>. . I have > >yet come to a conclusion as the "why's" vs. the "how effectives" are each >>design. > >Tom Servinsky,RPT (thanks for the note in another post about Del's bridge notcher Tom) Ron N wrote; >There really isn't a simple answer either. Stiffer and heavier are >determined by width and height, like with any beam. The impedance of the >soundboard assembly at any point in the scale is determined by the mass and >stiffness of the assembly, as seen by the strings at that point. Indeed. A wider lower bridge will have higher mass with less stiffness, and vice versa. >Scale tensions, soundboard panel thickness and grain direction, rib dimensions >and placement, rim stiffness and proximity to the bridge will all have some >effect. Like everything else in a piano, everything affects everything else >in some way. Too flexible an assembly, and you get one big killer octave. >Too stiff and heavy an assembly, and you get a very quiet piano that >sustains for days. Something in the middle, and a considerable range of >something at that, is what you want. I've found that I can get enough >control of the process to produce the kind of sound I'm looking for with >panel and rib design without having to worry too much about bridge cross >sections. A couple of years ago, I replaced a 40mm wide bridge with a 30mm >wide bridge with a new soundboard and rib scale, and was very pleased with >the result. Since I haven't replaced a bridge with one of different >dimensions on the original soundboard, I can't say exactly what would happen. > >Ron N Around 1990 we re-bridged a circ. 1925 US made D with an original 8 mm crowned sound board. This piano must have been set out-of-specification originally since it had almost zero down bearing with considerable sound board crown. Since the board looked to be in good overall condition, we built new bridges (with a fully revised logarithmic-style scale) of original width but 40 mm high (standard Steinway D is nominally around 32-34 mm). No other design changes were made (speaking length and bass scale revision excepted). The result did not sound like a Steinway. It had much longer sustain with less initial sound pressure level (but nonetheless was a very satisfactory instrument). One local commentator (a tuner of note) said that we got rid of the Steinway tone to create something much more European in character. This piano was our first re-bridged D with a revised scale. The tuning stability adjacent to the plate struts was very much improved, since we altered the speaking lengths exactly to that calculated to achieve an even graduation of the percentage of breaking strain. The option of building sound board assembly stiffness with rib height, as opposed to bridge height is interesting. I suspect that bridge rigidity remains an important consideration even when stiffer sound board ribs are used to raise the impedance of a board. If tall relatively stiff ribs are used with a low height 'floppy' bridge, there is I suspect a tendency for inferior note to note sustaining qualities (the sustain will tend to be shorter for those notes which do not lay over a sound board rib - those long bridges which are attached to the sound board only over a rib at the lower end are also similarly suspect). I inspected at a new Korean made 'concert' piano last year with quite standard sized ribs and a 24 mm low bridge. The tone was, how shall I put it, most ordinary and short (most other factors seemed to be reasonably satisfactory - even the workmanship). A local contemporary manufacturer also uses 24 mm high bridges to create a 9'6" piano which sounds like an instrument from 1850 (something akin to speaking with a peg on your nose). If you look at the grand pianos from around 1850 they all seem to have lower bridges and ribs than contemporary pianos. Both these factors seem to contribute to their duck-like tonal qualities. Mind you, when listening to these instruments today with their now compression set panels, they are sure to sound even more short toned than originally. As Ron N says, "everything affects everything else in some way". It's very useful to think about each individual element and its cause and effect on tonal quality. They all come together to produce a result of some kind. There are so many combinations of stiffness, mass and radiating area which remain to be tested. As long as we can keep an open mind about future directions, superior pianos must surely be built in the future. Ron O -- Overs Pianos Sydney Australia ________________________ Web site: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au ________________________
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