[CAUT] Lack of low-frequency response

[Richard Brekne]

Hi RA...  Ron's been tossing me some sound advice off and on for several 
years now... and he's a big part of why I'm on this track... and it 
seems to jive well with what Wogram has to say.  I'll poke around for 
what Schimmel did... but I know they dropped their RC&S attempts in 
favour of their previous more CC based approach.  Perhaps if one of our 
Rons, or Del had had a hand things may have turned out different... 
Still Europe is conservative in this respect.

As for retro-ing Zimmerman and the like... I suppose much depends on how 
well you can access the underside of the panel.  If you need more 
stiffness in a specific area of the panel there may be ways of getting 
there... depending on what exactly what kind of stiffness requirements 
are needed I suppose.

On the instrument I am dealing with at hand I will be stringing down 
again to correct a few things I've missed on a bit.  And I will be using 
the opportunity to spread some glitter on the thing and see where it 
gathers when I bang on the tenor bridge.  I'll sand if I think its 
necessary.  Dimensions of the panel and rib structure are already taken 
so thats not a problem.  And we are going to install some diagnostic 
reversible cross grain stiffening devices to see if what happens.  If it 
looks good... either rib capping or additional ribs will be retrofited.  
Its not worth my time financially no... but most definitely worth it in 
terms of what I am learning.

Cheers, and thanks for the input.  There is a lot of potential value 
here... at least for my part.  If it turns out that a lack of 
appropriate compensation for anisotropism can cause this lack of bass 
response.... then there are some questions that need answering.  Like 
for instance where does the needed cross grain stiffness in CC boards 
with ribs of insufficient dimensions in themselves to yeild said 
stiffness come from ?  My intuition says the panels compression itself 
must be the answer... what else is there ? And if thats so... well the 
whole CC, RC, RC&S discussion takes on a new dimension I think.  One 
with new pluses and minuses on both sides.

Cheers
RicB


    Check out what Ron Overs does to the soundboards for grands he
    re-manufactures from Asia...
     
    http://overspianos.com.au/OS003.html
     
    Also, a few years ago Schimmel did research, and came up with their
     
    "Schimmel resonance system"
    Diaphragmatic cross section of soundboard**
    Soundboard tri-dimensionally crowned
    Strong ribs for excellent energy distribution
    One sound reflection bar
     
    See if you can find more info on this process....
     
    This would be hard to "retro" into a pre-existing Zimmerman, but
    I'll bet you could use violin planes
    to do this. (Check out the violin planing methods, i.e. tapping, and
    transducer tones)
     
     Are you proposing to remove the strings/plate, and work on the
    board in the piano?
     
    How will you modify the ribs to make them stiffer,if that's the
    problem? Is the back
    open enough to get them in there? What about the added weight and mass?
    Perhaps you could "cap" them ala Overs. (See his website for those
    I-beam ribs).
     
     Well, I had one customer with this tiny (tinney) Zimmerman grand,
    and the sustain was very short,
    and very shallow bass, many, many false beats, etc. It's my only
    experience w/Zimmerman. (4'10")
    I wouldn't expect it to have much bass, and it doesn't.
     
    I think you need to take many soundboard and rib thickness
    measurments over the board and see just what kind of board set up
    you have there. Maybe Ron Overs or one of the other piano designers
    could help you
    out. I would wonder if it is worth your time financially, as you'd
    not get much out of these in resale.
     
    good luck Ric,

 
RA
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