[CAUT] killer octave resonator

[Andrew Anderson]

Ric,
I've been thinking about doing this to a late 90s D that is going 
weak in that range.  I'm inclined to think along lines of a soft 
assembly that is soaking up vibrational energy (the thin weak 
materialled belly rail).  I suppose stiffening this up might resist 
crown collapse a little but there is so little change in length, as 
others have pointed out, that this idea is questionable.  My theory 
leans towards stiffening the soundboard terminations against energy 
loss results in more of the energy being expended in vibrating the 
soundboard then in the belly-rail.

Andrew Anderson

At 05:14 PM 5/21/2007, you wrote:
>Hi Chris
>
>I am reasonably comfortable with how it does what it is supposed to 
>do.... at least I think I am... I just dont see how it can 
>substantially cure an already acute killer octave situation... and I 
>am not sure I see how it prevents one.
>
>The reason for this lack of understanding on my part is because I 
>have interpreted the <<killer octave syndrom>> to be equivalent with 
>a failure of the soundboard rib assembly to support downbearing at 
>the effected area.  So it seems to me that a strong enough support 
>directly under the bridge at this area is what would be needed to 
>prevent that.  I dont see how increasing the stiffness of the belly 
>rail provides that.
>
>Misunderstand me not.... I am not saying anything along the lines of 
><< I'm not a believer >>... I just wish someone would go into detail 
>to explain the relationship between a stiffer belly rail and how 
>this lessens the likelihood or degree of a case of killer octave syndrom.
>
>Perhaps my understanding of what a killer octave is to begin with 
>needs correcting..... ?
>
>As I believe I am probably not alone in a bit of head scratching 
>here.... I think it would be benificial for those who have some 
>insights into this to expound a bit on the whole matter.... both 
>exactly what the killer octave really is, its causes etc etc etc... 
>and how a stiffer belly rail relates to it.
>
>Thanks.
>
>btw... I have one of these devices... and just havent gotten so far 
>as to installing it on an appropriate instrument.
>
>Cheers
>RicB
>
>RicB,
>  I can't explain why the resonator works any more than I have. Read 
> Bob Grijalva's article in a recent PTG Journal or the instructions 
> that come with the device, from Pianotek. I will offer, however, 
> that it works PDG and if you try one one you will know that too, 
> even if you never fully explain it.
>Perhaps a quote from the instructions by Bob G could help,
>  "The challenge in desgining the Treble Resonator was enabling a 
> connection between the rim and belly rail that did not interfere 
> with the vertical bolt that extends to the plate from the treble 
> bell. As mentioned earlier (in PTG article), this vertical bolt is 
> the very reason why pianos of this type do not have a wooden beam 
> at that juncture, leaving a lengthy section of the belly rail unsupported."
>"I also wanted the adjustment to be mechanically intuitive. The 
>Treble Resonator works by pulling the rim and belly toward each 
>other through contraction of the trunbuckle, rather than expansion, 
>as in the Falcone jack design. One should rotate the tunbuckle in a 
>clockwise manner in relation to the plate that is attached to the 
>belly rail. This contraction works to reinforce and integrate the 
>entire system, possibly providing linkage betweeen the belly and the 
>rim, enabling them to expand and contract in tandem through seasonal 
>changes, rather than going their own separate ways."
>Sorry for so little science,
>Chris Solliday
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