----- Original Message ----- From: "Phillip L Ford" <fordpiano@lycos.com> To: <pianotech@ptg.org> Sent: January 06, 2002 1:17 AM Subject: Re: Stein grand unique board > But I question whether having them reflect back > from the rim is necessary for the soundboard to serve its function in the assembly > or whether this wave traveling and reflection is really the thing that we need to > worry about in designing a soundboard system. Any movement of the rim assembly will detract from the amount of energy in the soundboard system still available to produce audible sound. The energy to produce that movement has to come from somewhere. > If you can separate the soundboard > completely from the rim (I realize that the Stein was not completely disconnected) > and have it still function properly in the assembly, then perhaps the conventional > idea that the rim needs to be heavy to 'reflect waves' is not correct. That Stein soundboard system was/is not even close to being completely disconnected from the rim assembly. Nor were those of the run of new some pianos I examined a while back in which either the rib notches had not been cut deeply enough or the rib feathering had not been taken down enough--or both--and the soundboard was held off the inner rim surface by about 3 or 4 mm. A floating soundboard? No, it was still held in place by the ribs. Though, in this case, perhaps not for long. > Or perhaps the idea that the rim needs to be heavy is correct but > for a different reason. One way to design would be to do as Ron N suggested. > Make the rim heavy so that you essentially have an inert attachment for the > soundboard. > We know this works, and can work well. It also eliminates one of the variables that > you have to worry about. > But, as you say, the assembly works as a whole. Perhaps the rim should be one of > the variables. Perhaps if you had a really thin rim, or a solid rim with a knife edge > sitting on top of it that the soundboard is sitting on which allows it to act as a simply > supported member, or some other idea I haven't thought of yet you might get a sound > that is more to your liking. Since the assembly works as a whole, chances are if you > use one of these other rim designs you will have to change your board design, and rib > design, and bridge design and you'll be giving up the opportunity to use a couple > hundred years of accumulated wisdom but you might have some fun in the process. The rim is one of the variables. In the current scheme of things soundboards work best when attached to a rim that is both massive and stiff. Ron is not alone in saying this, nor is he the first. Nor was I--the notion goes back at least 125 to 150 years, probably some longer. I don't know if lighter, more flexible rims can be made to give equivalent (or better) performance with soundboard systems using totally different design concepts. I've not heard a piano yet with a 'Select Hardwood' rim that I really liked all that much, though some are certainly a lot less bad than others. I do know that Baldwin's experience was not good when they tried arbitrarily changing from a maple rim to a poplar rim. I also know that our own experience was not what I expected when I put one of our soundboard systems in a Yamaha with a light and flexible rim. As long as the perimeter of the soundboard is fixed to the rim, be it either clamped-edge or a hinged-edge, there are going to be energy losses to the rim. The only way around this that I can see is to convert to a fully piston-mode diaphragm (i.e., like a perfectly rigid loudspeaker cone) operating completely independently of the rim. Which might well be doable but I'm not going to spend a lot of time on it just now. So, in my opinion and using soundboards of either more-or-less conventional design, or of some other design but still fixed to the rim, I also say that the rim, being part of the overall system, should be both massive and stiff so that it does not readily absorb energy from the vibrating (and bending) soundboard. Del > > Phil F > >
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