S&S D Duplex

[Farrell]

> 5.  If, as you say, only your dog will be able to tell over much of the scale,
> why does Steinway choose to put them only in that part of the scale where your
> dog would be able to tell?

Same reason you find a rear spoiler on a 115 hp Honda automobile. It doesn't make 'em go any faster, but rather it makes them sell faster.

Terry Farrell
  
----- Original Message ----- 
From: "Phillip Ford" <fordpiano@earthlink.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Sunday, November 17, 2002 1:24 PM
Subject: Re: S&S D Duplex


> On Sun, 17 Nov 2002 00:56:12 -0500 Stephen Birkett
> <sbirkett@real.uwaterloo.ca> wrote:
> 
> > In his patent, Theodore Steinway indicates a
> > quite different function for 
> > the front and rear duplexes (or should we say
> > duplices)....
> 
> > 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 ...
> > ...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,
> We've been over a lot of this in the not too distant past.  But, at the risk
> of repeating what may already be in the archives, I'll make a few comments.
> 
> 1.  Steinway's current building practice (and the practice for many decades)
> is to define the length of the front duplex by the plate casting.  Since this
> is not tunable, they are at odds with their own patent.  You might say that
> they are 'pre-tuned' if you precisely controlled the plate casting and
> precisely controlled the speaking lengths of the strings by plate and bridge
> placement.  But neither of these things is the case, especially not at
> Steinway.
> 
> 2.  CFT seems pretty clear that he intends the rear duplex to deal with
> longitudinal vibrations, not transverse vibrations.  If I am not mistaken, the
> people who are talking about tuning the rear duplex are talking about moving
> the aliquot to make the back scale length such that its TRANSVERSE vibration
> is a harmonic of that of the speaking length.  Once again, this seems to be at
> odds with the sacred patent.  One could make an argument that doing this type
> of tuning is a good idea and will yield positive results, but it seems to me
> that one would not be justified in using this patent as beatification of that
> practice.
> 
> 3.  If longitudinal vibrations can pass the bridge, it seems to me that they
> can just as easily pass the aliquot.  So the aliquot position is irrelevant.
> The plate pin becomes the relevant thing. In order to actually tune this
> portion of the string for longitudinal vibrations you would need to have a
> movable plate pin.  This feature has not been incorporated into any piano that
> I have seen.
> 
> 4.  Assuming that you could tune this portion of the string for longitudinal
> vibration, how do you go about tuning something that only your dog can hear? 
> And, assuming that we now have machines that could hear this for us, how did
> they go about doing this back in CFT's day?
> 
> 5.  If, as you say, only your dog will be able to tell over much of the scale,
> why does Steinway choose to put them only in that part of the scale where your
> dog would be able to tell?
> 
> Phil F
> 
> 
> Phillip Ford
> Piano Service & Restoration
> 1777 Yosemite Ave - 215
> San Francisco, CA  94124
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