Ron Nossaman" wrote Sunday, January 25, 2009 12:28 PM <snip> Rebuilding with an existing board, thinning the bass (or channeling like Overs and Seiler) can be very worthwhile. Can you explain how you do that? Al -------------------------------------------------- From: "To: <pianotech at ptg.org> Subject: Re: [pianotech] Diaphragmizing > > >> Many people do it and the practice has been Steinways for some time. I'm >> curious about when Steinway actually started the practice and since I >> haven't taken out many Steinway soundboards that are newer I'm curious >> what >> their current practice is and whether other makers historically have >> employed this practice. I always thin the boards I do in the bass >> section >> graduating down to about 5 mm by the time one gets to the edge. But >> farther >> up on the bent side and in the treble I don't, neither at the belly rail. >> While I understand the idea of creating greater flexibility in the bass >> section for those low frequencies I'm wondering what the reasoning would >> be >> for thinning higher up in the scale. Also, if one is installing a >> cut-off >> bar, as I do, then were you to thin the perimeter it presents some >> questions >> about how to treat the cutoff area in the case where, as I tend to do, >> not >> cut the panel there but leave it whole. Early Steinway pianos that I >> have >> taken apart don't seem to be thinned in that area and the thinning in the >> bass section is less pronounced. David Love > > The Diaphragmatic patents are 1935 #2,051,633, and 1937 #2,070,391. Nearly > as I can tell from the patent texts, it's magic, as the descriptions don't > seem to say much that's coherent other than it increases flexibility at > the edges. > > In compression crowned boards, like Steinway's, it may improve sound > initially, but will also increase compression stress levels in the, now > thinner, panel and further shorten the life of the assembly. I see no > rational reason to thin a panel in the treble. > > For the most part, I've found it to be unnecessary if I get to put in one > of my boards. I don't use a thick high grain density panel, and can more > easily float the bass than thin it. Rebuilding with an existing board, > thinning the bass (or channeling like Overs and Seiler) can be very > worthwhile. > > Ron N > >
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