Piano Rims ./soundboard stiffness

[Erwinspiano@AOL.COM]

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In a message dated 12/30/2001 7:34:18 PM Pacific Standard Time, Erwinspiano 
writes:


> Subj:Re: Piano Rims ./soundboard stiffness
> Date:12/30/2001 7:34:18 PM Pacific Standard Time
> From:<A HREF="mailto:Erwinspiano">Erwinspiano</A>
> To:<A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A>
> 
> 
> 
> .
> 
> >>  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 
>> 
> 
>     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 ). 
>> 
> 
>   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 
>> 
> 
>         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--------------------------------  
> 



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