>Del, >I'd second the notion that soundboard characteristics change with load. >For SURE! > >While I'd agree that a modal analysis is meaningless without the full system >(strings), it can be very valuable calibrating FEA models. It's very simple >to add/remove components of a finite element model and is invaluable for >checking the accuracy of parts of a very complicated model (like a piano). > >I know, "so what are you waiting for"? >I'll get back to it ;-) > >doug richards >San Jose, CA Well, sure, soundboard characteristics change under load, but how much? My point is that we, or at least I, make design decisions based on how I think the board will respond in use, not how it sounds lying on the floor. I have no way to determine how the board reacts without the string load. I can't hear it without the strings, so I am, in effect, factoring the difference into the design. How well it works in use is determined by how good my initial design was, how accurate my judged factoring was, and the characteristics of the materials being used being what I thought they were. If we could compute an unloaded impedance gradient of the assembly, across the scale, with the physical information we *do* have, and working backward from the way it *sounds* in use, compared to what the computed gradient says, we should get both a roughly quantifiable cause and effect relationship (which we are already working with, without the detailed figures), and some idea of the difference between the loaded, and unloaded states. Again, I believe the differences between the unloaded state of the assembly, and the loaded state, can be quantified to a practical degree without taking a FEA model to the sub atomic level on every single piano that's worked on. The impedance loads, taken from the scale and bearing schedules should be relatively simply applicable to the computed static impedance model of the assembly, wouldn't you think? It ought to be proportional, shouldn't it? How close to an absolute dead center impedance match/mismatch is necessary before we are beyond the resolution (granularity?) of the medium with which we are working... wood? What the heck IS the ideal match between soundboard assembly and string plane, given high impedance mountings and terminations? That's what I was getting at. I suppose it's still a chicken/egg sort of thing though. Someone has to do it the hard way and make it work before it can be simplified to usability. I sure wish I could pound some of the missing math receptors into this old brain, I could certainly use them. Ron N
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