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Duplex Scale

Posted By: Faiz

Duplex Scale - 05/26/18 12:32 PM

Hi, good afternoon (from here hehe)

I just realized that some pianos have their tenor section rear duplex muted with felt, but on some pianos don't, and some has duplex metal bar, but muted as well.
Interesting...

Some picts :
[Linked Image]
Above is a pict of Yamaha G2, it has the tenor duplex open

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[Linked Image]
On Yamaha C7
But I saw some Yamaha C7 with open tenor duplex as well (I don't have the picture of it)

[Linked Image]
[Linked Image]
[Linked Image]
On Yamaha CF

I am curious what is the purpose of this? What's the difference?
Thanks


(Sorry low quality pictures, it was taken with my phone)
Posted By: PianoWorksATL

Re: Duplex Scale - 05/26/18 03:00 PM

Rear duplex scaling is often muted for close to medium distance microphone placement. The frequencies in the tenor can be problematic (recording or not), and muting is an easy solution.
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/26/18 03:15 PM

Many of those lowest duplexed hitching lengths are somewhere near the pitch of the top two and a half octaves. They are never and can never be set to pitches that don't create some problems with hearing the upper note clearly to make tuning the piano easier. So some tuners mute them out if they hear a problem when tuning. Even at the factory, thus you see some variation imparted by the final tone regulators.

If you wish to learn more about duplex scales, I have a US Patent called Fully Tempered Duplex Scale that solves the troubles with duplex scales. There is a PW thread of the same name you can see. Duplex scale problems also include issues arising from Longitudinal modes.
Posted By: BDB

Re: Duplex Scale - 05/26/18 04:52 PM

This just demonstrates the lack of efficacy of duplex scaling.
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/26/18 05:39 PM

BDB, There is no lack of efficacy to the Fully Tempered Duplex Scale. Duplexing maximizes the benefits of pivot termination. Fully Tempering it eliminates the transverse and longitudinal mode noises.
Posted By: BDB

Re: Duplex Scale - 05/26/18 06:23 PM

I eliminate the transverse, longitudinal, and all other mode noises by not playing the piano. This is something that anyone can easily replicate for themselves, without paying anyone a royalty.

If I do play the piano, I like it to make some noise.
Posted By: Faiz

Re: Duplex Scale - 05/26/18 08:54 PM

Thanks for the answer guys!

another curiosity, this C7 came from the factory has muted on this section, but they put the metal bar anyway, does that mean we can customize whether we want it open or muted?
[Linked Image]
Posted By: BDB

Re: Duplex Scale - 05/26/18 09:05 PM

If it is your piano, you can do whatever you want. The metal bar is there to establish the height of the strings above the plate. There is clearly no relationship between the length from the bridge to the tips of the plate to either the length or the pitch of the string.
Posted By: Faiz

Re: Duplex Scale - 05/26/18 09:15 PM

ahhh I see
Thanks
Posted By: Retsacnal

Re: Duplex Scale - 05/26/18 10:56 PM

Faiz, in what part of Indonesia do you live?
My wife grew up in Jakarta.
Posted By: P W Grey

Re: Duplex Scale - 05/27/18 12:09 AM

Yes, you can mute part or all of it at your discretion.

To test out if you really want to or not, simply use scotch tape or masking tape (TEMPORARILY) TO mute all of it (front and rear), then play the piano and see if you like it better. Then progressively remove the tape and play until you get the sound you really like. Then use thin felt or cloth similar to what the factory used to mute the sections you want.

I do this regularly for people who don't like all the high frequency "noise" they are hearing. DO NOT leave tape on the strings for long as it can leave residue. Repeat: Do not leave the tape on the strings! It is simply a diagnostic procedure...not a cure.

