[Tom2]

With the increase of interest in crossovers, due mostly to Emerald's custom options, I would like to share an observation about nylon in general. This may help people design a more desirable guitar.

Classical guitars are extremely well designed, and any deviation for crossover purposes must have a reason. Clearly, a narrower neck, radiused fretboard, and rounder neck profile make a crossover more comfortable to play for traditional steel string players. This is a good reason, because comfort is king.

Bridge position, however, is an issue. All classical guitars (that I know of) place the bridge in the 12 fret position, which is in the center of the lower bout. Classicals are available with scale lengths of 660, 650, 640, and 630mm lengths, and they all place the bridge in the 12 fret position. This is not a random coincidence, there is a reason.

Steel string guitars typically have a 645-650mm scale length for 14 fret designs, and a 622-632mm scale for 12 fretters, also for a reason.

Here is the issue. Crossovers are modified classicals, not modified steel string guitars, because string tension is the defining parameter in guitar design. Since most classical makers don't deviate from their classical design, hence the designation of "classical", most crossovers come from steel string makers who are accustomed to designing long scale guitars as 14 fretters. This is a mistake.

The reason why I bring this up is because, in another thread, I noticed that Ted said Rainsong NP's were tried with a long scale, thinking that the greater tension may help with projection, but it didn't. My guess is that a longer scale would help the NP, but that this benifit is negated when the bridge is shifted from the 12 fret NS position to the 14 fret N2 position. Also, photos of Emerald's X20 Nylon and Evan's X10 Nylon reveal a 14 fret design. The simple truth is that nylon strings need a bridge in the center of the lower bout, and here's why.

100% of the energy in a guitar comes from plucking the string. Three things can happen to this energy.

1) It is transmitted from the string, through the bridge, to the soundboard.
2) It is reflected off the bridge, back to the string.
3) It is absorbed by the string as heat.

1+2+3=100%

The 12 fret bridge position is more efficient at transferring energy to the soundboard, accentuating the fundamental tone and lower harmonics. The 14 fret position is more effective at reflecting energy back to the string, creating more sustain, and accentuating upper harmonics.

With steel strings, this is great because it gives the designer two distinct options that are both desirable in different situations. This is not true with nylon strings.

Nylon is so soft, relative to steel, that much of the original energy is absorbed by the string as heat. Because of this, nylon strings naturally have shorter sustain and fewer high harmonics than steel strings, negating all of the benefits that come from a 14 fret bridge position. Nylon strings have a strong fundamental, low harmonics, and dissipate energy fast. The 12 fret bridge position in the center of the lower bout is the only way to get the most from them.

Or, maybe I'm just making this up in my head (but I am classically educated on the topic of energy transfer at boundary conditions). Food for thought, at least.