Crossovers?

[Kevin Sjostrand]

I will sometime later this fall start my next two projects; another EIR dred and a nylon stringed crossover for myself.
My thinking is a OM body of curly cherry with walnut binding, bolt on spanish cedar neck, sitka spruce top braced of course classical style.
I have other woods I could use for this guitar, but I think that combination will look good but I haven't a clue on how it might sound.
Any ideas, thoughts, etc.???????

Kevin

[johnnparchem]

I think it would be a great project that will sound great. t is a I nice size and good choice of wood.

[Darryl Young]

If using nylon strings, I would use the lightest weight spruce I could find (Englemann, Lutz, or even cedar). Ask a lot of questions on how thin folks go. I would go as thin as possible for best response as you just don't have as much energy to work with using nylon strings. If you want to measure the stiffness, I have a spreadsheet with the formulas Trevor Gore uses and I can plug in the stiffness values and it will calculate the thickness Gore likes to use for classical tops. At least it would be a reference and you could determine the final thickness you are comfortable with.

You might consider an alternative to red spruce braces (unless you have some with abnormally low density).

Will you use a classical style bridge?

A guy at work wanted me to build him a nylon string, crossover style guitar. I build so slow and have so many things I want to play with first that I said not now. It does interest me, just other things in my mind I would like to try first.

Edit to Add: I've read Carruth (.....sorry Al if I mis-remember who said this) or someone state that the classical guitar body has about as much soundboard as nylon strings have energy to drive. In other words, going larger doesn't help. You may want to consider a 00 size body. Sure fun to play a 00 size guitar when sitting on the couch!

[Darryl Young]

Per chance you get fired up about a lightweight top but don't have one on-hand, I might be able to find a nice Lutz top in my stash you could consider.

[Kevin Sjostrand]

Darryl, you bring up interesting things to consider. I have plans for the OM, a small jumbo, and i have plans for a couple of classicals. I could certainly build a classical, but go 14 frets and narrow the neck, radius the fretboard, etc.
I will do the slot head, (first one for me) and I will do my own version of the classical bridge, probably more along the lines of what Taylor does on their crossover. I do not want the guitar to look like a classical guitar.
How much lighter is Lutz than Spruce, in general?

Kevin

[Darryl Young]

Hopefully Al or Rick will chime in here as everything I'm discussing is based on theory, not experience (I think Rick builds classicals.....I know Al does).

You must generalize when discussing density of particular species......so keep in mind that there could be an abnormally light/heavy example of any species when evaluating a particular top. In general, Red and Sitka are toward the denser end of the spruces and with Englemann and Lutz being lighter. I would probably rank them like this from densest to least dense (anyone feel free to shar your thoughts):

- Red
- Sitka
- Lutz
- Englemann

Again, that is a generalization and I've heard of very dense examples of Englemann (never heard of a very light example of Red spruce but no doubt they exist). Lutz is a hybrid between two spruces. If I remember right, a cross between Sitka and White spruce.

I love the shape and size of a 00 body. Lower bout is a similar size to a classical and the upper bout is shorter where a 14 fret neck works well. A lot of folks sell the same case for a classical and 00 (but it doesn't usually fit the 00 as well).

Another generalization. From reading Gore/Somogyi, with steel string guitars, treble comes natuarlly and you work to get bass from the instrument. With nylon classical guitars, the bass and warmth are there and you work to get nice trebles from the instrument. From Carruth/Gore/and my engineering background, weight of the soundboard and bridge acts as impedence to the string energy. The impedence mismatch caused from additional mass afffects the trebles more than the bass so you lose the high end faster than the bass end as mass is added.

So with that said, I would minimize the weight of the soundbaord/bridge/bridge plate as much as possible on a nylon string guitar as it gives you a better chance of not killing the treble/highs/sparkle of the instrument. The weight of the bracing is small compared to the weight of the top so I would focus on the top first by selecting a perfectly quartersawn example with no defects and minimal density........then measure stiffness or the weight/stiffness ratio to determine how thin you can go and then thin the top as much as you feel safe. Then be careful which wood you select for the bridge and remove all the mass possible from it.

A good question for Rick and Al is which bridge design should you use......classical (wider possibly heavier) or steel string style (potentially lighter? but needs a bridge plate). I'm unsure if you can find nylon strings with ball ends but if you use a steel string style bridge I would thin the bridge plate considerably more than when using a steel string.

[Kevin Sjostrand]

Good thoughts and ideas. Thanks.
I figure to do a bridge along the lines of what Taylor does on their crossovers, tweaked a little different shape. I don't want the standard classical guitar bridge look.
I am a big guy so I don't want too small a body, that is why I was thinking the OM. I've always played dreds.
I hope to be playing around with a layout design soon as I plan this guitar.

Kevin

[Darryl Young]

Will be fun to watch!

[Kevin Sjostrand]

Soooooo, I'm thinking of taking a drawing of the OM top, and taking a plan I have for a classical, and basically drawing the bracing layout onto the OM, stretching it here and there to "fit". Does this sound reasonable? The rest of the guitar will be like a steel string OM; little bit wider at the nut and bridge. The other thing I'm not sure about is if I should do 12 or 14 frets to the body. What do you all think?

Kevin

[johnnparchem]

I would go 12 frets to the body as it will lower the bridge to more in the center of the lower bout. Of course this crossover will be a cutaway?