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#1986006 - 11/13/12 05:08 AM Why do left of tri-chords develop false beats more often?
Chris Leslie Offline
500 Post Club Member

Registered: 01/01/11
Posts: 720
Loc: Canberra, ACT, Australia
This occurrence has been mentioned before by some but without any plausible theories. One difference is the length of the non-speaking section, but I don't see how this could do it.

Also, has anybody noticed that often it is possible to almost disguise some false beating strings by tuning a unison string in a particular way? Is it by creating a beating unison that maybe cancels the real false beat, or is it my imagination?

Regards
Chris
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http://www.chrisleslie.com.au

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#1986022 - 11/13/12 06:22 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Olek Offline
7000 Post Club Member

Registered: 03/14/08
Posts: 7904
Loc: France
The left side of the hammers is thinner than the right side, and the impact is stronger on the right side. (anyway when the hammers are located for a faster UC pedal, as it is the case often.

A less frank impact is more prone to create "simili" false beats, in my opinion. I did not notice that this could be something with the string.

If the false beat is real, it can be heard by plucking the wire.
The 1/3 -2/3 hammer location is creating some slight unbalance, I would investigate that first(I am not saying you are confusing things, just that I did not notice the effect you are talking about)

False beats can be hidden somehow, by changing the dwell timing while tuning, as you say creating a simile beat by working the stabilization time at the 2nd partial level so it match the false beat.

Due to incoherency in the partials spectra, (reasons may be the slight length difference noticed between left /right string, or other causes) there is always some room, when tuning an unison, if we focus on the fundamental energy that energy tend to straighten the higher partials, the whole tone moan slightly but this is not always very apparent (more at FFF). IF we focus on second partial or above then the fundamental is auto tuned, with more largeness)

But the moment where the partials are coupling may be soon enough before, the long term stabilization that happens (probably) via the bridge, and that is ruling the unison in his longer part.

That is how I perceive those things, whithout precise measure or analysis, but for sure the perfect coupling (reinforcing) of the partials is enlighting the fundamental if done soon enough in the tone. (I like to open the octave to help my ear and also to perceive the sympathetic resonance better) (sympathetic ??? wink





Edited by Kamin (11/13/12 06:24 AM)
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#1986025 - 11/13/12 06:41 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
rxd Offline
1000 Post Club Member

Registered: 03/11/09
Posts: 1771
Loc: London, England
Ok, how's this?... The speakinlg length bridge pin is nearer to the edge of the bridge giving a less secure termination. There are old old well built pianos that have bridge pins that more closely follow the line of the bridge. I don't find the falseness pattern in these pianos.

I often tune it last of the three and put it where it sounds least worst. Just drop it in quickly almost by instinct as though it weren't false and you'll find it's the best place for it. Trouble is, there's the temptation to make it that little bit better. Resist the temptation.

In severe cases, I get the best results quickly by tuning each string electronically to the same frequency.


Edited by rxd (11/13/12 07:23 AM)
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"in theory, practice and theory are the same thing. In practice, they're not." - Lawrence P. 'Yogi' Berra.

Eschew obfuscation.



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#1986039 - 11/13/12 08:03 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Olek Offline
7000 Post Club Member

Registered: 03/14/08
Posts: 7904
Loc: France
I will have to check that more precisely, I can imagine what you are telling about, but does not put it in the "false beat" category. would be a "less strong, or less thick" tone..

As I listen to the unison as a whole it probably does not bother me much.
Anyway differences between strings is just the norm, only on rare pianos there is a good similitude between the 3 strings.

Energy wise they can be managed, that is what counts for me.


Edited by Kamin (11/13/12 08:04 AM)
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#1986112 - 11/13/12 11:25 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Supply Offline
3000 Post Club Member

Registered: 09/11/06
Posts: 3919
Loc: Vancouver Island, BC, Canada
I have not found that the left string is more often false than the one on the right.
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Jurgen Goering
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#1986120 - 11/13/12 11:37 AM Re: Why do left of tri-chords develop false beats more often? [Re: Supply]
UnrightTooner Offline
4000 Post Club Member

Registered: 11/13/08
Posts: 4954
Loc: Bradford County, PA
Originally Posted By: Supply
I have not found that the left string is more often false than the one on the right.


