String coupling

[Ron Nossaman]

Roger, Roger, Roger,
No no no, this isn't new to you. You've known about it for years and years,
just like any tuner. You just hadn't made the connection until now.

>Traditional thinking of down bearing!!!  but we have equal and opposite
>forces at work here, the board is trying to push the strings upward with as
>much force as the strings are pushing downward.

* See there? You already have strings acting on the soundboard, and the
soundboard acting back on the strings, and you haven't even played a note
yet. You don't know your own strength, <G> and it gets even easier than
this. When you play a given note, and a damper a couple of octaves down
leaks enough that a sympathetic partial sings along, isn't that the result
of an un struck string picking up energy from the soundboard? When you hold
down the damper pedal and strike one note, isn't it considerably noisier
than when the dampers are down? Even if you stop the struck with your
finger, doesn't the sound continue while the pedal is depressed? Tada! Same
thing, the soundboard is receiving energy from the struck string and
passing it around to whatever will take it, including back to the string
from whence it came. That's what soundboards do for a living. It's what
they're designed for. Controlling where the energy goes, and at what rate,
is what gets you into the impedance puzzles, but the simple mutual energy
transfer between strings and soundboard assembly is so basic and obvious
that it's easy to overlook entirely. Forest for the trees, and all that
sort of rot.  

 When you ponder what you already know for a while, it's surprising how
many mysteries... aren't really.


>A thought came to me this afternoon, by using a Baldwin accu just piano. 
>one of the top notes in the centre section, (no forward duplex to cloud the 
>pictureadjust for minimal bearing, about 1lb down bearing pressure,measure 
>the coupling effect. Next step readjust the bearing to about 6lbs, and 
>remeasure the coupling effect.

* Interesting notion. I assume you are thinking to increase or decrease
board impedance with downbearing changes, yes? I don't see why it wouldn't
be worth trying, but I doubt if you would get any measurable difference
unless you did at least a section at a time. The bearing difference with
just one unison wouldn't appreciably change the soundboard impedance. 

See? That wasn't so tough. The plot thins.

Ron N