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The question was: would a double-cutaway affect the sound?
The answer: a cutaway, even a double-cutaway, won't affect the sound as long as it is correctly designed. While it is true that simply adding a cutaway to a traditionally built guitar will change the sound, the luthier can compensate for these changes by redesigning the structure of the cutaway area. Let's look at how cutaways can change the sound, and how my designs address these problems.
Cutaways change the structure of the guitar in three ways:
- They take away some surface area from the top
- They take away some of the internal air volume of the guitar body
- They change the load-bearing structure which supports the neck
My double-cutaway design addresses each of these changes:
- Top surface area: Traditional non-cutaway guitar designs use heavy bracing around the soundhole to support the fretboard and to resist the constant pull of string tension. This makes the area of the top above the waist (the "upper bout") acoustically dead. Removing surface area from the upper bout doesn't take away any part of the top that contributes to the sound.
- Internal air volume: The size of the internal air volume of the body coupled with the soundhole determines the frequency of the main air resonance of the guitar body. This resonance reinforces the bass register of the guitar. When players block the soundhole to reduce feedback in amplified guitars, they are dampening the main air resonance, since the bass register is the most common source of feedback.
It turns out that the frequency of this resonance is relatively insensitive to changes in air volume. The amount of air lost in adding a cutaway, even a double-cutaway, is not enough to shift it audibly. This is why there are so many different sizes of guitars available, and yet they all still sound like guitars. The difference in the sound between an OM and a Jumbo, for instance, is mostly caused by the change in the lower bout surface area and a very large change in internal air volume.
- Structure: This is the most significant affect that cutaways have on the sound of a guitar. The shoulders of a non-cutaway guitar form a convex curve, which is an very rigid structure, like an eggshell. Adding a cutaway changes this to a concave curve, which is a very flexible structure, like a leaf spring. The rigidity of the neck-to-body juncture is a critical factor in guitar tone, directly affecting sustain and midrange response. The challenge in designing a cutaway is to recover the lost rigidity.
My double-cutaway design uses a system of internal bracing which supports the neck at least as well as the convex shoulders of a non-cutaway. I laminate mahogany with graphite to form extremely rigid flying braces which are let into the headblock and which extend to the sides at the waist. This transfers the load of string tension on the neck directly to the convex curves of the lower bout. The sustain and midrange response are restored and even improved over non-cutaway designs.
The picture below shows the flying braces in my design. While the braces appear large, they are quite thin and do not add significant weight to the guitar.
In short, by maintaining the structural integrity of the upper bout while leaving the lower bout uncompromised, my double-cutaway design produces guitars which are acoustically the equal of the finest non-cutaway instruments. |
