On 8/19/2014 10:33 PM, Edward McMorrow via Piano Technicians Guild wrote:
> Well Ron, I cited proof, as you requested, for the behavior of
> L-modes crossing pivot terminations.
No, you didn't. You cited your interpretation as proof. Proof is some
documentation or demonstration of measurement of longitudinal mode
outside the speaking length. No such measurement or documentation seems
to exist.
>I didn't accuse you of bickering.
I didn't say you had.
>I don't mind questions about my evidence.
You just can't produce that evidence.
> But questions
> whether my Fully Tempered Duplex Scale sounds different than the
> prior art in a forum of peers such as this one when independent
> technicians have reported that it does-are tiresome to me.
Has anyone at all other than you said anything at all about the sound of
your system? If they have, I didn't see it go by, yet that's been your
standard pitch in avoidance of answering specific questions. You, on the
other hand have nothing good to say about short front duplexes with
brass counter bearings that make no claim to otherworldly physics but
are clean, quiet, and do exactly what the practitioners of that system
are after.
> You and I agree that duplex scales have problems. I have a novel
> solution. I would welcome you to experience it!
It doesn't take our agreement to know that the entire technical
community has fought tuned front duplexes for a very long time. This
isn't debatable, nor worthy of the repeated mention it's gotten. I'd
settle for some real data (documentation of measurement) to back up the
claim of longitudinal vibrations crossing bearing points. So far, there
has been absolutely none. This has been the fundamental question from
the beginning, simple and straightforward, and we are no closer to an
answer now than we were hundreds of messages ago when I first asked it.
Ron N
Original Message------
I am starting a new thread, as the one labeled reshaping the capo bar in situ has long since wandered to other aspects of the front duplex. I'd tag along on Jim Ialeggio's thread, but its topic is too narrow. I am doing this partly to give Ed McMorrow an opportunity to explain his ideas, but would like to try to keep discussion within the front duplex and its physical layout, at least to start with.
I am going to try to set the stage by describing a typical successful front duplex (some may argue about "success" but that can be part of the discussion): that of Steinway and its imitators. In that design, we have termination bars cast into the plate near the tuning pins, defining a section of the non-speaking length of the strings that is free to vibrate. There are typically three bars in each capo section, and they are angled so that the length of free string is in the 30 - 50 mm range, usually 30 - 40, 35 - 45, and with one or two toward the agraffe section that get to 50 mm or a bit above. The bars are angled so that the largest segments are to the bass, smallest to the treble.
The angle from speaking to duplex length tends to be about 25º in Steinway. For comparison, Yamaha tends to be around 20º, and Mason & Hamlin BB goes from 25º in the highest section to 35º in its lowest section (M & H has three capo sections, going lower than anyone else).
This gives us a basis for comparison. Now I am going to describe what I think Ed McMorrow is recommending in his "Fully Tempered Duplex Scale" model. He focuses on the concept of pivoting termination, where the termination of the string is a pivot, and a string will be more free to pivot around that termination if the non-speaking portion is longer. (By contrast, the termination at the bridge is more or less "clamped," and the string pivots very little there. The agraffe section is considerably more "clamped" as there is a very short segment before the string is bearing on felt in most cases.) Ed believes that the duplex lengths should get larger toward the high treble, to give the highest strings more freedom to vibrate, and to create a taper from the agraffe section to the duplex section. He tends to have 50+ mm duplex segments at the very top (where Steinway et al will have 30 mm or so).
Ed says that he has no specification for angle between speaking length and duplex, and that the longer duplex sections in the highest treble are not a problem for him. Perhaps this has to do with his use of a high density plastic for the termination bars. A question might be raised as to whether smaller angles provide freer pivoting, and as to what parameters there are. The most commonly held view holds that if the angle gets below 20º or so, the duplex segment needs to be quite short, perhaps under 20 mm, and that an angle of at least 25º is needed for segments longer than 30 mm or so (the exact numbers are subject to debate).
So, leaving all talk of L-modes and T-modes aside, this is the basic initial design. I welcome Ed's comments and those of others.
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Fred Sturm
University of New Mexico
http://fredsturm.net
"When I smell a flower, I don't think about how it was cultivated. I like to listen to music the same way." -Federico Mompou
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