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Mason and Hamlin AA Chladni low frequency
#2857915 06/12/19 07:41 PM
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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


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
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Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2857990 06/13/19 02:12 AM
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That's fascinating. How much does the pattern change when the piano is strung?

Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2858064 06/13/19 08:31 AM
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This is very interesting Chris. Keep posting!

Re: Mason and Hamlin AA Chladni low frequency
johnstaf #2858214 06/13/19 02:48 PM
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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
Chernobieff Piano #2858332 06/13/19 06:53 PM
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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.


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2858484 06/14/19 10:00 AM
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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.

Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2881841 08/20/19 09:39 PM
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***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


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2881876 08/21/19 01:31 AM
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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 / Amateur 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
Chernobieff Piano #2881925 08/21/19 06:12 AM
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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


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2881959 08/21/19 08:00 AM
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This is pretty interesting.

Pwg


Peter W. Grey, RPT
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Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2882802 08/23/19 03:58 PM
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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


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2882903 08/24/19 12:00 AM
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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?

Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2882965 08/24/19 09:18 AM
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That makes me remember Yamaha’s ‘Acoustic Resonance Enhancement‘ which apparently produces some benefits of aged wood but with a new soundboard. Does anyone know what Yamaha actually does with that?

Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2883041 08/24/19 02:25 PM
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Ando,

How you explain that I have observed the same size piano ( 4 Steinway M's) in which the boards had different frequencies using the same testing set up?
I think that shows what I said earlier about the size not alone being a factor.


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2883092 08/24/19 06:00 PM
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Originally Posted by Chernobieff Piano
Ando,

How you explain that I have observed the same size piano ( 4 Steinway M's) in which the boards had different frequencies using the same testing set up?
I think that shows what I said earlier about the size not alone being a factor.

That's kind of my point, size could be one of many factors, without being a sole factor. When you have a lot of factors influencing the final result, it's hard to separate them out. You have to make sure only one thing changes at a time for each experiment if you want to isolate factors. But surely dimensions are one of the primary factors that go into any soundboard's eventual resonant frequency.

Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2883099 08/24/19 06:31 PM
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Ando,

What are the many factors that you are referring to?
-chris


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2883574 08/26/19 09:00 AM
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Chris,
On those four M's, did you notice any relationship between the boards' thump tones and their resonant frequencies?

Craig


Craig Hair
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Re: Mason and Hamlin AA Chladni low frequency
Craig Hair #2883786 08/26/19 07:19 PM
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Craig,
Can't say that I have been looking for a relationship there. My focus has been on achieving a deep resonance on a glued in stand alone board. Versus resonance appearing after the plate mass is installed.

-chris


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Mason and Hamlin AA Chladni low frequency
Chernobieff Piano #2884648 08/28/19 10:48 PM
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Comparing the stiffness of each rib in three different Mason and Hamlin AA's. The left one is an original, the middle is mine, and the one on the right is a fellow competitor rebuilder.

The original is rather uneven, and so is my competitor's. And I was impressed that he kept the flexibilty in the bass. Usually too much stiffness is built in on rebuilds today. I have noticed that when I smooth out the stiffness that it seems to allow the piano to sing so much better.
Important!

http://forum.pianoworld.com//gallery/42/medium/11902.jpg


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
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