Bridge caps

[Ron Nossaman]

Hi Paul,
I'm late getting back here, but for the last month, Cox hasn't been able to
keep the mail server working for 48 hours straight, and I had to wait for
this to appear in the archives to find out what the server ate. 


> Why, then, does a bridge pinned 
>shallowly, or a bridge pinned into a cap that is too thick not reaching the 
>bridge trunk, have entirely different tonal characteristics from a bridge 
>pinned into the trunk deeply. This is audible and certainly measurable with 
>the proper tools; its audibility is not intuition or invention on my part; 
>what accounts for it then? 

Perhaps so. I've not been able to verify it, but then I haven't done a
piano with lot of different pin heights evenly interspersed along the scale
to specifically test it and establish audibility thresholds.  


>Is bridge pinning just a traditional way of 
>securing the string over the bridge harking back centuries and having no 
>other physical purpose than you purport? 

Yes, I think so. If the early experimenters had found a better way that was
as easy and cheap, they would have used it instead. Had they found an
easier and cheaper way that was just as good, they would have used that.
What we see now in bridge pinning is just the expedient compromise between
performance, ease of production, and cost. But I wasn't there when these
decisions were made, so I can't say for sure. It's a moot point anyway,
because we're talking about energy leakage from overly tall and not
bottomed out pins. 


>You say that you can see no other 
>reason; is argument by the claiming the absence of positive proof a positive 
>argument? Is this just a bit too legalistic? 

Come on now, how legalistic is it to dodge my examples and attempts at
explanation by diverting attention from content to method? This isn't
personal you know, it's a technical discussion, and I'm trying to find out
what you're basing your claims on.


> How do you 
>know, in the absence of other information, that there is NOT energy transfer 
>through the pin? 

Of course there's energy transfer through the pin. The pin clamps the
string to the bridge and the VAST majority of the energy transfer occurs at
the point where the pin is itself clamped in the bridge, not at the bottom
of the pin far beyond the clamp point. That not only seems thoroughly
logical and obvious to me, it's intuitive too. 




>Since either speculation is devoid of hard proof, then 
>either may be right. MY intuition is that vibrational energy is passing down 
>the length of the pin to whatever depth it goes through whatever material it 
>goes through at whatever grain orientation of that material with whatever 
>efficiency and with whatever impedance effects. Miniscule defined or 
>undefined; audible, uncontrovertible. 

Discernable affect is the point here. 


>Pull a pin (or better, drive a pin just 
>to that point where it is doing its mechanical thing holding the string in 
>place and listen to the tonal characteristics; drive it a bit deeper and 
>listen again, etc. I hear a difference. Really I do; I'm not making it up. I 
>hope that this isn't one of those things that'll appear in the Journal of 
>Irreproducible Results. 

Now I didn't say you were making it up. I was questioning your assumption
of what caused the effect you heard. At what depth is the pin doing it's
mechanical thing? There's the rub. Can you hear the difference between 5mm
deep, and 8mm deep? How about the difference between 20 and 22mm? At what
point does it cease to make a discernable difference? Also, did you try
different length pins driven to the same height to test the idea that
energy leaks off the top of a pin left too high? How about a pin firmly
bottomed out in a hole 15mm deep, next to one driven 15mm into a much
deeper hole? Seems like that would be a pretty good way to separate the
hole bottoming from the top leakage for a quick cheap test. Still lots of
variables.


Ron N