Negative bearing (long)

[Richard Brekne]

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Delwin D Fandrich wrote:

>
>
>      ----- Original Message -----
>      From: Richard Brekne
>      To: pianotech@ptg.org
>      Sent: December 03, 2001 12:04 PM
>      Subject: Re: Negative bearing (long)
>       Delwin D Fandrich wrote:
>
>     >
>     > The understanding of soundboard function has
>     > moved a bit beyond the purely
>     > empirical--even beyond 90% empirical--though
>     > certainly not to the stage of
>     > pure science either. Still, techniques such as
>     > modal analysis have enabled
>     > the study of soundboard function at a level
>     > not even dreamed of even thirty
>     > or forty years ago. It is my hope that before
>     > I pass from the scene that
>     > this understanding will be still some closer
>     > to scientific and much less
>     > reliant on the empirical.
>     >
>     > Del
>
>
>      Been reading and weeding through and find much
>      that is interesting, but this comment caught my
>      eye and I must admit is confusing. I wrote about
>      modal analysis a year and a half back and you
>      came out and said it was basically useless in
>      designing soundboards, since the conditions for
>      measurement are different then the conditions
>      for full strung, and if done full strung well
>      the deed is already done so to speak... further
>      you pointed out then that you meant that there
>      was no reliable way of forcasting said changes.
>
>
>      From the fall of 1999  where we were in a
>      disscussion about impedance matching, and the
>      usefullness of modal analysis came up I submit
>      the following three posts.
>
> Pease go back and read what I wrote, to wit:
>     "One of the problems I have with most of the testing I
> have seen on the piano soundboard is that it was done on
> an unloaded board and is, therefore, largely meaningless."
>
> There is no rule that states modal analysis cannot be done
> with good results on a loaded board, complete with
> strings. It's just more difficult. Tests with unloaded
> boards are, in my opinion, largely meaningless. It becomes
> something else when done in a real world setting complete
> with strings and loading. Again, my experience is some
> limited. I have only used the technique to analyze one
> soundboard assembly and it did lead to some considered
> changes in the ribbing which--again, in my
> opinion--improved the performance of the piano involved.
>
> Del
>

Yes... I read all that...and I made that very point about
doing it on a loaded board as well, and this was also
refuted at the time.... the reason being as I stated.....
the deed was already done on a loaded board and you couldnt
change it...

I remember the discussion well... tho perhaps the varying
opinions from different folks cloudied what I thought you
all were saying at the time...

I refer you to the other postings I attached.

So... how is modal analysis then a valuable tool.... after
the fact as it were ?



--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no


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