Rear Duplex... very long...

[Richard Brekne]

Brian Trout wrote:

> Hello Richard,
>
> I couldn't resist giving my two cents on the subject, although I'm sure
> there are others out there who are much more knowledgeable.

Your "two cents worth" are always welcome my freind... and you understate their
value

>
> It appears that there has been a lot of experimenting going on over the last
> century as to what is best.  Perhaps the perception of best is in the ear of
> the listener.?

nicely put

> 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.
>
> On many pianos, the lower portion of the backscale is muted, as the lower
> sections tend to give off tones that people can find pretty objectionable at
> times, but on most of the designs I've seen, the upper two sections are
> usually the ones set up to 'sing'.

One thing I have noticed... is that even on pianos where plucking the backlength
results in a pretty strong tone... muting this length while striking the hammer
for that note makes no real noticible difference in the sound. At least not like
doing the same for an active front duplex.  Rons point about the bridge giveing
the length its energy "second hand"  kinda makes me scratch my head even more.
Seems like its not really duplex at all, but rather more important in regards to
what you say below.

>
> 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.  I'm thinking that having a duplex
> scale laid out that was too close to the rear bridge pins could have an
> adverse affect upon the soundboard's freedom to move. (Similar thought as
> having the hitch pins too close to the rear bridge pins.)  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?

I have heard this about the front duplex. My own experience is that tuning the
front duplex to non harmonic intervals with the fundemental alleviates what i
call a "steam whistling" kinda noise coming from a front duplex. You can get two
(at least)  kinds of front (very active) duplexes, one that sounds really
whistelish, and one that creates a kinda clear bell like sound. I find that
makeing sure the front is like around a 9th, an octave and a 3rd or 6th, or two
octaves and a 3rd or 6th work pretty well, sometimes even something between a
2nd and a minor 3rd works in the really short strings. But on the backlength I
never run into this problem, just doesnt seem to be enough of the "duplex
effect" there. Ergo my question. I am wondering if the nature of the bridge's
termination of the speaking lenght simply excludes this kind of duplex effect
and if so, why then is it called a duplex ?

>
>
> On a less technical note, it's a beautiful day here in S.E. Pennsylvania.  I
> hope you all are enjoying your part of the world as well.

We have had the warmest September in history here.. and one of the busiest in
the piano business in memory.. couldnt be better. <grin>

>
>
> Best to you all,
>
> Brian Trout
> Quarryville, PA
> btrout@desupernet.net
>

Richard Brekne
I.C.P.T.G.  N.P.T.F.
Bergen, Norway