Hi Steve: Thanks for the post. I wont pretend to know one way or the other for sure mind you. But it does strike me that as a consequence of compensating for anisotropism that both the bending stiffness and speed of sound in both directions are evened out. Since it is sound (waves) traveling through that actually causes whatever vibrational motion soundboard displays.... its strikes me that speed of sound in all directions is an intregral part of that motion. Be that as it may... lets just agree on the exact quote from Wogram and get back to the main question I had. He said "From the measurements it can be concluded that the two most important functions of the ribs are to stiffen the soundboard and to compensate for the differences in bending stiffness parallel to and across the grain (anisotropism). The bending stiffness exerts a greater influence than the mass. For this reason it is more advantageous to use narrow, high ribs than ribs with a low and wide section." What I'm thinking about is that in principle achieving equal bending stiffness in both directions is in itself an independant objective from supporting crown. However In boards that have the grain going in the same direction as the bridge these two requirements must be balanced against one another.... perhaps even to some degree are at odds with one another ? On the other hand.. if you built a soundboard with grain going perpendicular to the bridge and were able to establish enough crown support along the grain by way of cauled laminants all going in the same direction, then ribbing across grain could be used exclusivly to equalize bending stiffness. It strikes me that the soundboard needs crown support more in the direction perpendicular to the bridge then paralell to it. The bridge itself is very stiff lengthwise to begin with. The need for support perpendicular to the bridge appears (to me at this point) to be one of the primary reasons todays soundboard construction uses ribs in that direction which in turn requires grain to go paralell to the bridge. There is much about all this I dont understand.... but I'd like to hear what problems this kind of configuration would have. Cheers RicB Ric, I doubt Wogram is referring to the speed of sound within the mass of the soundboard when talking about "vibrating area" and "radiation efficiency". Isn't the sound we hear primarily a result of the diaphragmatic motion of the soundboard disturbing the air? Imagine a square soundboard with the grain running parallel to two of the sides. If the soundboard bends easier across the grain than parallel to th= e grain, then the shape of the fundamental diaphragmatic deflection will be more rectangular than square. Then if you add stiffeners perpendicular to the grain to equalize the stiffness, the shape of the deflection will be more square, and the "effective vibrating area" will be maximized. Respectfully, Steve Fujan
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