Piano Rims ./soundboard stiffness

[Erwinspiano@AOL.COM]

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>   Del writes
> >
> > >Typically the loss of sustain time due to a low-mass,
> > >low-stiffness rim is countered by making the soundboard thicker and the
> ribs
> > >a bit stiffer. (Though ribs don't really have much effect on tone
> > >performance through the last couple of octaves in the treble.)
> 
 Phil Ford
> > Why do you say that?  Should the ribs be removed in
> > this area?  What then?  Make the board a little
> > thicker?
> 
> With the bridge so close to the belly rail the stiffness of the soundboard
> panel has much more effect on the soundboard system impedance than do the
> ribs.
>        Del
>     
>       Hi   Del
> That being the case  why is  the more modern/recent technique of using a  
> spruce rib preferred in the capo treble areas as opposed to the lighter 
> weight sugar pine version  which was original equipment?  Also if it is 
> true that the ribs don't effect impedance as much as the board stiffness 
> does then why so much weakness in the killer regions or is that the point 
> where the rib stiffness/impedance really comes into play? My thinking is 
> that right around note c- 6 must be crucial cross over point.

     It's clear from the diagram you posted that in radial version boards the 
soundboard grain and ribs don't 
> cross at right angles in the upper trebles creating greater stiffness and 
> the shorter grain angles in front of the bridge at the belly do as well 
> (due to the non traditional panel grain orientation off the belly rail ). I 
> think I'm starting to get it

   If the ribs have little to do with stiffness/impedance and tone production 
up high it would 
> seem that all this stiffening shouldn't be needed. However the feedback is 
> that the sustain is so much better in this radial board indicating that a 
> lot of extra stiffness is needed from the board and the rib to get the 
> improved sustain characteristics. Am I missing something?

         My experience is that too much stiffness can make the board a little 
stingy in the trebles including the killer region.  > I find that I personally 
> like the sound from retaining the sugar pine configuration in the capo 
> areas but crowning them from roughly a 50 ft radius graduated up to about a 
> 25 ft. On the last rib. This obviously adds some stiffness the flat ribs 
> lacked and it seems to have a good tonal balance between attack/power and 
> sustain/power balance but doesn't make it to tight sounding. I hate 
> subjective terms
>    The on going question is how stiff is stiff enough? 
>    My qustions/comments are in relation to reproducing original designs and 
> not really to redesigns all though I, m sure the principles are similar and 
> applicable.
>           I love this stuff.
>    Best--------------------------------  Dale Erwin



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