I have, FWIW. I often tune right-center-left in the treble when there are problems.
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Part-Time Tuner
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#1986124 - 11/13/12 11:47 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
TunerJeff Offline
Full Member

Registered: 06/22/11
Posts: 494
Loc: Oregon Coast
I'm with Jurgen on that one. I have not noted that the left-string is more prone to false beats. Of course...I've only been at it for 30 years or so, I'll keep my ears open!

If the false beat is audible when plucked, there's not much to do. Seating at the bridges, straightening the bends off the bridge, aligning at the capo or agraffe. Using a brass-drift to shift the wire at the capo, or just firmly pressing to insure good contact. The whole host of things we do to make sure the problem is somewhere other than the wire! Just checking all the bearings can help. But....not always. (sigh)

An 'out there' possibility for false beats, when nothing else works, was suggested to me by a builder-top-tech (service manager). On a note in the C5-C6 range which had a false beat; reduce the tension on both sides of the hitch-pin (both strings) and purposely crank one of the strings to fairly high tension before adding any tension to the other side. See? What you are doing is shifting the wire, very slightly, around the hitchpin and altering all the bearing points on the wire. It may help.....or it may induce more problems...so it's something to try before you bite-the-bullet and change the wire.

If the false beat is audible when struck by the hammer, I'd look to the hammer-squaring and string leveling. Have often found that lifting the low wires, and getting an even blow on all three strings, can remove some weird sounds. Better damper function, too!

As to why the left-string has more false beats? I have no clue whatsoever!

Sipping Costa Rican,
I am,
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Oregon Coast Piano Services
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#1986220 - 11/13/12 03:17 PM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
David Jenson Online   content
2000 Post Club Member

Registered: 10/22/06
Posts: 2180
Loc: Maine
I haven't noticed a preponderance of false beats on either the right or left, but if the left turns out to be statistically more problematic, might I suggest a political parallel? laugh


Edited by David Jenson (11/13/12 05:37 PM)
Edit Reason: pumped up the homor to full screech
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#1986272 - 11/13/12 05:05 PM Re: Why do left of tri-chords develop false beats more often? [Re: Supply]
Jerry Groot RPT Offline
6000 Post Club Member

Registered: 11/07/07
Posts: 6828
Loc: Grand Rapids Michigan
Originally Posted By: Supply
I have not found that the left string is more often false than the one on the right.


Nor have I. In fact, I have found the opposite to be true. The left string is quite often less false.
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#1986316 - 11/13/12 07:15 PM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Dave B Offline
1000 Post Club Member

Registered: 08/01/11
Posts: 1974
Loc: Philadelphia area
Just happy to be here in the middle.,,lol

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#1986325 - 11/13/12 07:44 PM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Emmery Offline
2000 Post Club Member

Registered: 04/02/08
Posts: 2481
Loc: Niagara Region, On. Canada
I haven't noticed false beating strings being in one place or another more than anywhere else on all pianos. Had a guy who worked in a factory explain to me once that when the string is installed, if care is not taken to wind the tuning pin so that the string is not twisted or even slghtely kinked when installed there is less likelyhood for false beating. He said that if a twist goes into the string which turns in a direction that wants to rotate out away from the bridge pin, false beats can occur more often also...especially if the downbearing is small.
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#1986375 - 11/13/12 10:30 PM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Supply Offline
3000 Post Club Member

Registered: 09/11/06
Posts: 3919
Loc: Vancouver Island, BC, Canada
Originally Posted By: Jerry Groot RPT
Originally Posted By: Supply
I have not found that the left string is more often false than the one on the right.

Nor have I. In fact, I have found the opposite to be true. The left string is quite often less false.
The OP is on the south side of the equator, so perhaps that has something to do with it??? wink
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Jurgen Goering
Piano Forte Supply
www.pianofortesupply.com

Piattino Caster Cups distributor

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#1986485 - 11/14/12 04:35 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Gregor Offline
Full Member

Registered: 10/31/08
Posts: 436
Loc: Münster, Germany
I defenitely found the left string beeing more false than the others, but only in the treble.

Gregor (North side of the equator)
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#1986650 - 11/14/12 01:30 PM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Rasmus Offline
Junior Member

Registered: 11/15/10
Posts: 8
Loc: Aarhus, Denmark
My experience is the same. More false beats in the left strings. I have given it a lot of thoughts and concluded tha same as rxd: "The speakinlg length bridge pin is nearer to the edge of the bridge giving a less secure termination."

