11/06/2023
Completed Wenge back plate for a Model 3.
The massive transverse brace and the upper bout of the plate form the final component of the neck buttress system. The transverse brace also sets the perimeter of the vibrating area of the plate.
The X-brace in the lower bout is fitted with a threaded insert at its intersection, which allows for mass to be reversibly fixed to the plate in order to modify its resonant frequency. Although I'm not familiar with the details of his system or designs, I know that Bryan Galloup () has patented a similar approach in the USA.
Adding mass is always less desirable than removing stiffness when lowering resonant frequencies, since mobility is negatively impacted by increased mass. The difficulty with relying on the removal of stiffness through brace shaving, however, is that there is no simple way to recover stiffness or raise a resonant frequency once the material has been removed.
The fixing of mass to the plate will serve as a buffer during plate tuning - a few grams of mass will be bolted to the plate during brace shaving and tuning of the coupled top and air resonances. If anything goes wrong and the back resonance drops undesirably low, the mass can be removed for a second opportunity at dialing in the coupled resonances.
