Duplicity on a Grand Scale

[Michael Jorgensen]

Ron,
    That is pretty interesting. I wonder if various confugurations of
duplex (i.e angle and length) result also in a change in timber of the
tone which bleeds across.  Perhaps an adjustable couterbearing bar could
be built for a few notes on a real piano.  Then test with the RCT
pianalyzer how various configurations of duplex affect relative overtone
intensity.  Perhaps one could control/voice or bleed out from the
speaking length the undesireable overtones into the duplex, i.e a useful
duplex.
Just a thought.
-Mike

  

  Ron Nossaman wrote:
> 
> Hi gang,
> 
> It's me again, and I've got something for you. Out tuning today, I got to
> dinking with the duplexes, and I observed an interesting thing or two. You
> can too, if you bother to try.
> 
> The first thing I did was chose a noisy string and touched the front duplex
> while playing the note. The tone got considerably clearer. I then plucked
> the speaking length while holding the key down to keep the damper up, and
> not touching the front duplex and the noise was back. No surprises here.
> Then, still holding the key down, I plucked the duplex and the speaking
> length sounded at the fundamental. Cool! Proof positive that string energy
> bleeds past the v-bar to the next segment. This was a low bearing angle,
> long front duplex, so that wasn't any surprise either. I located the longest
> duplex and plucked that. The speaking length fundamental sounded, but there
> was a lot of added garbage coming from the front duplex segment that
> rendered the combination of the two less than pleasant. What do you suppose
> happens at the agraffes? I then went down to the tenor section and plucked
> the, roughly, 10 mm long segment between the understring felt and the
> agraffe. The speaking length sounded the fundamental. Really cool. The
> bearing angle here was much steeper than in the treble ( about 20 degrees),
> and the segment was super short and muted by cloth, and the brass of the
> agraffe was much softer than the v-bar, but it still worked. What the heck,
> I thought, let's try the bass. Yep, same thing, in spite of the even steeper
> bearing angle through the agraffe.
> 
> Later, I tuned a new console. No intentional front duplex to dink with, but
> there was that nice short, high bearing angle segment between the v-bar and
> the pressure bar. Key down, I reached in with my junk pocket knife blade (as
> opposed to my surgery blade, but that's on the other knife anyway), and
> plucked the segment. The speaking length sounded at the fundamental. Well,
> in the interest of symmetry, I've got to try the bass too. Key down, I
> plucked the segment between the upper bearing pin and the tuning pin and the
> speaking length didn't sound like anything I could identify because the
> segment I plucked drowned it out and turned the combined sounds into
> garbage. Playing the note normally, I couldn't specifically pick out the
> sound of the "duplex" (what's that little sucker called anyway?), but I
> begin to wonder how much, if any, of the bass garbage we can't seem to tune
> out comes from this.
> 
> Anyway, the on the spot conclusions were that increased bearing angle
> doesn't entirely stop the energy leakage past the agraffe or v-bar. With the
> sampling I had, I can't separate the effects of angle and duplex length, but
> it is quite obvious that the shorter duplexes are quieter at a low bearing
> angle, and it's reasonable to expect that a higher angle will result in
> better termination.
> 
> Entertainment is where you find it when tuning.
> 
>  Ron