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Tuning duplex scales?
#2850832 05/21/19 05:08 PM
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Hi Everyone,

I have a '67 Baldwin R that I love and I (foolishly?) thought it would be interesting to try tuning it. My thought process was along the lines of "old guy buys old car and learns to fix it for 'fun'."
After a few months, some expensive software and a very annoyed wife, it finally sounds solidly "ok" again. crazy
The most fascinating part of this whole process is learning just how much I didn't know when getting started and I suppose I'm just scratching the surface of what I still don't know.
The forums have been very helpful and so have videos from forum members.

Anyway, I've been looking over the forums trying to find a good answer about whether or not front and rear duplex scales can/should be tuned.
Duplex tuning wasn't even something I was aware of until yesterday when I was reading threads about a bass unison that wouldn't tune.

I went to the piano this morning and plucked the strings with a pick and they are 1) pretty badly out of tune with each other and 2) definitely not tuned to P2 or P3 as described in the forums.
For example C5's rear was somewhere around a G#6 which doesn't seem correct.

So here are the questions:
1) Does it really matter?
Seems like there are mixed opinions on this. Some suggest just muting them if they sound bad, others (like Ed McMorrow with the FTDS work) say they should be tuned.
Part of the reason I care is that there's a lot of 'sizzle' around the 5th octave (vbar/capo area) that is kind of unpleasant and I thought it might be related to NSL noise.
2) Is it reasonable or possible to tune these?
The Baldwin R doesn't have an "adjustable" duplex and strings are shared.
3) How?
I'm assuming that it would involve trying to get both sides of the string under equal tension and then somehow trying to balance the tension between the speaking length and NSL.
4) Should I just give up and find someone reasonably obsessed (hehe) to come do it for me?

Apologies for the naive post - I'm still learning the depths of my ignorance here. smile

Last edited by KylePNW; 05/21/19 05:15 PM.
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Re: Tuning duplex scales?
KylePNW #2850848 05/21/19 06:12 PM
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Actually, Baldwin is a good make to look at for discussing the value of duplex scales.

Early Baldwins had aliquots that were truly non-tunable: There was a pin in the bottom of them that went into holes in the plate.
Later Baldwins did not have the pin or the holes.
Still later Baldwins, with Acu-Just hitch pins, did not have aliquots at all, so there was no duplex scale, at least behind the bridge.

So that may give you an idea of how important Baldwin believed duplex scaling to be.


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Re: Tuning duplex scales?
KylePNW #2850881 05/21/19 08:33 PM
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KylePNW, you may find this interesting reading: http://homes.ioc.ee/stulov/slovak06.pdf

This study was by Estonia, who incorporates tunable front and rear duplexes in their grands, as does Fazioli and Ravenscroft, Mason.& Hamlin, and others.

I won't guess as to the motives of Baldwin when they went to the accujust hitch pins. In that case, I think the merits of having independently adjustable down bearing for each string outweighed the virtues of duplex tuning.

Ed Mcmorrow can chime in if he wishes to tell you what exactly tuning a front duplex means to him.


fine grand piano custom rebuilding, piano technician and tuner
Re: Tuning duplex scales?
KylePNW #2850902 05/21/19 10:04 PM
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You may want to try an experiment in muting off all the duplex areas and analyzing the result. A reasonable number of people prefer the sound of their piano without the aliquots ringing.

To test the effect put tape on all aliquot sections, front, rear, where ever. Then play and see what you think. Then, selectively remove tape one section at a time. If you like a certain combination make note of it. Remove the tape and thread thin felt through all that you want, leaving the sections (if any) ringing that you want.

Some ideas are great on paper but in reality don't work quite the way we intended. You can "tune" them this way (tune them out maybe).

However I concur that Ed M. Can doubtlessly give numerous reasons why and how to actually TUNE them.

Pwg


Peter W. Grey, RPT
New Hampshire Seacoast
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Re: Tuning duplex scales?
KylePNW #2850914 05/21/19 11:15 PM
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Thanks for asking me to comment.

Front duplex segments, (the ones between capo and tuning pin), must be de-tuned from whole number relationship with the struck segment.

Rear duplexes function best when they are close to the fundamental of the struck segment and damped.

The "sizzle" noise you are hearing may well be a too round V-bar finally allowing the old strings to buzz because they bent over time enough to where the speaking length is actually able to vibrate into the front edge of the V-bar.

It could also be that the front duplex is too close to a whole number relationship with the speaking length. (Measure the speaking length of both the struck segment and the duplex segment and divide the duplex length into the struck segment length and if the result is close to a whole number, that is a likely noise source).

