> I have a question that I suspect maybe only Del or Ron N or Ron O might > be able to answer. > > In Del's class on small piano design, he has talked about > characteristics of soundboard design that will greatly influence the > tendency for a piano to exhibit false beats. I forget what that > explanation was. It may be related to stiffness, maybe impedance - > something like if the impedance of the board is greater/lesser than the > note frequency in that area of the soundboard the piano will/won't be > prone to false beats. > > The bottom line was that if the soundboard is poorly designed in this > respect, almost any defect in wire or terminations or whatever will > cause false beats. However, if the soundboard is properly designed in > this regard, even a loose bridge pin or a kink in the wire will likely > not produce a false beat. > > What is it about soundboard design that influences the tendency for the > piano to develop false beats? Ron? Ron? Del? Anyone else? > > Terry Farrell It's when the treble is quite stiff, but doesn't have enough mass. The sound produced is nothing like the false beats caused by loose bridge pins, and doesn't respond to the screwdriver test. Nor does seating strings do anything to clear it up even temporarily. It affects areas, rather than individual strings, and makes a nasty screechy super garbagy short sustain sort of sound. It really screams, rather than producing beats, and the cure is to add mass. Clamping a Vise-Grip to a bridge pin will make a noticeable difference in an area, as a diagnostic indicator for this one. Here's what happens : http://www.kettering.edu/~drussell/Demos/SHO/mass-force.html The fundamental resonant frequency of the board is higher than that of the driver (string hz), and overruns it. Adding mass lowers the resonant frequency of the board so it follows the string as it should rather than getting ahead of it. The problem that is always dragged into any discussion of false beats as quickly as possible is lack of differentiation as to what is being discussed, and any sound production anomaly heard anywhere in the piano is called a false beat. Since people are talking about so many different anomalies under one label, there is naturally not going to be one fix that takes care of all ills, or one explanation that covers all possible contingencies, and little is learned or understood as a result. This seems to be entirely intentional in at least some cases. Not yours, Terry. The easily verifiable fact remains that the majority of individually beating strings in the top half of the scale are the result of loose bridge pins. Ron N
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