That's exactly what I was suggesting, but I don't know if it is so. You're right, it's the only way for a crown to be like a section of a cylinder instead of a sphere, but that's what I was picturing that Bluthner was saying. Does it seem really out there to you that Bluthner shapes the top of its rim that way? Does anyone know what a Bluthner rim is like in this respect? -----Original Message----- From: Farrell [mailto:mfarrel2@tampabay.rr.com] Sent: Wed 1/28/2004 2:50 PM To: Pianotech Cc: Subject: Re: Permanent Soundboard Crown! Are you suggesting that the inner rim is taller at the rear left and front right corners of the case (referenced from the pianist sitting at the piano)? If the rim is at a constant height, i.e. within a plane, then how does the board form a cylinder as opposed to a paisley-shaped dome? If the edges of the board form a plane, and the board is taller in the middle than the edges, then you will end up with some form of a dome. And furthermore, I would suggest that if the middle of the soundboard is, let's say, 6 mm above the rim, then you will have 6 mm of crown as measured parallel with the ribs (crossing the middle) and you will have 6 mm of crown measured perpendicular to the ribs (crossing the middle). How else could it be? So what is the difference between cylindrical crown and spherical crown? Now of course the curvature of the soundboard perpendicular will be of a larger radii than that parallel to the ribs, but only because it has the same amount of crown over a greater distance (assuming we are not talking about a micro-grand). Terry Farrell I took "cylindrical curvature" to mean that the sheet is curved along the diagonal-ish line of the ribs, but flat as measured across the ribs. Trent Lesher Studies made by Bluthner research and development department have proven that tensions and compressions develop on the edges that are inhomogeneous and not controllable. In contrast, the soundboard that Bluthner has developed has a cylindrical curvature so that the tension of the soundboard can be exactly defined. The ribs are planed to fit the curvature needed and therefore the tension of the soundboard remains intact over the decades. In fact, even under difficult climatic conditions the curvature will remain in a constant form since not only the rib structure will hold it in place but also the red beech inner rim is preformed to the correct angle to receive and retain the soundboard's curve tension. Because the soundboard is pre-stressed in this fashion it can be fitted exactly and remain under curve tension permanently. The bridge, of course, is adapted to the tension and curvature of the soundboard in its optimum position. This ensures that string vibrations in their full spectrum are transferred to the soundboard. By utilizing the resonating surface, the special design of the Bluthner soundboard generates tone significantly better. The way I understand the above text, Bluethner uses crowned ribs and doesn't rely (at least not much) on panel compression to achieve crown. They want a cylindrical crown, as opposed to the spherical crown advocated by piano designers such as Klaus Fenner, who wants the board to be curved not only along the ribs, but also (roughly) along the bridge, with a high point at a certain location. Fenner favours compression-crowning and has some theories about stresses that need to exist not only in the soundboard, but also in the rim etc. to get a good sound. I've read both Klaus Fenner's and Ingbert Bluethner-Haessler's books on piano construction, that's how I learned about the differences. The text posted by Terry F. is pretty confusing when taken alone - probably because it is translated from German ;-) Calin Tantareanu ---------------------------------------------------- http://calintantareanu.tripod.com ---------------------------------------------------- ****** IMPORTANT NOTICE ****** This e-mail, and any attachments hereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments hereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify me at (312) 207-1000 and permanently delete the original and any copy of any e-mail and any printout thereof.
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