Rear Duplex... very long...

[Ron Nossaman]

Hi Brian,

 ------------------------------------------------------------------
[   Perhaps the perception of best is in the ear of the listener?  ]
 ------------------------------------------------------------------

(That's a frame)


>It would seem logical to me that the pianos with aliquots, either fixed or
>movable, single or bar type, were intended to allow that back section of
>string length to speak.  (Perhaps this is where the term rear duplex came
>about.) Just what this adds to the overall tone production / projection
>could be the topic of a very long book.  Some appear to have been designed
>to speak at random, and others appear to have been designed to speak at a
>particular harmonic of the speaking length.

* Correct, the idea in the apparently random length duplex, I think, is that
some duplex segment, somewhere on the bridge, will sympathetically respond
to whatever is played. The tuned duplex is an attempt to match the speaking
length of each note, with an appropriately tuned segment on the back scale
of the same note. I'm not convinced that this is particularly beneficial,
since the duplex segment of any given note doesn't get it's energy directly
from the speaking segment of the same note anyway (like the front duplex
does), but rather all the duplex segments get their energy second hand, from
bridge movement. The rear duplex can add enough sound to make an aurally
detectable difference, not only on the low tenor, where, like you pointed
out, it is often muted, but up through the treble too. Because there isn't
any direct energy bleed through, rear duplexes aren't normally loud enough
to be problematic, whatever termination system is used.  


>Some examples...
>
>On newer Baldwin pianos, the string comes off of the back bridge pin
>straight back to the hitch pin.  I do not know if these lengths were
>actually designed to speak or not, but they do, at least to some extent.
>There is not nearly so precise a termination point at the hitch pin
>(vertical) but those segments do kind of speak in a random type fashion.

* The best part about this termination system is the pivoting action of the
string loop on the hitch pin, rather than the flexing of a string over an
aliquot. With the nice long backscale lengths, it's a very un-restrictive
system. I'm a dedicated fan of this type of setup.


>On most Steinways, there's a setup with an aliquot bar which on some you'll
>find sort of 'tuned', and on some you'll find not in any particular tune at
>all.

* And I'm not sure it really matters.



>Two things come to mind as 'concerns' of backscale design, which I really
>don't have specific answers to.  1) I would think that a backscale of any
>kind should be of sufficient length so as not to 'clamp' the natural
>movement of the soundboard oscillation.  

* Very important, much more so than duplex type, from my observations.


> And 2), I would
>suspect that there would be those who would argue that having a rear duplex
>tuned either to the same frequency, or to a partial of the frequency of the
>speaking length of the string, could bleed off energy from the speaking
>length, and have a detrimental effect upon the tone produced.  In light of
>the physics of the thing, if the energy is bled from one speaking segment to
>another speaking segment, have we really lost significant sound energy?  I
>don't know?  I'm asking?

* Interesting, I don't recall this one ever coming up before. Again, since
the rear duplex is powered second hand by general bridge movement instead of
straight bleed through, it is going to move whenever any note anywhere in
the piano is played, whether it's in tune with anything or not. As long as
the duplex segments are long enough not to restrict bridge and soundboard
movement, I don't see how it could be a factor either way.



>Where does it lead?  Well, if everyone was in agreement as to which system
>is best, I would suppose they would all be the same. 

* Only if it made a really dramatic and unmistakable difference. If you
really can't hear an appreciable difference there isn't any incentive to
change, and each manufacturer's system can easily be made to be the "best"
by application of a little specific advertising. It's much easier than R&D
anyway.



>It is indeed an interesting topic, and one that is probably all too often
>neglected to speak of greater things such as crown and downbearing.  ;-)

>Brian Trout


* It all counts. Well... everything but Naugahyde Wurlitzers, anyway.
 Ron N