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From: Ross
Remote Name: 76.101.10.136
Date: 07 May 2007
Time: 09:26:30 -0400
Luthier’s Weblog 5/7/07 How does one build a guitar neck in such a way that it enhances sound? My robot luthier starts by considering energy management. A particular string, of his chosen scale length, at a particular pitch, when driven by a given input (plucked or picked), will respond by dissipating that input energy by transferring it directly to the air and to each anchor point. Little energy is lost to air resistance. The bulk of it is transferred to the anchor points. One of these anchor points is the guitar’s bridge. The other is the headstock, via the nut and tuning machines. The body (specifically the top) is the business end of sound propagation. Here, the energy is transferred from the bridge to the top surface where it strives to overcome the top’s reluctance to begin moving air (inertia) in order to create some sound waves. Once the top begins moving, the frequencies propagated are roughly the same as the frequencies at which the string is vibrating. Energy that ends up in the form of sound waves, however, is typically no greater than 5% of the energy imparted by the right hand to the string! Fully 95% of the energy is lost in the form of heat generated by overcoming inertia. Which returns the luthier’s attention to the neck. The luthier wishes to transfer as much energy to the top as possible. But the string is also anchored at the headstock. Surely some energy is lost here, too. The ideal guitar, he reasons, would transfer 0% energy to the headstock and 100% to the soundbox. He further reasons that the neck, therefore, must possess infinite inertia, or resistance to movement. This seems difficult to achieve. Perhaps a brass plate attached to the headstock? Already commercially available, the Fathead ™ adds mass to existing headstocks to achieve this very end. Widespread acceptance has eluded the invention, however; possibly because the left hand must support the neck in addition to fingering duties. The builder does not want to unnecessarily increase mass for ergonomic reasons. He feels that the only avenue open is to increase the stiffness of the neck. This may be achieved through the use of alternate materials, such as aluminum, steel, or graphite. Also by selective building techniques, such as lamination, wood grain orientation, polymer saturation of the wood. The luthier’s experience with metal necks has not been uniformly satisfactory. He believes that the “feel” of wood is more ingrained (ha ha) experientially in the average player. Graphite necks feel very similar to wood, but the very stiffness he seeks is at odds with the need of the builder to be able to alter neck relief to accommodate playing style. He settles, therefore, on a compromise of traditional wood construction, with the addition of a thin, rectangular carbon fiber rod inlaid in the neck blank on either side of the truss rod. Stiffness is greatly increased, as is the resistance to twisting. The truss rod can still exert enough influence to make the required relief adjustments. With the ebony fingerboard in place, less energy is lost at the headstock end, with a resultant increase in the amount passed on to the bridge. Ross Teigen 9:07 am