rim laminations

[Ron Nossaman]

>Concerning the material used for inner rim laminations, I wonder how 
>critical it  really is tonally.  The inner rim, of course, has several 
>functions -- 1) to provide an immovable surround the for the framing (back 
>or Rast) into which the braces can be securely dovetailed, 2) to provide a 
>solid medium into which the string-plate bolts can be screwed, 3) to add 
>rigidity to the outer rim when this is glued on and 4) to provide, at its 
>outer edges only, and in combination with the outer rim, a massive and 
>solid frame for the soundboard.

Hi John,
Something between the string and the ear has to be stiff or the piano will
dump all it's string energy at once and sound like a banjo. A thicker and
stiffer soundboard will somewhat compensate for lack of stiffness in the
rim, as will a stiffer bridge. The tradeoff for the increased sustain
achieved is a loss of volume, so you go to a heavier and harder hammer to
jack it up. That effectively eliminates the low end of the dynamic range
and sells a lot of ear plugs to tuners, but you now have volume and sustain
- if not musicality. You also get pianos that are very dependably uniform
from instrument to instrument since the subtleties of the material
properties are overpowered in the brute force approach. A stiff and massive
rim, on the other hand, doesn't absorb and damp the soundboard's energy as
rapidly as a less stiff and massive rim (though it obviously will to some
degree no matter how stiff and massive it is), and lets you use a lighter
and more responsive soundboard assembly, which lets you use a softer, more
resilient hammer and get a broader dynamic range while still having good
volume and sustain. There are probably a near infinite combination of
stiffness/mass combinations in various component parts of the system that
would produce a sound someone would buy.  

My assumption with that Yamaha rim I mentioned was that it was intended to
stiffen the rim assembly somewhat and still be easier to bend and possible
to produce in a short cycle production process than an all maple rim.
That's why I asked, to see if anyone could verify or correct my assumption.


Ron N