Cases and rims, ash and such...

[Delwin D Fandrich]

> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
> Behalf Of gordon stelter
> Sent: April 09, 2004 4:54 PM
> To: Pianotech
> Subject: Cases and rims, ash and such...
>
>
>
> > > And SOME energy escapes the
> > > soundboard via the rim-to-board glue joint,
> >
> > Is much lost to a good glue joint? Maybe if it were
> > falling apart.
>
> Au contraire, mon frere! The better the joint, the
> more is lost due to transmission through the glue.

If you have any kind of proof for this I'd sure like to see it.


>
> BUT, I do suspect that a board which is flexed near
> the rim due to crown and a  proper rast-to-board
> contour relationship will reflect more energy back to
> the board, as a slight node is created in the stressed
> "kink" at this juncture.

Again, if you have any kind of proof for this I'd sure like to see it. In
both cases even a good theory would be interesting.


> >
> > > then travels around the rim wood to re-enter the soundboard
> > > at another point than its preferred point of entry, the bridge.
> >
> > Now this is sounding like a marketing brochure with
> > 8X10 color glossy photos with circles and arrows and
> > a paragraph on the back of each one.
>
> So what? Perhaps it is so!  Put a  tuning fork on a
> piano leg and you will hear the board resonate. Play a
> note and you can feel the case vibrate with your
> fingers. Granted, recycling truant vibrations is not
> the primary means of sound production, but it is
> better that these vibrations get another chance to be
> transformed into sound than that they get dissipated
> by heat in a cheap, soft rim or case. Ever tuned one
> of those Yamaha uprights with  a particle board case?
> They sound awfully "thuddy" to me!

Well, if you put a tuning fork on the leg of a table saw you will also hear
things resonate. None of this supports any kind of theory that wave energy
lost to the rim recycles through it and back to the soundboard.


>
>      Now, compare that with one of our admired Knabes
> from the late 19th century. These pianos have a  very
> "hard", distinct tone. Why? In my opinion, it is
> because the ash/rosewood/ebony rims and cases do not
> dampen the higher harmonics of vibrational energy as
> it escapes the soundboard into the rim and case, and
> then transfers it, partially, back into the board.

Most energy that gets into the rim is damped. Very little is radiated to the
air as sound energy. All wood has internal resistance. It is this resistance
that dampens the wave energy that is coupled to it from the soundboard. It's
a loss, loss situation.


> >
> > > be absorbed by it and transmuted into heat. So the
> > > cases were of hardwoods. And I am sure that you will
> > > agree that these pianos have a vital, "stirring" quality to their
sound,
> > > lacking in other pianos.
> >
> > Yeah, so they had massive hard-hardwood rims that
> > effectively terminated the soundboard and tended to
> > not dampen the soundboard.
>
> In my opinion they either deflected or accepted and
> transmitted the vibrations, but they did not absorb
> them. Deflection is best. Transmission is next best.
> Absorption is no good ( see particle board case,
> above. )
>
> Do little vibrations
> > really travel 'round and 'round and re-enter a
> > soundboard?
>
> Some, yes. I am certain of this.

Based on what? Yes, you feel the rim vibrating as the piano is being played.
That is because energy is continuously being fed to it from the soundboard.
Most of the energy lost into the rim is lost there due to the internal
resistance of the wood. Some very small fraction is transduced to the air as
sound.


> >
> > >     You said that you liked pianos with ash beams.
> > So do I. And the beams were built of ash because.......???
> >
> > I think I said I have a couple pianos with massive
> > ash rims. Haven't seen too many ash beams/braces,
> > although I can't imagine why ash would not make for
> > a good beam. I think ash makes for a good rim
> > because it is hard and massive, much like hard
> > maple.

And on this we agree. Plus it bends nicely.

Del