the JD custom

This is the text I sent to Bob Shaw, for his book "Hand Made, Hand Played" :


"Hi Bob,

Jeff basically gave me carte blanche - the wilder the better, he said & kept encouraging me to push the envelope.  I'll try to explain the thoughts leading to the design and the construction - bear with me if it's a little confusing at times -

We quickly settled on a "Novax" fanned frets fretboard.  If I remember correctly the scale is 24"/26".  That was the easy part.

I wanted to make a guitar which would offer some unusual sound-shaping options, derived from various string-anchoring techniques. I wanted to try an idea I'd had for a while, which was to create a "reverse" spider, vaguely reminiscent of a Resonator guitar's spider.  Made of Walnut burl, it sits on top of the soundboard and supports the bridge/saddles floating above the soundboard sandwiched between the spider and the carved-out back of the guitar.  The strings pull up vertically on the soundboard, rather than laterally, as in a conventional design.

The guitar body consists of a old-growth flame Mahogany/Rosewood back, largely carved out, with a Spruce soundboard glued over it to create a hollow-body type of guitar body.  The "spider" is glued on top, creating the sandwich with the soundboard in the middle.  The saddles are anchored to the spider proper, but they rest on a small plate inserted into a recess at the top of the spider.  In this design the strings come straight up from below, in the manner of a "through-body" design, through holes in the bridge plate which supports the saddles and then pass over the saddles to the nut.  The spider, like an arched roof structure, distributes the downward pressure towards the rim.  

The idea is that there are various options to create different tonal responses: 
There are the two different anchoring points for the strings and several bridgeplates made of various materials which support the saddles. 

A) The strings can be fed through a plate which inserts into a recess in the back of the guitar and is fitted with ferrules.  Then they pass through the  ferrules set into a bridge plate glued to the underside of the soundboard and through holes in the bridgeplate to reach the saddles.  Since it's a straight line up from the ferrules in the back to the saddles, the soundboard is not under load.  The string pressure is carried by the back, thus involving the "outer shell" of the instrument.

B) The ferrule plate in the back is removed and the strings fed through the opening and anchored via the ferrules in the bridge glued to the back of the soundboard.  In this variation the soundboard is subjected to the string tension while the back is load free.  The string vibration will excite the sonudboard directly.

(this made me a bit nervous as to how the bracing of the soundboard would hold up, since the vertical pull of the strings is quite a bit more powerful than the conventional mode of construction)

C) The bridgeplate supporting the saddles can be swapped out, I supplied Jeff with a few made of different materials (woods, brass etc.)  Since the string pressure on the saddle is straight down, pressing it tight to the plate, the material of the plate has a direct impact on the sound.

These options can be mixed - I liked to string the 3 bass strings through the back, the 3 high strings through the soundboard using the Rosewood bridgeplate as saddle support.  However, since it is a bit involved to change these options, I did not really get to explore them in depth.  Maybe Jeff has a few things to say about that...

The neck is mounted with a lateral dovetail type joint onto the body and secured with three bolts. The neck is made of Mahogany (same as body) with an Ebony fingerboard.  The headstock is carved from aluminum and bolted to the neck. The tuners are Steinberger banjo-style tuners.

The pickups are older John Birch units, an English luthier who worked for Tommi Iommi and others, developing custom pickups for them.  I liked their rustic, handmade flair.  They are rather rare and for years I saved them for a special project.  The bridge unit is mounted directly into the spider, the neck unit is supported by a sculpted aluminum piece which floats over the body of the guitar and provides a strap attachment on the upper horn and on the other end supports the electronics floating above the guitar body - somewhat like an archtop type of floating pickup/control unit.

I machined the saddles from Mokume, which consists of thin layers of various metals folded and forged together, creating raindrop patterns much like a Damascus blade.  The fretboard is Ebony, flanked by Flame Maple, with side dots made of colored bone.  The are translucent and when they are lit from above or the front, they light up softly.  The body is finished in Nitrocellulose lacquer.

That's about it I think -

Is it a successful design?  Largely I think so - I liked the playability and the way it would feed back harmonically and the various electric tones it provided.  I was a bit disappointed with the acoustic tones - a bit banjoish/resonatorish - although it's not surprising - after all the design has some parallels to resonator design. 

Anyway, if something isn't clear or you have more questions, please let me know -

Michael Spalt"