Richard and all, This is the line I was waiting for someone to contribute, and uncle Jim was the one who did it. Thanks Jim. >. . . We try to make the board stiffer in the middle and more >flexible around the edges so it will vibrate as a unit at low frequencies >instead of breaking up into standing waves. . . . >Jim Ellis Several commentators have said that they believe the board is too stiff. But the further qualification which we need to answer is, ". . . too stiff where", which may lead us to conclude that the soundboard might not be stiff enough. I've looked at images of the piano around which this topic is focused, and to me it looks like the board very likely has insufficient stiffness in the middle area of the panel to act as an effective low frequency driver. Now some might say, why then did the original maker build the soundboard with these dimensions? Well this design probably was originally built as a compression crowned panel. So it would have somewhat-worked for a time. I say somewhat worked, because I believe that almost everything I've seen which was built between 1860 and 1880 had grossly insufficient panel stiffness when compared to some of the more effective later designs (its always easy to be wise in hindsight). Again, some will claim that these older boards have lost their stiffness with time. Yes they will have. But if you build a replacement panel for instruments of this period, using the same physical dimensions, they will exhibit a quite similar tonal quality, in spite of the fact that the soundboard is new. I believe it comes down to insufficient belly stiffness. Sure the rim weight/stiffness will play a part also, but the soundboard design along with the choice of hammer will be, above all else, the two principle factors which determine the overall tonal outcome. When thinking about the desired physical characteristics of a sound board assembly, remember that while the very best low frequency speakers have a flexible perimeter region, the cone itself is reinforced to increase stiffness and reduce standing waves. Watching standing wave patterns form on a driven panel might look very interesting, but the propensity of the panel in itself to form standing waves is not helpful. We really should be trying to reduce them. I believe an effective design can help to minimise their influence over the tonal outcome. Considering where to make a board stiff and where to make it flexible, would seem to be a major priority. Much of the sound board tone building equation comes down to a relationship between area/stiffness/mass per unit area. I don't know of anyone who has a magic formula for determining how much of what is desirable, but there are answers out there in waiting as the 'circle gets smaller'. Ron O. -- OVERS PIANOS - SYDNEY Grand Piano Manufacturers _______________________ Web http://overspianos.com.au mailto:ron at overspianos.com.au _______________________
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