> There is simply no way any potential soundboard expansion is going to be > felt between the edges of the soundboard and the outer rim. This notion > doesn't even make any theoretical sense, let alone any practical sense. Ahhhhh, technically correct, BUT if does make MARKETING sense! If it sells - it must be right/best/whatever! Sad but true. Terry Farrell ----- Original Message ----- From: "Delwin D Fandrich" <pianobuilders@olynet.com> To: <pianotech@ptg.org> Sent: Thursday, September 06, 2001 10:24 AM Subject: Re: Baldwin SD-10 > > ----- Original Message ----- > From: "Farrell" <mfarrel2@tampabay.rr.com> > To: <pianotech@ptg.org> > Sent: September 06, 2001 4:48 AM > Subject: Re: Baldwin SD-10 > > > > > The soundboard was designed to leave it approximately 5/8" short of the > > > outer rim all along the perimeter. The rationale, if I remember > > > correctly, was to give the sound board room for expansion or contraction > > > depending on the season. > > > > So is the soundboard not glued to the inner rim so as to allow it to > expand > > to the outer rim? Or is it glued, and they simply designed the inner rim > to > > compress as the soundboard expands toward the outer rim? Kinda hard to > > figure. > --------------------------------------------- > > This subject keeps coming up in one form or another from time to time. > > There is simply no way any potential soundboard expansion is going to be > felt between the edges of the soundboard and the outer rim. This notion > doesn't even make any theoretical sense, let alone any practical sense. > > Most pianos have an inner rim that is somewhere on the order of 35 to 45 mm > thick. Even if the inner rim is coved in a misguided attempt to 'increase > the radiating area' there is still a minimum of about 20 to 25 mm of glue > surface around the inner rim. The glues or adhesives used to bond the > soundboard to the inner rim are typically quite rigid--that is, they do not > creep under load. They will fail before they will allow any creep. For any > soundboard expansion to be felt around the outside parameter of the board > there would have to be some slip across the glue line but, since the > adhesives used do not allow that, the only possible way the gap between the > edge of the soundboard and the outer rim could change after assembly is for > the adhesive to fail catastrophically--and that's a whole other issue. > > The same logic applies to the notion that the edges of the soundboard must > contact the outer rim to somehow 'reflect' sound back into the > soundboard--or whatever it is that's supposed to happen out there. As long > as the soundboard remains glued to the inner rim it simply doesn't matter if > the edges contact the outer rim or not. This may be an aesthetic > consideration to some, but it is neither a performance nor an acoustical > consideration. > > Del > >
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