings from the books mentioned above to full size. I then superimposed the solid body profile on the drawings to make the final plan.

Click images for larger

Fingerboard

One of the first decisions I made was to make my own fingerboard using a gorgeous piece of rosewood I had been saving. This decision turned out to have broad implications for the whole project. Traditional cello fingerboards actually have a  fairly complex geometry. There is a flat part under the C (lowest) string that is helpful for ergonomic reasons.  There is also sort of scoop along the length of the board that allows the lower pitches to vibrate freely without buzzing, but rises up again towards the high end to keep the strings from being too high off the fingerboard. Fitting a fingerboard to an instrument is a highly skilled task for the luthier and I didn't want to work that hard. So my fingerboard is slightly wider than standard, has an even curve along its latitude and is perfectly straight along the longitude. This is very similar to a viola da gamba fingerboard, so I was pretty comfortable with it, though it feels odd to a traditional cellist.

If I was making the instrument for a cellist, I would have bought a pre-made ebony cello fingerboard. In fact, I did buy a Moses graphite cello fingerboard for this project (I paid very little for it at the time because they were just starting to make them and I was a dealer). When I got the Moses, I realized that it was just a blank that would still need significant work to get it to final shape. I didn't really want to work in this material because it is, frankly, pretty unpleasant and makes black powdery residue everywhere (imagine running a giant pencil lead through a blender with the lid off). Just the idea of cleaning up my tools and shop was enough to dissuade me, much less breathing the stuff. On the other hand, ebony is also pretty awful to work. It can be splintery and the dust smells bad. All in all the rosewood option was chosen for its esthetic and working qualities in the face of these not very inviting alternatives. Rosewood is wonderful to work with, not the least because of its lovely smell.

Body

I made the essential body of a single piece of hard maple. This material is used for violin-family bodies because it is very tough, resilient, works well and finishes out smoothly. Its density is good for solid body electric instruments because it is not resonant and so avoids problems like dead pitches (wolf tones) and feedback under high amplification.

The first thing I did was to make a full-size mockup using cheap pine lumber. I wanted to check the geometry and balance, and make sure I had enough of an angle from the nut to the tuners. If I were to need a steeper angle, I would need to redesign the headstock or use a different piece of maple. I really wanted it to fit the board I had and the mockup showed I was within tolerances.

I was concerned, probably for no good reason, about the neck bending under tension. I used the table saw to rout out a groove down the middle of the neck into which I epoxied a 3/4" x 1/8" steel bar. The steel-epoxy matrix along with the hard maple and the rosewood fingerboard was probably overkill and unnecessary.

I initially included a pronounced thumb stop on the back to indicate where the heel of the neck would be on a normal cello. After trying it out it just seemed to be in the way, so I removed most of it and re-contoured the whole back side to to make it a smoother transition from the neck to the body and tail. These pictures were taken of the original profile.

One problem I had was whether to add an extension on the back of the neck that takes the place of the heel of the neck - a part that would normally touch the player's chest on a real cello. Jensen used a detachable piece, so I did something similar, but easier to manufacture. I inset a brass female screw thread into the back and simply used a threaded steel rod with a maple drawer pull attached. This piece could be unscrewed easily for storage.

The Support Structure

For the support structure I used standard 5/16" steel rod stock from the hardware store. The main vertical rod is a bit springy under the weight of the instrument. The various components are made of maple with standard T-nuts and thumb screws, which I covered in nice wooden handles.

The main support block needed to have the thumb screw pushing against the rod. In order to make this work without damaging the wood, I cut the block in half and embedded a T-nut inside so that the screw was pulling against the wood rather than pushing. I then glued the block back together with epoxy. In the lower end of the block is the endpin that holds the tailpiece (both from used ebony cello parts). The block is fastened to the back using a couple of dowels, and a wood screw towards the top end. It is not glued in place. When I first strung it up there seemed to be a lot of torque wanting to pull the block off, which is why I added the screw.

The lower bouts are simply made of maple and a steel rod mounted similarly to the main support rod. I made this part somewhat narrower than a standard cello body because it just didn't feel right. Placement of all the other component parts is adjustable.

Tuning heads

I was able to purchase a set of left-handed Grover bass tuners. The guitar store where I bought them actually had them left over from selling a set of right-handed tuners made from two sets of 2 by 2's. They are gold plated and work like a charm.

Bridge and pickup

I cut the body just below the bridge in order to provide a sufficient downbearing angle on the bridge. The bridge itself is maple and fairly simple in design. It has a slot in each side and a rectangular hole in the middle. The Fishman cello piezo could be wedged into any of these spaces. I set the bridge in a slot in the body on a thin piece of spruce to provide a little springiness.

The Fishman was the most expensive single part of the project. Since the piezo is more responsive to the treble end, I ended up wedging it under the low C string to help balance the sound level. The wire runs to a jack held in a holder that is velcroed to the side of the support block.

Sound and response

Ten years later I still haven't decided if this was a successful project. I rarely play it because I'm not thrilled with the sound. It's very edgy from the piezo, but this is true of any piezo transducer. I use a fair amount of EQ to balance the tone, but it still doesn't sound right to me. The overall feel of the instrument is kind of top heavy and unstable. There is too much wobble in the support rod -- this might be fixed by using a stiffer type of steel or perhaps a square shaft.

I keep the instrument handy, ready to play whenever the mood strikes, but that's still pretty rare. At one point I tried to modify it into an electric arpeggione by adding a magnetic pickup and two more strings. Big mistake. There wasn't room on the fingerboard for the extra strings and magnetic pickups don't really work right with bowed strings (I knew this, but I had to try it anyway). So I re-converted it back to a cello, but the aesthetic damage to the body is a bit nasty.