Tuning Duplex

[Ron Nossaman]

>Greetings listees,
>    I wonder if someone could help me understand something. When tuning
>the rear duplex doesn't that affect the rear bearing? If so could that
>not be what accounts for the increased sustain and or projection and not
>the fact that the duplex is in fact temporarily in tune with the
>speaking length? This would seem to make more sense to me. Also if the
>rear duplexes are "in tune" and are all sounding simultaneously with the
>bridge movement, what good does it do? In order to be effective wouldn't
>the duplex segment need a damper too?
>Thanks in advance for the enlightenment.
>--
>Greg Newell


Hi Greg,
Tuning the rear duplex is an attempt to make a design feature work like it
was intended to by moving the aliquots to where they presumably should have
been all along. Also presumably, the positioning isn't that far off or it
was never intended to be a tuned system in the first place. With that in
mind, moving an aliquot a millimeter or two won't have a realistically
measurable affect on downbearing angles across the bridge. There's not a
lot of difference between a 1:1000 slope, and a 1:1005 slope. It will
immediately affect the back scale segment tensions because the deflection
angle from the aliquot to the hitch will change a whole lot more than the
downbearing angle at the bridge because it was a much higher angle in the
first place, and the aliquot movement was a much higher proportion of the
string lengths involved.

Does the bearing change account for increased sustain and power? I
seriously doubt it. Does tuning the duplex by merely moving the aliquot
increase sustain and power?

Nobody wants to damp a tuned duplex because they are supposed to make
noise. The question is what sort of noise they make. Once again: there is
no detectable direct string energy transfer across the bridge. The speaking
segments move the bridge, the bridge moves the rear duplex. For the rear
duplex to sound, the bridge must move. When the entire bridge moves, all of
the duplexes coupled to the bridge move with it. It's not just that duplex
segments directly across the bridge from the played note that are sounding.
They all are, so putting dampers on the duplex would be functionally no
different than braiding it off, only considerably more expensive. 

Ron N