Now, when we're talking abouth the small differences within the unisions; have you also experienced the right string to be more sensitive to humidity changes than the others?
In summer (humid) it's the highest of the three strings and in the winter (dry) it's the lowest. How come? It's the same for both uprights and grands.
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#1986673 - 11/14/12 02:36 PM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Ed Foote Offline
1000 Post Club Member

Registered: 05/03/03
Posts: 1228
Loc: Tennessee
Greetings,
Jim Ellis and James Arledge did some very interesting research on false beats,(it was published in the Jounal last year). They had a pair of terminations that could be rotated and indexed, and some transducers to record it.
They found that if the string was installed with it's natural curvature in the vertical or horizontal plane, there was no false beat. However, if the string's natural curvature was at 45 degrees to the blow of the hammer, there were always false beats.

My experience tells me that most of the false beats in pianos are due to wire damage or bridge termination. Now, when I find I have an untunable note, and it HAS to be fixed, I replace the string, and also check the condition of the bridge termination. The pin has to be tight, and the notch has to be even with it's centerline. Older bridges that have suffered indention will allow the final wooden termination to extend past the pin, so if necessary, I pull the pins, renotch so that the edge is at the middle of the pin hole, give a small shot of water-thin CA, and install new bridge pins. Then, I make sure that the wire's curvature is horizontal, (I use a dummy pin for installation, so I have control over the orientation of the curvature. It works about 80% of the time.

The other 20% I ascribe to some resonant frequency in the piano's structure that is causing the out of phase sound.
Regards,


Edited by Ed Foote (11/14/12 08:50 PM)

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#1987076 - 11/15/12 12:51 PM Re: Why do left of tri-chords develop false beats more often? [Re: Rasmus]
contrapiano Offline
Full Member

Registered: 06/04/12
Posts: 32
I almost always find that the right string goes sharp and left flat relative to the center as the humidity increases.

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#1987695 - 11/17/12 02:01 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Chris Leslie Offline
500 Post Club Member

Registered: 01/01/11
Posts: 720
Loc: Canberra, ACT, Australia
Thank you for the responses. I find the variety of contradictory opinions confusing.
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Chris Leslie
Piano technician
http://www.chrisleslie.com.au

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#1987717 - 11/17/12 07:19 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
Phil D Offline
500 Post Club Member

Registered: 01/15/10
Posts: 551
Loc: London, England
I find it confusing as well. I've noticed many pianos having false beats mainly on the left string, and have often adjusted my muting pattern so that I start on the right string of every note to get around this. Maybe it is down to the type and quality of pianos people are used to, or maybe some technicians have learnt better than others to ignore false beats.

On the pianos that exhibit this phenomenon, I usually find that the bridge is in poor condition. The seating of the bridge pins seems to deteriorate more quickly for the left pin on many pianos, which as rxd says is closer to the edge of the bridge.

I'm very surprised that there are people here who've never encountered this!

Originally Posted By: "Ed Foote"
The other 20% I ascribe to some resonant frequency in the piano's structure that is causing the out of phase sound.


I remember somebody saying a while back that they'd experimented with mass-loading the bridge to ameliorate false beats. It works by changing the resonant frequency.

(I bet the granite bridge is great for this! laugh )
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The Cycling Piano Tuner

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#1987784 - 11/17/12 11:45 AM Re: Why do left of tri-chords develop false beats more often? [Re: Chris Leslie]
daniokeeper Offline
1000 Post Club Member

Registered: 02/01/09
Posts: 1104
Loc: PA
I wonder if something as simple as "the odds" could also be a contributing factor. If you have 3 strings on a unison, maybe the odds of one of them having a problem is 3 times greater than on a single string unison smile Edit: For instance, instead of 2 termination points at the end of the speaking length on a single string, you now have six that have to be correct for a just one unison.

As for tuning unisons, I've simply given up on just tuning them once. I always tune them at least twice. Until I got an ETD, I never really appreciated just how much effect changing the tension on a single string could have on its brother strings in the same unison.



Edited by daniokeeper (11/17/12 11:48 AM)
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