String tension (was : Birdcage pitch raise)

[Ron Nossaman]

> You answer : "I don't understand why either, because it doesn't."
> May I precise again : for a certain string with a fixed diameter in a 
> piano, when you raise it's tension, you raise it's pitch, lower it's 
> inharmonicity, and shorten it's sustain.  Agreed ?

I haven't noticed a drop in sustain, but then I wasn't looking 
for it. I'll have to try it and see. When you tune the entire 
piano as sharp as the string you tested, does the sustain come 
back? I suspect it would. I have noticed that in a freshly 
strung piano, treble sustain sounds longer after the third or 
forth pass than it does with the first or second chipping. I 
take that to mean that there is more harmonic support from the 
rest of the strings when everything is in relatively close 
tune than when most of the strings are in random counter-phase 
with the test string.


> Do I understand you that your higher trebble strings have higher tension 
> than traditionnals, because their length is longer, and that they have 
> longer sustain ... but for me, it is the extra mass of the strings that 
> is partly responsible of the sustain lengthening, together with the more 
> optimal position of the bridge on the soundboard at that place, not the 
> extra tension.  Agreed ?

Not agreed. 3mm of extra length doesn't increase mass 
substantially. It's also not the optimal positioning of the 
bridge on the soundboard, because I can't get the bridge in 
anywhere near what I think is the optimal position in the last 
section. It's the soundboard assembly mass and stiffness.


> Intuitively, an ideal string whose breaking strength was infinite, and 
> the tension you put on it infinite too, could barely move, if the rules 
> of physics still applied continuously the same way as they do in the 
> range that we observe.  The higher the tension, the lower the 
> flexibility (good for inharmonicity, bad for sustain), and the higher 
> the elasticity.
> 
> What do you think ?

I don't do intuitive infinite strength, infinite tension 
strings. The ones I work with have built in rules, and aren't 
isolated from the soundboard assembly and the rest of the 
strings. Sustain is mostly a function of the rigidity and mass 
(impedance) of the terminations in the wire length, diameter, 
and tension ranges present in pianos.


When you hear a piano, you're hearing what's left after the 
hammer and soundboard assembly have filtered and damped what 
the string is ideally capable of producing. That is, unless 
the soundboard is producing some obnoxious resonances of it's 
own, which does happen. So it's not just string tension or 
inharmonicity that is credited or faulted for the way the 
piano sounds, it's how it all works, or doesn't work, together.

Ron N