The Luthier Community

RIGHT ON, TL - Most cool!

E

Hey David,

Think of it like a timpani drum. You have the membrane but you need to screw it down to tone it up. The inside top is slightly thinner than a normal top and I needed to tone it up a little. Timpani and snare drums are screwed down tight, and I figured why not! Plus it gives me a reflective sound board that I can shape for the tone I want or at least work to tone, and... I had all of the scrap wood as stated above. I didn't trust a simple reflective membrane to push. I thought it would absorb more then it pushed if I just left it unbraced and if you've ever put your hand over a sound port and felt the vacuum of air movement inside the box you know that the normally stiffly braced back does have it's purpose managing that movement, and this is basically a "hidden" back. I think that covers it (racking my brain to think of what I thought about as I decided to brace or not). I have no idea, honestly, but I do know that the Contreras is braced. I've seen it. Or at least the swelled grain from the glue.

Dennis,

The Ramirez Camara Model does have a hole. http://www.guitarrasramirez.com/english ... nalEn.html Roll all the way down to the bottom of the page and you'll see. They have their top maybe an inch, or just over, or so below the 1st top. I've played both a spruce and rosewood camara model. Super loud and well worth the $$.

Most interesting Todd! ......so the end result is actually two *chambers*? If so, kinda reminds me of the old school passive radiator speaker systems. Am I gettin' warm yet?

OK Todd, now I see what Ramirez is using. Looks more like overgrown internal body mold/lining combo. Bet those sides are stiff! They claim it kills wolf notes, and that kinda makes sense as the internal volume has not changed a lot but the volume is broken up into smaller chambers. If a wolf not could occur, maybe it is beyond human hearing (but I bet a wolf could hear it!)

Just for another spin on this, Nick O has just shown a double back guitar on the ANZLF, and has a breather vent to allow some air exchance between the main internal cavity and the cavity between backs. Variations on a Macca

Dennis

This is pretty cool stuff Todd. You should have thrown some brownies in the oven too.
So I can see where this also related to the Maccaferri style also except you aren't putting in the smaller ribs. Have you given thought about the the second soundhole or port or what ever it might be called possibly actic also like a baffle? Also I wonder if using a carbon fiber strips laminated in the braces would add to the volume. Mario Proulx uses them and says that they have a memory.
Thanks for sharing this. I know what it takes to makes these tutorials and I'm glade to see someone making some that I can learn from. Keep 'em coming
Edit:
I guess I should have read Dennis' link first.

Glued in the 2nd layer of back kerfing and glued on the back. The back braces are radiused to 15' to hold the back arch.

Todd,

I really like this idea and apreciate you posting the pics. Very nice looking Sapelle too.

I certainly know nothing about this design but my gut reaction would be that if a soundhole/port isn't added to teh middle back, pressure in the sealed lower cavity might limit or inhibit the vibration of teh middle back plate. Thoughts?

Welcome Darryl and thank you for posting something - So many folks, so few communicate!

Urb