Since my general protocol on rebuilds using original boards (Steinways anyway) is to recap the capo section which often involves increasing the bridge height, I have generally noticed (though very unscientifically) some gain. It wasn't clear to me whether that was simply due to rescaling that section (I usually increase the tensions somewhat as they are often a bit low--especially on the smaller grands), improved terminations, or, as we are discussing, an increase in stiffness, as you have pointed out. Since adding stiffness is the usual goal on older soundboard killer octaves, what, if any, would be a reason to not do this generally? What sort of increase in bridge height would be needed to effect a change in stiffness in that section and what do you think might be the point of diminishing returns and what would those be? Something to ponder while gnawing on that turkey leg. Or am I just full of stuffing? David Love davidlovepianos at comcast.net www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman Sent: Wednesday, November 21, 2007 4:51 PM To: College and University Technicians Cc: 'Pianotech List' Subject: Re: [CAUT] Soundboard mass > Anyway, I'm wondering if others have done similar things with similar > outcomes or found that bridges below a certain height simply don't have > enough mass without some help. Further, with a certain minimum bridge > height does mass loading become unnecessary? I think it's stiffness, rather than mass that makes the most difference in the taller treble bridge. Addition of mass doesn't typically do much good for the classic killer octave, but mass loading a treble that is too stiff and screaming wild with short sustain helps considerably. It's a resonant frequency thing. http://www.kettering.edu/~drussell/Demos/SHO/mass-force.html >I've often wondered if the > early Steinways with bridges under 30 mm in the treble (and sometimes well > under) don't compromise those areas by virtue of inadequate height and > therefore both mass and stiffness to begin with. I'd say so. That and the compression crowned boards. > Moreover, is there what one would consider an ideal bridge height? You can get away with a shorter bridge with more ribs, where fewer ribs need the added stiffness of a taller bridge. One of those "it depends" sort of things - again. Assembly stiffness, mass, and frequency response requirements are the thing, and variations on proportion among the assembly's parts can average out similarly in practice. The rules are different, naturally, in different parts of the scale. > BTW Ronsen Bacon hammers with plenty of power (after a more refined filing > in the treble) and warmth! No lacquer, no plastic! MMMMMMMMMMMMMMMmmmmmmmmmmmm, yea. Ron N
This PTG archive page provided courtesy of Moy Piano Service, LLC