Ron Nossaman wrote: > . . . . When the > mere act of touching the bridge pin terminating a beating string clears up > the beat, it ain't the soundboard design, or is it? Yes. You're altering the resonant frequency of the soundboard by touching the bridge pin. More anon... > The reason the board is > flat enough to make the bearing light enough for this to happen in the first > place is, indeed, a soundboard design problem. So it is a soundboard design > problem at root. From a service standpoint, it's probably a loose pin that > never would have manifested any noticeable symptoms if the bearing was > adequate, assuming it was set within reasonable limits in the first place > and the soundboard was doing it's job. It's not even so much a matter of soundboard system crown. I'm not convinced that within reasonable limits the lack of crown and/or bearing has much of anything to do with pins coming loose or staying tight. It does have to do with soundboard springiness. Certain piano simply have a predisposition toward false beats. Others do not -- even with loose bridge pins, etc. (See below.) If -- when, actually -- the former develops false beats there is not much you're going to do to make them go away. No amount of CA, string seating, pin pounding, whatever is going to alter that. You can sometimes improve things a bit with all these heroics, but the results don't -- won't -- last. If the latter develops a few false strings a light tap on the string usually takes care of it. Then, of course, there are those in the middle. . . . OK. So, here is the short and sweet version of the principle: If the fundamental resonant frequency of the string loaded soundboard assembly at the point of contact with the affected string is higher than the fundamental frequency of the string, the motion of the bridge tends to follow the motion of the string and the string sees both the actual speaking length and some artificially longer speaking length. False beats will readily develop and will be nearly impossible to control. If the fundamental resonant frequency of the string loaded soundboard assembly at the point of contact with the same string is lower than the fundamental frequency of the string, the motion of the bridge will tend to oppose the motion of the string and the result will be a cleaner, more efficient termination of the speaking length of the string. False beats will show up more rarely and will be easier to treat. Modern soundboard design can -- should -- provide a balance between the requirements of low mass, reasonable elasticity, etc. to give both good power and good sustain while still providing an acceptable tolerance toward false beating. Obviously. Some piano designs have already come very close to meeting this goal. And, no, I'm not going to go into specific design details on the internet. . . I'm not yet that altruistic. > Since most techs aren't likely to > correct basic soundboard design problems in a service situation, or even in > the rebuild shop, it has to be dealt with from the wrong end. We usually > have to deal with the cause that's closest to the symptom. CA the pin and go > home. I agree that you have to do whatever you can to attempt to make these things go away. Just don't beat yourself to death if your best efforts are not all that successful. It ain't your fault. > They'll be using different glues too. What? Better than CA . . . . ? How could that be? > Serves you right, troublemaker. Did you get your head working? <Evil Grin> > > Ron Which "head" are we talking about here, Ron? If we're talking about the one on the boat, yes. At least it's working about as well as it's going to work. If we're talking about the one I normally carry around with me -- well, that one hasn't been working right for years.... Del
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