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Mason and Hamlin AA Chladni low frequency #2857915
06/12/19 07:41 PM
06/12/19 07:41 PM
Joined: Sep 2018
Posts: 466
Chernobieff Piano Offline OP
Full Member
Chernobieff Piano  Offline OP
Full Member

Joined: Sep 2018
Posts: 466
I just made another video of a chladni pattern on a Mason and Hamlin AA. The natural frequency of the soundboard was 43hz. I'll make another video in the future of the same piano with a new board. I'll be aiming for a lower frequency.
I currently have 9 grands i'm rebuilding and i will be recording their soundboards frequencies. At that point, i believe i will have more data for comparison, that will be of much more value than the one on one off articles that are on line.

https://www.youtube.com/watch?v=aFbb1mzhx5E&feature=youtu.be

-chris


Maker of Fine Piano Soundboards
Chernobieff Piano Restorations
Lenoir City, Tennessee
www.chernobieffpiano.com
grandpianoman@protonmail.com
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Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2857990
06/13/19 02:12 AM
06/13/19 02:12 AM
Joined: Sep 2015
Posts: 2,007
Dublin
johnstaf Offline
2000 Post Club Member
johnstaf  Offline
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Joined: Sep 2015
Posts: 2,007
Dublin
That's fascinating. How much does the pattern change when the piano is strung?

Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2858064
06/13/19 08:31 AM
06/13/19 08:31 AM
Joined: Jan 2017
Posts: 706
Indianapolis
G
GC13 Offline
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GC13  Offline
500 Post Club Member
G

Joined: Jan 2017
Posts: 706
Indianapolis
This is very interesting Chris. Keep posting!

Re: Mason and Hamlin AA Chladni low frequency [Re: johnstaf] #2858214
06/13/19 02:48 PM
06/13/19 02:48 PM
Joined: Aug 2009
Posts: 308
C
Chris Storch Offline
Full Member
Chris Storch  Offline
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C

Joined: Aug 2009
Posts: 308
Originally Posted by johnstaf
That's fascinating. How much does the pattern change when the piano is strung?


The answer is "a lot". T. Moore and his students determined this in their interferometric studies of piano soundboards in 2006.

https://scholarship.rollins.edu/stud_fac/2/

From the Abstract:
"Deflection shapes are analyzed and compared to a finite element model, and it is shown that the force the strings exert on the soundboard is important in determining the mode shapes and resonant frequencies."

E-mail me if you'd like a copy of the full paper.


Chris Storch
Acoustician / Piano Technician
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2858332
06/13/19 06:53 PM
06/13/19 06:53 PM
Joined: Sep 2018
Posts: 466
Chernobieff Piano Offline OP
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Chernobieff Piano  Offline OP
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Joined: Sep 2018
Posts: 466
So the Moore study would be a different thesis than what i'm after. His study would be better titled " The effects of downbearing on a Vibrating Soundboard".
What i'm after is a tool that can test soundboards of many makers for comparison purposes, that explain why some soundboards sound way better than others.
After i do a sound test, and determine the resonating frequency of mode one. I don't stop there. I mic the entire board. I measure the rib scale. I weigh the soundboard, I observe it's behavior after being removed from the rim. I then run the data through my self made computer software.

For example, here are a couple of things i found out about the Mason and Hamlin soundboard. With boards of that size, the average weight is 15 lbs with bridges on. This one weighed 22.3 lbs. A lot of boards actually crown back up (apparently flattened by a poorly made rim). Others just stay flat. The MH actually had a decent crown in the piano while glued to the rim, but reverse crowned when removed. This tells me that Mason and Hamlins emc% procedure perhaps is faulty. It will be very interesting for comparison when i put one of my new soundboards in, it will feature a lightweight, low rib scale profile. Then i'll do the chladni test. Then rebuild the piano and listen to the results.

Next is a Steinway O. Should be in a couple days.


Maker of Fine Piano Soundboards
Chernobieff Piano Restorations
Lenoir City, Tennessee
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2858484
06/14/19 10:00 AM
06/14/19 10:00 AM
Joined: Sep 2018
Posts: 466
Chernobieff Piano Offline OP
Full Member
Chernobieff Piano  Offline OP
Full Member

Joined: Sep 2018
Posts: 466
Update:
I just went over the engineering of the Mason and Hamlin AA Rib scale.
The data is: (and shhhh don't tell Gene, this is top secret)

Original --- Modified
H/W profile 92% --- 78%
Volume unit .83 (in3) --- .75 (in3)
Rib to Panel Ratio 14% --- 13.8%
Bending Stress 622 p.s.i. --- 891 p.s.i.