It could also be inaudible longitudinal modes beating with themselves in the audible frequency range.


In a seemingly infinite universe-infinite human creativity is-seemingly possible.
According to NASA, 93% of the earth like planets possible in the known universe have yet to be formed.
Contact: Ed@LightHammerpiano.com
Re: Tuning duplex scales?
KylePNW #2850923 05/21/19 11:57 PM
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I would estimate that the possibility that the sizzle in your piano is due to voicing and wear in the hammers is very close to 100%. Try filing the hammers. You should not need to take off all the string groove to make a noticeable difference.


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Re: Tuning duplex scales?
KylePNW #2850982 05/22/19 05:33 AM
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BDB's contention that this noise almost always originates in the hammers can be readily tested when one hears it coming from notes that have front duplexes. Sound an offending note, and put your finger on the strings in the front duplex area. If it goes away with the touch, it is not originating in the hammers, but at the Capo V bar, being either too rounded in origin, or rounded over by string cuts created by years of heavy playing. It is as Ed describes,and there is no controversy as to this problem, except perhaps in BDB's mind.

The cure for the string grooves is to relieve the string cuts and reshape the V bar into a narrower profile. Rebuilders do this all the time.

It can also be said that piano makers are not always attentive to creating a proper profile, so sometimes you can hear this sizzle right out of the gate on new pianos.


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Re: Tuning duplex scales?
BDB #2851063 05/22/19 10:24 AM
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So BDB, have you ever experienced a V-bar shape that you thought was too blunt?

Have you ever reshaped a V-bar to a V-shape and compared the tone difference?


In a seemingly infinite universe-infinite human creativity is-seemingly possible.
According to NASA, 93% of the earth like planets possible in the known universe have yet to be formed.
Contact: Ed@LightHammerpiano.com
Re: Tuning duplex scales?
KylePNW #2851077 05/22/19 11:01 AM
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I can attest to the importance of V bar shape! And it goes back a long way.

Ed is CORRECT! Listen to him.

Pwg


Peter W. Grey, RPT
New Hampshire Seacoast
www.seacoastpianodoctor.com
pianodoctor57@gmail.com
https://www.youtube.com/watch?v=PK0T7_I_nV8
Re: Tuning duplex scales?
KylePNW #2851080 05/22/19 11:09 AM
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By all means you can try the $1000 cure before you try the $100 cure. But I recommend doing those in the opposite order.


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Re: Tuning duplex scales?
KylePNW #2851104 05/22/19 11:50 AM
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Absolutely BDB...start simple (that's a no brainer), but the cure depends on a proper diagnosis. First check for the easy, but be ready to commit to the complicated if necessary. A V bar buzz can EASILY parade as a soundboard or bridge problem.

I recently restored an A, an O, and in the process of a B...ALL of which had seriously poorly shaped Vbars in various places straight from the factory (or possibly from poor treatment in previous "rebuilds"). I do not enjoy tackling this in a strung piano. PITN! Literally.

Hopefully though your buzzes are elsewhere. That would be nice.

Pwg


Peter W. Grey, RPT
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https://www.youtube.com/watch?v=PK0T7_I_nV8
Re: Tuning duplex scales?
KylePNW #2851121 05/22/19 12:36 PM
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BDB, do you charge a $1000 to diagnose a buzzing front duplex by putting your finger on the offender?

I believe you have done some rebuilding. Don't you listen to the front duplexes before teardown, examine the V bar after destringing. and reprofile as needed? Every rebuilder I know does just that.


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Re: Tuning duplex scales?
KylePNW #2851132 05/22/19 12:50 PM
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More and more as I became more adept at basic service, I found that pianos need less rebuilding than people claim.


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Re: Tuning duplex scales?
KylePNW #2851136 05/22/19 12:57 PM
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Right on the mark, Peter. His buzzes are elsewhere.....


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Re: Tuning duplex scales?
KylePNW #2851203 05/22/19 03:39 PM
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Thank you for all of the feedback.

A few updates:
1) I think maybe the duplex _is_ tunable? I don't know if the little metal bridges are movable or glued/fixed to the harp. Here's a picture.
[Linked Image]
2) In any case, I'm not going to bother messing around with them. From reading more, it sounds like as long as they are close, they achieve the goal (adding some overtone ring, bridge impedance magic???)
3) I didn't measure the front duplex length to the speaking length ratio, but the front sounds much more "in tune" with the primary note... it sounds like 2 to 4 octaves higher. That would lead me to think that they are some integral multiple of the speaking length.

