Of Miracles and Duplex's (was Re: S&S D Duplex)

[Bill Ballard]

At 1:42 AM +0100 11/25/02, Richard Brekne wrote:
>If the duples is such a fantastic (as in unbelievable) idea, why is 
>is so easy to buy into the idea that slightly out of tune unisons 
>give longer sustain then clean or far out of tune unisons ?Its all 
>about ever so slightly assynchrohnous vibratory reonforcement :)

Maybe that's another issue to put to the test. I haven't heard it. 
(I've heard the decay of unisons disguised by a very slow roll.) But 
we should remember that the only energy existing in the system is 
that delivered by the hammer. Good design can increase the efficiency 
of energy use. But nothing new is created.

You can either spend all that energy in a brief flash or taper it out 
over a long interval. Sustain necessarily reduces volume; it's a 
trade. (If I'm wrong Del will chime in..) I would tend to assume that 
if we made it too easy for energy arriving at the bridge to move 
straight on in a harmonic rear duplex length that we would be 
shunting energy which couldn't later be retrieved, and should have 
gone to the board. Oh, we would have heard that duplex singing 
alright (even if it happened to have the right speaking length but 
was five strings down). It's just that the board is a much better 
speaker mechanism than music wire.

Where is the magic in the tuned duplex section? Is the expected 
increase in sustain we're expected hear simply because the rear 
duplex happens to add its own reflected sound, as with a sympathetic 
vibration? Or is there something about the consonance of the 
wavelengths on either side of the bridge which actually decreases the 
rate at which the bridge absorbs energy from the speaking length of 
the string. Once again the only reason anything exists in the RDLs is 
because the SL's energy went there instead of into the board.

Bill Ballard RPT
NH Chapter, P.T.G.

"No one builds the *perfect* piano, you can only remove the obstacles 
to that perfection during the building."
     ...........LaRoy Edwards, Yamaha International Corp
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