On Wed, 27 Mar 2002 11:36:14 Ron Nossaman wrote: > >The one I saw torn down a couple of years ago had the "ramped" soundboard, >"drain", and bridges super tall at the bass end. My impression was that the >cutout looked like an afterthought. I see a piano in final [sic] >development that is just too thin sounding in the low tenor. The bridge is >too close to the rim, making the assembly too stiff there. All the King's >voicers couldn't fix it, nor could an experimental scale change or fifteen. >Still sounds lousy. What to do? Shall we get new plate patterns made, new >rim presses, a clean sheet of paper and start over? Can't afford it, and >who's to say the next one would be any better? Too late at this point to >copy brand S. We're doomed! Let's go get drunk This was their mistake. They should have done this before embarking on the design. >and forget it for tonight, >we'll die tomorrow. The result looks to me like a pretty good quick and >dirty affordable post design patch incorporated into production as a >feature. You at least have to give them credit for originality and for giving the marketing department something to work with. Most other makers would have said let's go get drunk and leave it the way it is, who's going to notice anyway. > >>3. To provide some stiffness smoothing (impedance smoothing?) so that >>adjacent notes don't 'see' markedly different local stiffness in the board. > >It is, after all, a bridge. It's primary job is load distribution. >Stiffness affects assembly impedance, as is most obvious where a bridge is >notched to go under a strut, making that section of bridge below minimum >stiffness, and the tone quality of the unisons immediately on either side >of the notch are reminiscent of mini killer octaves. This lack of stiffness >is also evident at the low tenor, where the bridge (structural support) >ends, making the assembly more flexible than it is just a few notes up scale. > Ron, I pasted this bit into another e-mail and started a new thread. You can have a look if you like. >Not so. Beyond a minimum stiffness, bridge stiffness requirements aren't >(to me, at least) obviously different from one end of the scale to the >other. Assembly stiffness requirements are vastly different, and can be >dealt with by bridge placement relative to the rim, rib dimensions, etc. > You may be right. I was thinking of the bridge stiffness as part of the assembly stiffness. If you can achieve whatever assembly stiffness you want by rib and soundboard manipulation then there is no need to vary the bridge stiffness. I was thinking that at the bottom end if you made the bridge too stiff you might not be able to achieve the flexibility that you wanted even by spacing out the ribs and reducing their dimensions. At the top end perhaps it is more efficient to get assembly stiffness by adding soundboard thickness or rib height rather than bridge height since maple is heavier than spruce or pine. However, as Del has pointed out stiffening the board at the top end has more effect than stiffening the ribs. I'm not sure where the bridge fits in this picture. If stiffening the bridge has more effect than stiffening the board or ribs then perhaps it would be more efficient to add bridge height. If it's less efficient then perhaps it makes more sense to make the bridge shorter and add even more soundboard thickness. > >Whatever the reason, same height all along works fine if it fits in the piano. > That's been my observation. However, I haven't really had the chance to observe or listen to any pianos with bridges that deviated much from conventional dimensions. Perhaps they would sound even better. That's why pianos like the Mehlin are interesting, even though I didn't hold out much hope that it would be a shining example of what could be achieved by unconventional design. > > >>5. To change the vibrational response (mode shapes) of the board. I don't >>know >>what the optimum dimensions would be for this but it seems likely that to get >>whatever response the designer decided he wanted he might have to use a bridge >>that had different stiffness and mass along its length. > >Of all the folks who have designed, built, and installed soundboard >assemblies, what do you suppose is the percentage who have ever seen the >modal patterns of the boards they've built? Few, I imagine. >And of that percentage, who >among them can anticipate any given resulting modal pattern from the CAD >drawing or sketch? Fewer still, I would guess. >It's a lovely concept, and a potentially valuable >forensic tool, but it would sure surprise me to find there was any use at >all for it in the design process. There may never be a place for it in practical design, but I'm not giving up hope yet. >Optimal, also, depends on what you're >after, doesn't it? Right. > > > >>6. To give an observed result. Perhaps if you built several pianos of >>similar design >>with different bridge heights you might decide you liked the top end of the >>piano with >>certain bridge dimensions and the bottom end of the piano with other bridge >>dimensions. This might lead you to think that your optimum bridge was one >with >>varying dimensions from top end to bottom end. > >Or that your hammer sets were slightly different, or your panels were of >slightly different densities and stiffness, or your ribs were slightly >stiffer in one than the other, etc. There are some (sometimes major) tonal >differences from piano to piano of identical design, and sequential serial >numbers. With a two piano sampling, we can lead ourselves to believe an >extraordinary number of things. > Agreed. Which is why I carefully chose the words 'might lead you to think' rather than 'shows' or 'demonstrates'. Control is always a problem when trying to compare two complicated things with lots of variables. It's usually almost impossible to change only one variable at a time. So drawing conclusions is a dicey proposition. However, it's really the only method we have. If we give up on it, we have no way of drawing any conclusions or making any meaningful changes. > >As long as it's designed and built without compromise. > >Ron N > With no expense spared. Phil F See Dave Matthews Band live or win a signed guitar http://r.lycos.com/r/bmgfly_mail_dmb/http://win.ipromotions.com/lycos_020201/splash.asp
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