As for the sizzle, a few more notes on that.
1) many of the strings there are hard to tune. They seem... unstable (???) throughout the attack/sustain. I don't know if those are false beats or something else, but the pitch (of a single string) will start sharp, fall flat go back sharp, and land in tune then fall flat again. Whatever the cause, the tone is not clean and pure. I'm not even sure how to begin tuning the unisons because each string is so wild.
2) I gently put my finger one of the worst offenders in front of the capo and struck the note. The note sounded very dead and I felt a lot of vibration in the string. I'm going to guess this is because some of the vibration is 'leaking' into the front duplex because the termination isn't clean. The last time I had a tech come out, he tried pulling the string into the capo to seat it better, but I'm guessing that didn't really work to solve the issue.

In any case, it sounds like the capo is part of the sizzle problem.
I ordered some pitch locks (for a few really ugly bass bichords), but some posts have suggested they may help in the capo section too?

As fun aside, when messing around with it this morning I learned what happens if your phone falls behind the fallboard. eek

Re: Tuning duplex scales?
KylePNW #2851256 05/22/19 07:54 PM
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Lol...good one Will. I missed that.


PitchLocks work very well in the capo area. You need the small ones for that. Large for the bass. Just be careful that you don't drop too many down into the action...😢

You can look at the V bar with a mirror and flashlight with the action out. Are the annoying sounds limited to the V bar area? Or do they also extend into the agraffe section? A better test might have been to literally move the entire unison over slightly to get it out of whatever grooves might be there already. Then listen to it. If it clears up, you know what your problem is. If it doesnt, look elsewhere.

As to the tuning issue, some pianos are simply like that (actually virtually all do it to some degree). Assuming you are using an ETD you "see" more of it than we aural tuners do. We just go with the flow and tune it with our ears.

Pwg

Last edited by P W Grey; 05/22/19 07:56 PM.

Peter W. Grey, RPT
New Hampshire Seacoast
www.seacoastpianodoctor.com
pianodoctor57@gmail.com
https://www.youtube.com/watch?v=PK0T7_I_nV8
Re: Tuning duplex scales?
P W Grey #2851278 05/22/19 10:10 PM
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It's mainly the capo section. The C5/C#5 are the last agraffe strings and C5 can be a little harsh. Mainly it's (C5 to C6). Above that it doesn't seem as bad - but I really don't play up there as much so maybe I just don't notice it as much?

If I wanted to move the unison over a bit, how would I do that? Can I do it under tension and just push down and over or should I loosen those strings and then slide them over?

I am using an ETD (Verituner) and it's very jumpy on those notes, but even when tuning the unison (which I try to finish up by ear), I don't really know would be the best to tune to. So far, I've been listening for beats in P2 and P3 but the pitches are so unstable, I'm not even sure what part of the attack/sustain I should even try for. In the high treble, I have tuned the very initial attack and that sounds pretty good. If I tried that in this octave, I can get the attack to sound good and then have a busy sustain or have a busy attack that settles after a second. I guess if I have to pick one, the sustain might be more important so chords sound clean.

In theory it all seemed pretty straightforward... (famous last words) smile

Re: Tuning duplex scales?
KylePNW #2851395 05/23/19 08:56 AM
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I was not really thinking of suggesting that you do it. Your tech has the tools, etc.

Have you tried muting off the entire aliquot sections yet?

Pwg


Peter W. Grey, RPT
New Hampshire Seacoast
www.seacoastpianodoctor.com
pianodoctor57@gmail.com
https://www.youtube.com/watch?v=PK0T7_I_nV8
Re: Tuning duplex scales?
Ed McMorrow, RPT #2851693 05/24/19 08:37 AM
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Originally Posted by Ed McMorrow, RPT
Rear duplexes function best when they are close to the fundamental of the struck segment and damped.


Ed,
Except in the highest notes, how can the rear duplex approach the fundamental of the speaking length?
And how do you damp the rear duplex. I don't think I have spotted any changes from design in your pictures.


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Re: Tuning duplex scales?
Craig Hair #2851744 05/24/19 10:27 AM
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Hi Craig,
I have one piano with the top octave having hitching length equal to speaking length. Of course it would be unrealistic to have this continued much lower than the top two octaves of the standard piano compass.

Damping of ancillary string segments is achieved in the usual ways. Soft cloth of some sort.


In a seemingly infinite universe-infinite human creativity is-seemingly possible.
According to NASA, 93% of the earth like planets possible in the known universe have yet to be formed.
Contact: Ed@LightHammerpiano.com

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