David,
Paul H. Bilhuber patented the diaphragmatic board in 1936 for Steinway. To my knowledge, they still do it. I don't have enough knowledge of RC&S boards to comment on the virtues of thinning. When rebuilding, I played with thinning and not thinning on CC boards and found thinning advantageous. I thin the boards on both our models as you describe. On the advise of a colleague, I carried the thinning up through the treble curve on the new 275 we're building (I'll let you know how it works out). The idea being that although the treble should be stiffer, it still needs to move and have good "spring effect". Our 275 board is 10mm and I thin to around 6mm. The 220 board is 8mm and I thin to around 5mm in the bass corner with good results. We don't thin on the cut-off bar area. Fazioli does a similar thinning process with a 10mm panel being thinned to 6mm. At Steingraeber, they put fine sand on the bellied board and thin areas where the sand collects while pounding on the board. This is reminiscent of the era of "soundboard sculpting" where techs were thinning only specific areas of the board (based somehow on "sound", but I don't know the specifics) as opposed to a general smooth taper.
I would also enjoy hearing theories from Del Fandrich, Ron Overs, Nick Gravagne and other "heavy weights". Any takers??
Michael Spreeman www.RavenscroftPianos.com
> From: davidlovepianos at comcast.net> To: pianotech at ptg.org> Date: Sun, 25 Jan 2009 08:28:20 -0800> 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> www.davidlovepianos.com> > -----Original Message-----> From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf> Of V T> Sent: Saturday, January 24, 2009 9:17 PM> To: pianotech at ptg.org> Subject: [pianotech] Diaphragmizing> > > Hi David,> > Darrell Fandrich used to do that on some of his pianos. Perhaps, he would> share some of his experience and knowledge.> > Vladan> > >Can anyone speak to the history, philosophy, current practice and general> >effect in different parts of the piano of thinning soundboards around the> >edges also known as diaphragmizing? > >> >David Love> > > > >
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