>The idea of laminated soundboards has me musing over this little poser... Me too. Though I haven't built one, a few possibilities have occurred to me, some of which may even be valid... maybe not. >If we're dealing with a laminated soundboard panel, how important is grain >direction? With a solid spruce panel, you can steer the stiffness of the panel somewhat with grain angle from the belly bar, and rib angle relative to the grain. Like you said, the laminated panel could be made stiffer in one direction, like the spruce panel, and get a similar effect. Reproducing a spruce panel with a laminated one with the same or similar physical characteristics doesn't teach us much of anything though, and that's what has been the problem with attempting to use laminated panels in pianos. Not much has been done to learn to accommodate the characteristics of the medium. I would like to approach it from starting with a dirt dumb simple cheaply and quickly produced isotropic panel and attempting to find out what it takes to make it behave like a real soundboard. What would be a good material to build it out of? I would think something of a stiffness, elastic recovery, internal friction, and strength to weight ratio average somewhere between spruce and mahogany, would be attainable as a start. It needn't necessarily even be wood. Since the laminated board doesn't have the flexibility across grain (roughly parallel with the ribs) like a spruce board, and would necessarily be denser than spruce, I would think it couldn't be as thick as a spruce panel. Say 4 millimeters as a starting point, depending on the actual stiffness of the material used. That ought to give us adequate flexibility along the ribs, but too much along the bridge. Since I don't really know how much support the long grain stiffness of the spruce panel ties the entire diaphragm of the board together, I'd probably try more, and smaller ribs than "usual" to minimize panel flexibility between ribs without adding unnecessary weight. I'd expect to have to pay closer attention to bridge placement, proximity to the rim, positioning on the ribs, and overall length and cross sectional dimensions for stiffness control, rather than relying on the anisotropic characteristics of spruce to stiffen the assembly along the bridge line. I might want to add a couple of ribs on top of the panel, as further compensation. Then again, it might not prove to be necessary. Since I couldn't get the added panel support resulting from a moderate drying and re expansion after assembly, I'd dish the rib press more than the machined crown(s) of the ribs to build in a little panel compression. Normally, a soundboard assembly acts as a variable rate spring, with resistance increasing as it is loaded. Most of this comes from panel compression, and the thicker the panel, the steeper the spring rate gradient. It's a leverage thing. With my expected thinner panel, I would think I'd have to dish it a little deeper, leaving more compressive force along the ribs, to get a similar action. Then again, maybe not. The first one built should give some indication either way. After pondering on all this stuff, and a lot more, through the building of the first one, I'd string it up, listen to the result, think about what I could do differently to correct the initial mistakes, and build another one. Re think, rough in, experiment, refine. Repeat as necessary, as long as possible. I'm interested. I wish I could afford to try it. >As an aside, I did see an example of a laminated spruce soundboard in a new >piano recently. (I can't remember the name, was it Story & Clark maybe?) >They used a solid spruce core and spruce laminations on both sides. I did >think it was somewhat fascinating that someone would go to that trouble, >although I would think it might be slightly more stable with changes in >humidity. > >Brian Trout Wurlitzer used (uses?) one like this. I don't know who else has tried it. Regards, Ron N
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