Soundboard Crown measurement and evaluation

[Erwinspiano@aol.com]

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Terry
    Hi. you covered this one really well  & thoroughly.
   
Some pianos were designed to have negative  crown.


If the panel has an "S"-shaped cross section, it is likely  toast. That piano 
will likely have bearing on one side of the bridge and  negative bearing on 
the other - or something approaching that.
  I once bought A Steinway Long A that had  great crown in the bottom end & 
reverse crown in the top. Never seen that  since

But many other combinations of these conditions are  not necessarily bad. I 
have a Boston GP-178 that has a soundboard panel that  is as flat as a 
pancake - no crown (at least in the top half of the string  scale), but it 
has nice even moderate downbearing throughout, and the tone  is as great or 
better than any Japanese piano I have ever heard. Because it  has good 
bearing, you know that if you unstrung the piano, the soundboard  would bend 
up and you could then observe crown.
  & even if it doesn't ,so what it sounded  great. I've had many pianos that 
had marvelous sustain & power with flat  boards. Which means that the 
mechanical impedance inherent in the design was  adequate to create the sound by it 
mass & stiffness.  MY Sisters Mason  AA is like that . Awesome sound & no crown. 
The Caveat is that it had nicely  set bearing>  HMM wonder why? Grin


I will  often look closely at crown and downbearing, etc. when diagnosing a 
belly  problem, I also work very closely with all that when setting up a new 
piano  belly.
  Amen
  This is where many miss the boat. Failing to provide  adequate bearing for 
your new belly system is like having a Porsche with no gas  in the tank. amhik

However, I have found that when inspecting an  low value piano for someone - 
like for a prepurchase inspection on a 1948  Gulbranson spinet, or somesuch - 
there is usually no reason to even look at  the soundboard crown and/or 
downbearing. Who cares? What difference does it  make? If the piano sounds 
good (or as good as can be expected), the piano  sounds good, and that is 
good enough. If the piano has a bad killer octave,  who cares what is causing 
it - the piano sounds bad. A detailed analysis of  belly components often 
won't get you much in return - I usually just check  that the parts are there 
and are not falling off or cracked in half in a  situation like that.
  Right on & Happy Thanksgiving
  We have much to thank God for.
   Dale Erwin





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