Rib Crowned Hamburgs ?

[Erwinspiano@aol.com]

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Del
    Thanks for the perspective but what a bout an  appropriate amount of mass 
in this area adding to the impedance qualities? I  realize the importance of 
rib stiffness for this purpose but....how much mass is  too much or not 
enough?   Too much thickness in the treble can give a  stingy sound  & too thin 
sometimes a a sound not dark enough for my  liking

Dale,
 
This is true only if the soundboard assembly is  compression-crowned where 
the thickness of the board is necessary to support  crown over the years. It's 
why diaphragmed soundboards collapse  more rapidly than do thicker  boards.

   Perhaps I'm misunderstanding your point here. Do you  mean thinner, as the 
compression load a on a thinner board would give up sooner.  Also most 
diaphramized bords are 8 mm or less around the  perimeter


 
If the soundboard is crowned using curved ribs the  bulk of the crown support 
comes from the rib and the panel functions more as a  non-structural 
diaphragm. In this system the thickness of the  soundboard is chosen based more on 
(acoustical needs  )and less on structural requirements and 8 mm is quite  
adequate. 

 

would you elaborate on  this

 
 

This is  especially true if a reasonable cutoff bar and a fish are  used.

  Yes I see this makes sense. Less area is  automatically made stiffer
   Thanks
    Dale
 


 
Del






Ron
  8 mm /.320ish is on the thin side for a 9ft grand  of any make . A board 
this thin doesn't really need much thinning. In  fact it's probably not thick 
enough in the treble. I'm unaware of the  German factory's rhetoric on panel 
thinning. I'm guessing it sounded a bit  thin? grin
  Regards
  Dale

Very  often the factory line doesn't match the actual product. How 
often  have we heard about the tapering of sound board panels from 
S&S.  They may have done it at some time but . . . The original board 
which  I pulled from a 1962 Hamburg D last year had a 8 mm thick panel  
everywhere. I still have the original panel at the  workshop.

Ron  O.




 

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