On Mon, 25 Mar 2002 23:35:17 Delwin D Fandrich wrote: > >> The way I remember it was the area between the last rib (most >> bass-wise rib) and the rim was open. Also the soundboard was set into the >case >> at an angle so that the bridge was quite a bit taller at the bass end than >at the >> treble end. I seem to recall it had some sort of fanciful name like >cello-piano or >> cello-tone or some such thing. I only saw the piano when it was destrung >and >> never got to hear or play it. > >Odd. I don't remember this about the piano. It seems the soundboard was >installed in a more-or-less conventional manner. It's been some time since I saw this, so I may not have it quite right. But, Conrad says he works on a similar piano, so I guess I haven't completely lost my mind. I do remember the opening in the board and the fact that the bridge was quite a bit taller at the bass end. It could be that the soundboard was level and the plate was set in at an angle, but that's not the way I remember it. > >And why would the 'optimum' bridge height vary from one end to the other? >Indeed, what is the 'optimum' bridge height? The added mass of the taller >bridge isn't going to make much, if any, difference. And, beyond a certain >point, neither will any added stiffness. > >Del > > Optimum is, as ever I suppose, in the eye or ear (or mind) of the beholder. It would depend on what you believe the purpose of the bridge is and how the string, bridge, soundboard systems operates. Some of the possibilities that I have heard, or some that I just made up myself: 1. To provide a 'path' for the vibrations imparted at any one spot to 'travel' to all parts of the board. If this is the function then what are the optimum dimensions? Is it dependent on frequency? I don't know. 2. To provide something solid to drive the bridge pins into. If this is the main function then the bridge really only needs to be big enough to hold the pins. Any extra material would be superfluous. How long do the pins need to be anyway? Probably not as long as they commonly are. Anything much below the surface of the bridge is probably not doing much. So practically speaking, the bridge could be very short if this were its only function. 3. To provide some stiffness smoothing (impedance smoothing?) so that adjacent notes don't 'see' markedly different local stiffness in the board. If there were no bridge or a very short bridge, the notes that attach to the soundboard directly over a rib would see more local stiffness than a note that attaches to the soundboard between ribs. This seems to me to assume that the forces applied to the board by the vibrating string (and the subsequent board movement) are important to the production of sound. As discussions here have shown, this is a topic of debate. But assuming that this is the function of the bridge what is the optimum height? Since the strings at the low end of the scale have more excursion and usually higher tension then the forces they are applying to the bridge as they vibrate are greater. So it would seem that you would need more bridge stiffness to provide this 'smoothing'. This could mean a taller bridge at the bass end. 4. To provide stiffness to the soundboard, rib, bridge system in addition to that provided by the board itself and by the addition of ribs to the board. If this is the primary function then it seems you would want more stiffness at the top end and less stiffness at the low end. So the bridge might be taller at the top end. Perhaps items 3 and 4 balance each other out so that the bridge should be the same height all along. 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. 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. 7. To serve as a marketing tool. As with soundboards and other things I won't mention bigger must be better, right? The sales people can say that your piano is better than the competition because it has a bigger bridge. Or they can say it has a more high tech design than the competition because the bridge changes dimension and is 'optimized' throughout the scale. It has Patented Acoustic Construction as one manufacturer says (or used to say). Phil F 2,000,000,000 Web Pages--you only need 1. Save time with My Lycos. http://my.lycos.com
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