S&S D Duplex

[Stephen Birkett]

In his patent, Theodore Steinway indicates a quite different function for 
the front and rear duplexes (or should we say duplices). His motivation for 
the front duplex section is to prevent string breakage at the agraffe by 
allowing the string to vibrate on both sides. He then suggests that the 
section should be tuned to a harmonic of the main speaking length to 
enhance the tone. But this seems to have been a secondary consideration, 
and not the primary reason for the front duplex. As for the rear duplex he 
notes that transverse vibrations will not pass the bridge termination, on 
account of its rigidity. However, he notes that longitudinal vibrations 
will pass the bridge, and designs the rear duplex section to provide a 
multiple of 1/2 speaking length behind to bridge. To paraphrase his 
reasoning, this will bring the longitudinal whistling noises into better 
harmony with the string fundamental. [not passing comment on the validity 
of his argument here - that is a different story - only your dog will be 
able to tell for much of the scale].

So, to summarize CFT's reasoning in the patent: FRONT the primary function 
of the front duplex is to prevent string breakage, but, once it's there, he 
recommends tuning the front duplex section to enhance the tone by harmonIc 
transverse vibrations. REAR the only function of the rear duplex is to 
eliminate non-harmonic whistling by tuning a longitudinal mode. In this 
patent, then, both duplices were intended by CFT to be tuned.

Hmmm. The patent is quite specific on these points.

Stephen

Stephen Birkett Fortepianos
Authentic Reproductions of 18th and 19th Century Pianos
464 Winchester Drive
Waterloo, Ontario
Canada N2T 1K5
tel: 519-885-2228
mailto: sbirkett[at]real.uwaterloo.ca
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