Pwg
Posted By: Faiz

Re: Duplex Scale - 05/27/18 05:58 AM

Cheers! From Yogyakarta
Posted By: Faiz

Re: Duplex Scale - 05/27/18 06:04 AM

Thanks for the tip... thumb
Posted By: Roy123

Re: Duplex Scale - 05/28/18 01:29 PM

Wouldn't it be fair to say that the main purpose of the metal bars in question is to set the rear down-bearing? Without them, a vertical hitch pin, as is used in some Baldwins, would be required. I also seem to recall Del saying that rear duplexes are essentially worthless. Is my memory correct? Of course, you need some back-scale length to allow the bridge to move, especially in the bass, but, that consideration is unrelated to the idea that a rear duplex could be tuned to some good effect.
Posted By: P W Grey

Re: Duplex Scale - 05/28/18 02:41 PM

In essence I think the duplex system was simply an effort to utilize the otherwise necessary "waste" length of string in such a way as to benefit the sound of the piano. The design on paper certainly makes sense, but in actual manufacturing practice it does not ALWAYS seem to do so. But, it is a seriously good advertising thing at least.

Ed McMorrow has certainly proven that it CAN work, given enough attention.

Unfortunately, it can also contribute to some very difficult tonal issues. And once it is set up and installed at the factory it is very hard to change it (Steinway style anyway). At least we do have the option of muting some or all of it, OR using PitchLock string couplers to modify it in various ways.

Pwg
Posted By: BDB

Re: Duplex Scale - 05/28/18 03:13 PM

There are all sorts of things which are attributed to duplex scales that can be attributed to other things. Claims that they make a difference would not survive a true blind test.
Posted By: Roy123

Re: Duplex Scale - 05/28/18 05:06 PM

Originally Posted by BDB
There are all sorts of things which are attributed to duplex scales that can be attributed to other things. Claims that they make a difference would not survive a true blind test.


It is also my sense that most of the time, what you say is true.
Posted By: Rickster

Re: Duplex Scale - 05/28/18 05:50 PM

I don't have anything of substance to add to this discussion, other than to say that I've already been down this duplex scale road and done a lot of research on the subject. What I learned was that not all piano manufacturers, even some of the more reputable higher-end, tier-1 makers, use a duplex scale on their grand pianos. I also read that Steinway was among the first makers to use the duplex scale, and many other companies followed their lead, in hopes of copying some of their success, I suppose.

Rick
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/29/18 03:30 AM

The part Steinway got correct in their Duplex Scale Patent of 1872 was the significance of a "pivot" termination. Pivot significance arises because the high stiffness of piano wire allows mode information to move beyond the terminations provided for the normal hammer strike induced transverse modes. This is at the front duplex located between the capo bar and the tuning pin. The rear duplexes, (which is what most people are talking about when they use the term duplex), have far less significance.

What Steinway got incorrect was claiming that the front duplex should be in a whole number relationship with the transverse modes of the speaking length. They also claimed to "harmonize" the longitudinal modes with the transverse. This is not possible.

What I discovered was that some duplex scale noises arise from beats between inaudible, high frequency Longitudinal modes.

Then I devised a way to build a duplex system that apportions the pivot termination effect smoothly across the compass and damps unwanted Longitudinal mode interactions.
Posted By: KLX-F1

Re: Duplex Scale - 05/29/18 04:25 AM

..and this was the one part of Steinway design that arose directly from correspondence between C.F. Theodore Steinway and Dr. Hermann von Helmholtz, if I remember correctly. Helmholtz wrote a letter afterwards exclaiming the beauty of tone they had finally produced..

I'd like to learn more about your patent, Ed. Very interesting..
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/29/18 02:56 PM

KLX-F1,
Thanks for your interest. My US Patent is #9,117,421. There is a thread on PW that include "Fully Tempered Duplex Scale in the title. There is also one on PTG.org Pianotech Forum.

I will be giving a class on FTDS at the PTG Convention in Lancaster Pennsylvania this July. I am bringing a 1979 Chickering 501 that includes it. Hope to see you all there!
Posted By: BDB

Re: Duplex Scale - 05/29/18 03:14 PM

Just keep in mind that a patent is granted on only one basis: that there is no previous patent that covers the same thing. All the patent does is give the grantee the right to defend infringements in court, at which point the patent may be upheld or nullified in the process of disputing the infringement. The patent is not a guarantee that the patented device does anything that it is claimed to do.
Posted By: P W Grey

Re: Duplex Scale - 05/29/18 04:32 PM

BDB,

Though what you say is true, it does not seem necessary to cast doubt as you have UNLESS of course you have personal experience to the contrary, so as to be able to speak thus.

Though I have not as yet seen it in action, I have heard from others who have applied it that it does in fact fix the defects built into the Steinway aliquot arrangement. I am interested to see it perform before I make a judgement.