In all parameters i was able to reduce mass, and bring the stress to an acceptable level. The soundboard should be about 5-7 lbs lighter and more than strong enough to last another cycle. I suspect with the reduction of mass, that the mode one frequency will be lower. We'll see. Thanks for all the interest!
-chris

Last edited by Chernobieff Piano; 06/14/19 10:01 AM.

Maker of Fine Piano Soundboards
Chernobieff Piano Restorations
Lenoir City, Tennessee
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2881841
08/20/19 09:39 PM
08/20/19 09:39 PM
Joined: Sep 2018
Posts: 466
Chernobieff Piano Offline OP
Full Member
Chernobieff Piano  Offline OP
Full Member

Joined: Sep 2018
Posts: 466
***The new board vibrated at the exact same frequency!****

This is an update to the Chladni Test on the 1902 Mason and Hamlin AA soundboard. The original soundboard vibrated at 43hz (see video on my youtube channel). Now here is what happened after the new board was installed.
It vibrated at the exact same frequency. Now here is why that is odd and has me slightly baffled. The original board was heavy at 15lbs, and the panel was a thick 3/8" with no tapering. The ribs were also massive.
The new board was 3 lbs lighter with a thinner panel and lower volume of rib stock. The original had Spruce ribs and the new board Used Eastern White Pine.
Anyone out there want to offer an explanation as to why the frequency was the same?
I have a theory, but I want to see what others think.
Thanks in advance.
-chris


Maker of Fine Piano Soundboards
Chernobieff Piano Restorations
Lenoir City, Tennessee
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2881876
08/21/19 01:31 AM
08/21/19 01:31 AM
Joined: May 2010
Posts: 107
Fort Worth, TX
N
Nathan M., RPT Offline
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Nathan M., RPT  Offline
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N

Joined: May 2010
Posts: 107
Fort Worth, TX
Could it be because the bridge (and of course the case dimensions) ends up being the main thing determining the fundamental frequency? Have you seen cases where it changes a lot with a new board?


Nathan Monteleone
Piano Technician / Rebuilder
PTG Registered Piano Technician

My pianos (in various states of rebuild):
- 1900 Mason and Hamlin AA
- 1911 J&C Fischer 6'2" grand
- 1935 Story and Clark vertical
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2881925
08/21/19 06:12 AM
08/21/19 06:12 AM
Joined: Sep 2018
Posts: 466
Chernobieff Piano Offline OP
Full Member
Chernobieff Piano  Offline OP
Full Member

Joined: Sep 2018
Posts: 466
Nathan,
This was the first time I was comparing frequencies between the old and new boards. My initial thought was that the case dimension would determine the frequency range, but that within that range, mass and stiffness would matter.
-chris


Maker of Fine Piano Soundboards
Chernobieff Piano Restorations
Lenoir City, Tennessee
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2881959
08/21/19 08:00 AM
08/21/19 08:00 AM
Joined: Feb 2017
Posts: 2,423
New Hampshire
P
P W Grey Offline
2000 Post Club Member
P W Grey  Offline
2000 Post Club Member
P

Joined: Feb 2017
Posts: 2,423
New Hampshire
This is pretty interesting.

Pwg


Peter W. Grey, RPT
New Hampshire Seacoast
www.seacoastpianodoctor.com
pianodoctor57@gmail.com
https://www.youtube.com/watch?v=PK0T7_I_nV8
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2882802
Yesterday at 03:58 PM
Yesterday at 03:58 PM
Joined: Sep 2018
Posts: 466
Chernobieff Piano Offline OP
Full Member
Chernobieff Piano  Offline OP
Full Member

Joined: Sep 2018
Posts: 466
So here's my theory based on observations of several soundboards of the same size. I think the fundamental frequency will be higher on a board when it is new. As the board ages and the compression diminishes, the frequency will also drop. Pretty similar to a timpani drum head when tension is released. So the MH AA was probably in the 50 hz range when new, and now that it is a hundred years old and the compression is gone the frequency was down to 43 hz. Therefore, I surmise that my new board which is starting at 43 hz, and will probably be down in the 30 hz range when it has aged.
-chris


Maker of Fine Piano Soundboards
Chernobieff Piano Restorations
Lenoir City, Tennessee
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency [Re: Chernobieff Piano] #2882903
3 hours ago
3 hours ago
Joined: Nov 2010
Posts: 5,718
Hobart, Australia
A
ando Offline
5000 Post Club Member
ando  Offline
5000 Post Club Member
A

Joined: Nov 2010
Posts: 5,718
Hobart, Australia
What about the fact that they are of the same size? That must be playing a role in them having the same resonant frequency? If the board were 10% bigger or smaller, wouldn't you expect a shift in frequency?


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