crown, +/-

Leif Olsen leifo@image.dk
Tue Apr 9 16:00 MDT 2002


Hej list

I thought about...

I have seen experienced people tapping with the palm on a soundboard ready for
restringing, claiming they could distinguish between good and bad respons.

When refitting a plate after soundboard-repair I often ask myself: is there a
crown? and only one crown? could it be negativ somewhere?

I always try to make a reasonable downbearing, but as we know every man has his
favourite digits and no concensus is near and most statements are in mm which
makes no sense to me unless a measure of the arm is supplied.

We believe that a certain relatively small downbearing on every point on the
bridges is optimum, but agree on, that zero down-bearing at a string does
not mean zero tone there and negative (or uppbearing :-) ) means a tone too on
that place (phase-shifted??) why so?

If the crown on the named instrument is inferior or negativ, then I try to
establish a decent downbearing all the same.

We intuitively know the difference between crashing an egg from the inside contra
the outside and the difference between an arched bridge contra a suspension
bridge...

My questions is this:

Is there a qualified difference in "tonal responce" from a positive to a
negative crowned soundboard, which could be explained in terms of the forces
involved?

Given the bridgepins stays in there holes and the strings don't creep up the
pins, there seems to be symmetry in the forces if we give the "negative crown
board" a "negative downbearing"?


Regards
-- 
Pianoshop Leif Olsen

Member Of D.P.I.F. Denmark

http://www.image.dk/~leifo



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