Del, This is extremely interesting. More and more I'm finding myself more fascinated with inherent design flaws and our attempts ( in the field) to overcome them. In the "real world", the world in which we has technicians have to make things work, many times on a paper-thin budgets, ideas like this gets my head spinning. I have a few little grands in the shop which just might find some experimenting R&D time this week with this idea. As always,thanks for your sharing your expertise. Your willingness to share your ideas benefits all of us. Tom Servinsky,RPT ----- Original Message ----- From: "Delwin D Fandrich" <pianobuilders@olynet.com> To: <pianotech@ptg.org> Sent: Saturday, March 09, 2002 8:41 PM Subject: Soundboard Weights > > ----- Original Message ----- > From: "Tom Servinsky" <tompiano@gate.net> > To: <pianotech@ptg.org> > Sent: March 09, 2002 12:45 PM > Subject: Re: What a nice surprise - technically OT > > > > > > > > > > Normal pradctice is to harden the hammers. An effective compensation > > > is to secure weights to the bottom of the board. Or replace the board > > > with one properly designed and assemsbled. > > > > > > Newton > > Adding weights to the bottom of the board is a new on me. Would please > > elaborate. > > Tom Servinsky,RPT > > > > Tom, > > Soundboard impedance is established by three primary characteristics of the > soundboard assembly; its mass, its springiness, and its internal resistance. > With most of the pianos exhibiting 'killer-octave' problems the problem lies > with the reduction of springiness that has taken place in the soundboard > assembly relative to the time when the soundboard assembly was new. Or at > least when it was functioning properly. There is nothing you can do about > the systems internal resistance and there is not a lot you can do about the > loss of springiness except add auxiliary springs to the system, but this is > a technology that few have yet to embrace so little is known about the > procedure or its long term results. > > The other thing you can do is add some mass by means of brass (at least that > is what I've used) weights attached to the underside of the soundboard along > the bridge line. These are installed by drilling through the brass weight > (start with something in the neighborhood of 75 to 100 grams) and screwing > it to the bottom of the board. The screw should extend well into the bridge > body. Put one in the area of shortest sustain and see what happens. You will > have to experiment with various amounts of mass to find the amount that > gives you the best results. Once you've settled on a certain amount of mass, > put a bit of PVC-E adhesive between it and the soundboard (to keep it from > buzzing) and tighten the screw thoroughly. Several weights in the 75 to 100 > gram range spread between the various ribs are better than one two to three > hundred gram weight stuck in just one place. > > This is not the same as a new and functional soundboard, but it is a lot > cheaper. If you don't like the results you get from these weights simply use > a screw and soundboard button on to cover the hole(s) you've made and forget > it. A new soundboard will then be the only solution. > > Del >
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