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
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