Planning to be there in Lancaster.

Pwg
Posted By: Faiz

Re: Duplex Scale - 05/29/18 04:55 PM

Interesting!
Do you have demonstration video or audio sample of piano with FTDS?
Posted By: BDB

Re: Duplex Scale - 05/29/18 05:02 PM

I do not know what the supposed defects in the Steinway aliquot arrangement are, so if I heard one of the pianos, I would not be able to tell whether it fixes them or not.

I do know that some of the claims made about it make absolutely no sense mathematically or physically. I also know that the biggest defect that things like this are designed to fix are often the hollow sound in one's wallet. So it is always well to be reminded that "It Ain't Necessarily So!"
Posted By: P W Grey

Re: Duplex Scale - 05/29/18 09:34 PM

Of course, some of the problems come from restringing. The standard wire used today is significantly stronger and harder than the wire that many if these instruments were originally strung with. That in itself seems to aggravate the front aliquots (in my experience). So of course if the original design was done in reference to the type of wire used then (obviously so), then we would expect some difficulties now. Same as if we strung an American made piano with Asian wire. It's not going to be the same and there might be unintended consequences.

I think Ed' s research is valuable. It is not uncommon for a design "on paper" to be a bit different in practical application. And sometimes it need a to be "re-thought". Of course, whether the re-application is worth the expense of doing so is a question that cannot be truly answered by us here and now. But if it consistently can be proven to have turned a mediocre piano into a fantastic one...well, that is certainly worth digging into IMO.

Pwg
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/30/18 04:56 AM

If BDB has never heard any "noises' in a piano with a standard duplex scale, he either has an incidence of good fortune equal to the odds of being struck by a meteorite thrown by an extraterrestrial, or he is deaf to the problem.
Posted By: Norbert

Re: Duplex Scale - 05/30/18 05:45 AM

Quote
If BDB has never heard any "noises' in a piano with a standard duplex scale, he either has an incidence of good fortune equal to the odds of being struck by a meteorite thrown by an extraterrestrial, or he is deaf to the problem.


I agree.

Except believe that "a meteorite thrown by an extraterrestrial" is the most likely of explanations here!

Norbert grin
Posted By: BDB

Re: Duplex Scale - 05/30/18 06:09 AM

I have heard noises in pianos with duplex scales. I cannot attribute them to the duplex scale, though, unless it is something that I have been able to alleviate without redesigning the piano.

I think there was someone here with the tag line: If the only tool you have is a hammer, everything looks like a nail. I have acquired a few more tools in my kit.
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/30/18 02:05 PM

BDB, Making in-situ test modifications to an existing standard duplex is how I first tested the precepts used to derive FTDS. If using those design tools is not good enough for you, what do you use?
Posted By: BDB

Re: Duplex Scale - 05/30/18 03:35 PM

I use whatever works. It is difficult to say precisely what the method is when it depends on what the problem is.

One thing I do know is that if there is a problem that shows up on one sample of a model of piano and does not appear on another, it is not a design issue. That is a logical conclusion. Logic is one of my tools.
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/30/18 09:47 PM

But tolerances vary from piano to piano and are changed over time and drift with time so an intended design at one point is often no longer extant. I employ logic as well, but logic must not be misused to simplify away factors that exist. The foremost tool in logic is Occam's razor.
Posted By: BDB

Re: Duplex Scale - 05/30/18 10:42 PM

Occam's Razor says that if someone can do something simply, that someone who needs to do it in a far more complicated way is wrong.
Posted By: Retsacnal

Re: Duplex Scale - 05/30/18 11:16 PM

Originally Posted by Faiz
Cheers! From Yogyakarta

I have never been to Yogyakarta. Maybe one day....
Posted By: Ed McMorrow, RPT

Re: Duplex Scale - 05/31/18 04:00 AM

BDB, Occam's razor says that you test the simplest explanation first. There is much art in deriving the simplest explanation. That art can involve much study of seemingly minor details. With musical instruments, the context of use is often the most difficult part to understand all of the possibilities.
Posted By: P W Grey

Re: Duplex Scale - 06/01/18 03:01 PM

Another issue with aliquot scales is that they can have false beats as bad or worse than SL strings. Just the nature of the beast.

Pwg
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