Killer Octave & Pitch Raise

[Michael Gamble]

Hello Ric
Interesting post - and one which affects all who undertake the restringing 
of pianos. In order to comply with the best proceedures with relation to 
bringing a piano down to remove the old strings - and, more importantly??, 
bringing the piano back to A=440 what, in the interests of your post, do you 
believe to be the best course of attack? Please take it step-by-step if you 
would be so kindly! So you're face with restringing an S&S model D........go 
from there!
Regards
Michael G (UK)
----- Original Message ----- 
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: "Newtonburg" <pianotech@ptg.org>
Sent: Saturday, February 12, 2005 12:54 AM
Subject: re: Killer Octave & Pitch Raise


> Udo Steingræber and I got into a conversation about this in Helsinki a 
> couple years back on the only opportunity I've had to sit and chat with 
> him.  It was part of a discussion where he was explaining why he felt 
> compression soundboards were the way to go.  He mentioned something about 
> the so called K point (I think this is a Klaus Fenner coined term), which 
> as I understood it was that point on the soundboard where crown from both 
> along the grain and cross the grain intersect and is at its highest point. 
> This area is exactly (and always) in the area typically refered to by 
> american techs as the <<killer octave>> area, and of course varies 
> somewhat from piano to piano.  It is then  also the exact point then that 
> is most vunerable to failures.  Udo was of the position that along the 
> grain crowning was every bit as important as cross grain crown.  Something 
> to do with along the grain compression due to downbearing having a 
> stablizing effect on cross grain crown and strength.  He also meant that 
> both these were needed to produce the kind of acoustical results he wanted 
> from a soundboard.
> I'm under the impression, correct me if I am wrong, that most of the rib 
> crowned methods extoled on this list do not employ any purposefull along 
> the grain crowning as part of how the panels are attached to the rim, and 
> therefor do not have this vunerablity.  It would stand to reason that they 
> too are not able to create the same acoustical  results.... (whether that 
> is preferable or not is an entirely different subject).
>
> Disclaimer.  This description is my understanding of what Udo was saying, 
> tho I beleive it is pretty accurate. Not being a soundboard engineer tho, 
> I'll leave it to more experienced to explain, interpret, or whathave you 
> the above.
> One other thing tho... I've always heard that large changes in pitch, and 
> destringing / restringing proceedures should be carefull of this area.... 
> making carefull changes that are appliled very evenly,  exactly because 
> this area can easily be damaged by sudden large changes in the stresses 
> applied to the panel as a whole.  Seems to jive well if the basic view 
> above  is correct to begin with.
>
> Cheers
> RicB
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