The EC is a set of design elements which allow a guitar neck to be attached to the instrument body in a way that substantially reduces the interference of the heel with the player's hand. The primary goal of the EC design is to remove the heel from beneath the portion of the neck which lies on or near the body of the instrument, thereby allowing a guitar player to maintain proper hand position, with the thumb behind the neck. A secondary goal is to achieve this unprecedented access while improving the structural stability and the tone of the instrument.
The EC is most commonly configured so that the heel of the neck extends outward from the bass side of the neck, instead of below the neck as on conventional designs. This position allows a guitar with a cutaway to have a "pocket" under the heel end of the neck for the palm and thumb of the players fretting hand, thereby "extending the cutaway".
The first benefit of the EC design is that as a player you will have freer and more useful access to the upper third of your fretboard. You will be able to maintain proper hand position anywhere on the fretboard. When you first put your hands on the EC neck, it becomes immediately apparent how conditioned you've become to changing your hand position when playing the higher notes on your instrument. It takes a few weeks to adjust to the new-found freedom of the EC design.
Standard bolt-on, solid-body guitars begin to restrict playing facility at around the octave. Many guitar players that play in bands with other instruments, such as keyboards and wind instruments, discover how low the range of the guitar actually is (in fact, it sounds an octave below where written), and frequently find themselves in the upper portions of the fretboard. Being able to use this portion of the fretboard more fully will allow you to be more musical, without having to think "can I do this up there?".
In addition to the increased ease with which you can play the guitar, many players note increased warmth of tone on instruments that have an EC neck. Whether or not you play above the octave, anyone will be happy to have improved tone and stability on their instrument.
The EC can be constructed on any type of acoustic or electric guitar using all of the standard neck joint formats; bolt-on, glued-on, through-body or Spanish heel. The most widely used format is the bolt-on Extended Cutaway on the solid-body electric guitar.
With conventional heel construction, the structural elements of the neck extend below the neck. This positioning, while simple and very obvious from the engineering standpoint, puts the structural elements of the neck joints precisely in the way of the player. The conventional structure also has the property of creating a very high degree of stiffness in the neck in one plane (up and down) and a very low degree of stiffness in another plane (side to side), which has somewhat of a dampening effect on tonal production.
The EC neck joint moves the structural elements of the heel joint off to the side of the neck, removing any impediment to proper hand position. This structural realignment changes the stiffness of the neck joint in a way that enhances tone.
Another benefit of the EC is improved structural stability. On conventional guitars where a portion of the fretboard lies over the body of the instrument, it is common to have fretboard linearity problems show up as an instrument ages. This is because the design of the truss rod and its action is such that the truss rod cannot maintain straightness over the entire length of the fretboard, especially where portions of the fretboard extend beyond the neck. With the EC design the entire fretboard is supported by the neck and truss rod and is able to maintain its linearity over time.
The bolt-on version of the EC neck joint consists of a neck whose heel is arcuate or circular in shape and has a tenon or protrusion which extends outward from the bass side of the neck, which from the front of the guitar looks somewhat like a shark fin. The end of the neck therefore describes a portion of a circle which mates in a circular shaped neck pocket in the body. The neck and body are then bolted together with a half-moon shaped neck plate and five neck bolts. The resulting joint is extremely strong and extremely stable owing to increased mating surface area and leverage, the five neck bolts, and the circular shape of the connection. The shape formed by the end of the neck describes a portion of a circle, the center of which is located outside the treble edge of the neck. When this neck and circular heel is mated into the guitar body, the string tension serves to rotate the heel into a locked position and prevents any instability or extraneous motion from occurring in the joint. The five-bolt design of the EC neck joint is extremely stable and will not move from side to side as is
common with the older 4-bolt design. Because of this, energy transmission from the neck back into the body is improved and the tone of the guitar is noticeably warmed up.
The conventional four-bolt design is extremely stiff with respect to one direction (front to back), and extremely loose with respect to the side-to-side direction. When a guitar string is plucked, the energy produced by that string is radial in nature and with 4-bolt designs the energy transmitted by the string into the neck is only partially passed on from the neck to the body, depending on the direction of energy.
The Extended Cutaway neck design is somewhat less stiff with respect to the front to back motion and considerably more stiff with respect to side to side motion. This more balanced structure passes more of the string's energy into the guitar body thereby improving tone noticeably.
The development of the Extended Cutaway began in the early eighties. Stephen Davies was a luthier and guitar player with a degree in music and a background in classical and jazz guitar styles. One night while playing with a jazz band at a blues dive he decided to transpose a bridge to a song by Theloneous Monk up an octave. He blew the part and later that evening, after being given a hard time by the other band members, asked the question "Why did that happen?" With years of classical guitar training, it occurred to him the obvious problem was improper hand position caused by the thumb being forced out of position by the heel on his guitar. Realizing the obvious solution was to remove the heel of the guitar, Davies set about working on structural designs that would accomplish this without compromising the integrity of the instrument. Within a few years, initial prototypes were built on acoustic steel-string guitars which were met with an enthusiastic response from players. Several players especially liked the design and many of the earliest prototypes were sold to players the likes of Pat Metheny, Kenny Burrell, Kevin Eubanks, and others. Further designs and prototypes were built adapting the EC to electric as well as acoustic guitars and developing models for construction in any of the popular formats. Patents and trademarks were granted worldwide in the late eighties and instruments using the Extended Cutaway design have been built since.
Extended Cutaway guitars are currently being built and marketed world-wide by Stephen's Stringed Instruments and Washburn International.