Hi Ron Thanks for the thoughtful reply. Correct me if I am wrong, but what I am <<hearing>> is that if there is not enough cross grain stiffness in the middle of the soundboard... or better said out in front of the bass bridge and tenor bridges and a bit left of center pehaps... then the board will acoustically break up into many smaller vibrating areas and vibrate poorly as a single whole at its fundemental. And perhaps the same can be said of the first couple low vibrational modes of the panel. If this happens a thin, nasal like sound can occur because essentially you've filtered out the low end... and perhaps boosted some midrange frequencies, maybe even higher frequencies... depending on the over all stiffness elsewhere in the panel. I'm assuming that in just about any panel the along the grain stiffness is more or less a given and cross grain placement of ribs wont alter that. What you say about old panels pans out perfectly with what I am observing as well... and indeed this particular instrument I'm dealing with has been fascinating from several points of view. Every one of the pianists who period pianos for a living who has played this thing has loved it. Some have understood my own less then enthusiastic comments about the thinness of the sound... but insist this is how they are <<supposed>> to sound. Myself.. I have to think by mid 1850's piano sound was well on the way to approaching that Steinway sound that established itself some 20 years later. Looking at the ribs... listening to the sound.. I have to think along the lines you suggest... that the cross grain stiffness was in the panel itself because of compression. This jives well with the killer octave problem of today as well if I am not mistaken. Its harder to identify a lack of sustain in the longer strings perhaps... but that thin weak tone development is akin. If this is right then... it suggests a way of improving sound on any kind of instrument that suffers this kind of problem. Indeed the appearance of the so called riblets for the killer octave goes exactly in this direction, just applied to a different problem and a different area of the soundboard. One could either install rib height extensions or extra ribs as needed. It also raises several questions on both sides of the CC, RC, and RC&S discussion I'd like to see hashed through again. I cant help but think that a gut feeling I've had for many years now ends up being true. That at least while the elastic strength of the wood survives the compression strain the cross grain stiffness in the panel is more homogeneous then in boards with little compression used... hence creating a somewhat different overall sound picture. This would explain also what old panels that are carefully removed and turned into rib crown and supported panels apparently dont sound quite as <<new>> as one might expect. The trade off being longevity of that original character. Actually.. theres a lot I'd like to see discussed over again about all this. Cheers and thanks for the post... RicB 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
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