Acoustic Guitar Construction

Yeah -- the dome, another dimension taken after the instrument was on the planet 80 years! The dome is from string tension -- actually you'll see that once you take the plate with the braces glued in place the dome will just about disappear anyway, the fan braces don't hold shape and what else is there in the structure to do so? The classicals I built where based on the methods and techniques laid out by Sloane and Overholtzer. All easy players in the end. Overholtzer warns about trying to dome the sound board says "it diminishes sound quality", Sloane points out that the ladder brace is only slightly domed on the outer edges to prevent the look of a concave top. Perhaps I should just shut up -- sorry, I have the full blown LMII Hauser print package and I see a lot on the Brune drawing that does not make sense.

No no no, don't shut up! :) This is all very helpful. You have a lot more experience then I do, as many of you here do, and all I've built are steel strings!
I was wondering how well those thin braces would hold the radius, and figured they would not much so another variable to the equation, right?

Ken, I agree with you that tilting the neck forward complicates the construction and is not necessary to construct a classical guitar. I am not so sure that that classical guitar builders pitch the neck forward because of conventional wisdom based on measurements of old instruments. There are numerical reasons that the geometry of a steel string and a classical are different. The main 2 reasons: the optimal height of the strings over the top at the saddle is 2-3 mm lower than a typical steel string. One can have the same height as a steel string but the sound is less "classical" (more of a leading pop); the second reason is that the action at the 12 fret of a classical needs to be 1 to 1.5 mm higher than a typical steel string.

On a steel string I look for the neck angle to result in a 2.5 mm clearance at the saddle location using a straight edge on the neck. With a classical taking into account the desire for a lower string height over the top and the required higher action one can see that the angle of the neck (assuming a non-tapered fret board) requires that an imaginary straight edge on the neck should result in about a -2 mm height at the saddle location. Purely on numbers the negative clearance would be a bit deeper but the top is going to dome a bit from string tension, even if the dome is not built in.

That minus 2 height is why some builders pitch the neck angle forward a bit. I have seen a few ways to achieve this geometry, build flat and taper the fret board such that a measurement at the 12 fret is about 1 mm thinner than the at the nut. This taper is in addition to the taper thinning toward the bass side of the fret board. Tilt the neck forward, requires that the neck extension is tapered to sit properly on the body. An elevated neck extension with the proper geometry built in, eliminating the neck body mismatch. Also I have seen the use of a long wedge the elevates the fret board at the nut and tapers down to nothing as one reaches the sound hole.

All of the above methods are used to achieve the desired geometry for a classical guitar.

John it would seem to me that tipping the neck forward combined with the doming effect of the string tension could equate to far more than a negative -2mm at the saddle location. Maybe I am not visualizing this properly.

That said, I have never heard/read (which actually does not mean a thing) that this is the definitive design requirement for making a nylon string guitar sound like a "classical" Having heard hundreds of classical guitars with different bridge/saddle/finger board/neck configurations including hand made, top of the line imports -- Takmine's and Avarez in particular, Old Martin N20's with a bridge saddle height of almost 1/2" that sound really great (to my ear).

As for cross-overs, its my view that these are designed mostly for playability -- and I think electronics generally come into play any how.

Ken I agree with most of what you have said, especially with regard to a crossover. Pitching the neck forward or worrying about some ideal classical sound is not important, as this instrument is a nylon string guitar not a classical guitar. I also think that plenty of classical guitars that do not match the ideal geometry sound absolutely great, but still they still might not have the ideal classical sound and response that a guitarist like Julian Bream would want.

The geometry of both the pitched forward neck and the domed top does work. I have built two classical guitars pitching the neck forward a touch and building in a dome, and each time once set up I nailed the 11 mm height of the strings off the top at the saddle location I was trying to achieve. But alas I still do not think a guitarist like Julian Bream would want either of them. But the geometry did work and both are good sounding classical guitars.

The main point I had in my other post is that the classical guitar builders rightly or wrongly are designing to a geometry, for a desired result.

Most helpful, keep going!!!!
Now I am thoroughly confused.......just kidding.

Talk about geometry -- how about a Humphrey design? These have lattice bracing as well. Martin was licensed to make these for a while --- real nice sounding guitars now worth more than they cost new.