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Diaphragmatic sound board decal on 1925 Steinway Model L
#2890508 09/15/19 02:38 AM
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There is a decal that says "Diaphragmatic Soundboard Reg U.S. Patent Off" on my 1925 Steinway L, which is odd since that was not introduced into 1936 – see photo [img]https://drive.google.com/open?id=1-YnJMvcOreCEY7jiglVZwcYGqO-BhV4G[/img].

Since I have some sustain issues with my piano (see separate thread), it seems unlikely to me that the board was replaced, and probably more likely that some overzealous restorer stuck it on when the piano was re-strung at some point. None the less, I would like to see if I could get positive verification.

I enquired with Steinway about the known history of the piano, and they told me it was sold to someone in New Jersey in March 1925, and was returned to the factory in 1963, but apparently they have no record of what was done. Given that it HAS been returned to the factory, I guess it COULD be possible that the soundboard was replaced by Steinway.
A few qns :
1) Is anyone familiar with this particular decal? Is it even a decal that was actually used by Steinway on their new pianos (or perhaps restored ones??), and if so any idea when it may have been used?
2) If the soundboard WAS replaced with Diaphragmatic version in 1963, does anyone know if Steinway would normally have recorded such a major piece of work? If it was, I can't imagine why they wouldn't record that for such a major piece of work.
3) Is there any way I can tell if the soundboard has been replaced? Does the diaphragmatic version have any unique characteristics with which it can be identified? Are there any tell-tale signs that I might look for on the piano that might indicate it was replaced?

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Re: Diaphragmatic sound board decal on 1925 Steinway Model L
PianissimoMe #2890605 09/15/19 10:07 AM
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The Patent process isn't overnight and immediate. Hope that answers your question.
As I stated in your other post. The poor rib structure and thin panel is the source of the sustain problem in your Steinway. Plus Steinway usually placed a heavy load up in the treble compounding the problem. Check the thickness of the soundboard in the top nosebolt hole. In most other high quality pianos that would be near 3/8"- thick, but in the diaphramatic board its closer to 1/4"+ thick. That's a problem for the second section (weak octave area).
-chris

Last edited by Chernobieff Piano; 09/15/19 10:13 AM.

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Re: Diaphragmatic sound board decal on 1925 Steinway Model L
PianissimoMe #2890762 09/15/19 08:10 PM
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If the piano was returned to the factory, it probably got a new soundboard then. If you post a picture of the decal, that might help because they have had slightly different looks over the years and I might recognize it as what was used in the 1960's. Steinway would not likely put the decal on a board that was not diaphragmatic.


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Re: Diaphragmatic sound board decal on 1925 Steinway Model L
PianissimoMe #2890854 09/16/19 06:16 AM
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Thanks Ed - I put a link to the photo in the original post. I tried posting the photo in the gallery. Here is the link Picture of decal I hope that works.

DO you think it is likely/normal(?) that Steinway would NOT have recorded replacement of the soundboard if they had actually done it?

See next post where I reply to Chris. Soundboard thickness sounds like it might not tally with diaphragmatic.

Re: Diaphragmatic sound board decal on 1925 Steinway Model L
Chernobieff Piano #2890875 09/16/19 07:34 AM
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Originally Posted by Chernobieff Piano
The Patent process isn't overnight and immediate. Hope that answers your question.
As I stated in your other post. The poor rib structure and thin panel is the source of the sustain problem in your Steinway. Plus Steinway usually placed a heavy load up in the treble compounding the problem. Check the thickness of the soundboard in the top nosebolt hole. In most other high quality pianos that would be near 3/8"- thick, but in the diaphragmatic board its closer to 1/4"+ thick. That's a problem for the second section (weak octave area).
-chris


Hi Chris - I checked the web and also other posts on this site, and it seems to be very consistently presented that diaphragmatic soundboard was NOT used until the mid 1930's - patent lodged 1935 and granted 1936.

As regards thickness of my soundboard, I measured the following at the nose bolts holes :
0.345" each for the two on the far left of the frame on the base strut (see photo of piano in the link in previous post, where you can especially see the location of the lower bass strut bolt in case not familiar)
0.34" at the tenor side nose bolt, and 0.36" for the treble side. Note this was a little tricky to measure, (using a bent piece of wire poked through the hole and marked with a felt pen from underneath) - so overall I would say all four holes measured the same.

According to Steinway website, the board should indeed be around 9mm/0.35" in the middle/apex of the crown, tapering to 6mm/0.24" at the edge, as you indicated. Using the actual patent diagram as a guide, the thickness at treble plate bolt should be around 20% of the taper less than the tenor one - which is only 0.023" and not viable to measure with my low precision measurement method, noting that the treble one was measured as 0.020 thicker. I think the most telling measurement though is the lower bolt on the base strut - it is only 5" from the rim and has NO taper compared to any of the other three, whilst I would estimate from the patent diagram, that this measurement should exhibit it lease 80% of the taper. It would therefore appear that my sound board is NOT of the diaphragmatic/tapered type.

Re: Diaphragmatic sound board decal on 1925 Steinway Model L
PianissimoMe #2890946 09/16/19 11:37 AM
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A close up inspection of that decal (from the first photo you posted) appears to me like a non-authentic decal. There is also what APPEARS to be a soundboard shim behind it. Cannot tell for sure from this distance, but if so it would be circumstantial evidence that it is the original board, with some "deception" added at a later time.

Maybe I missed it but what documentation shows that it actually went back to the factory in 1963?

Edit: What size are the tuning pins in there right now? .282"....286"....292", etc.

Pwg

Last edited by P W Grey; 09/16/19 11:39 AM.

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Re: Diaphragmatic sound board decal on 1925 Steinway Model L
PianissimoMe #2891258 09/17/19 09:48 AM
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No there is no sound board shim, but as above thickness of soundboard seems to confirm it is not diaphragmatic version.

I got history of my piano from steinway second hand department, saying it came in for repair in 1963. They were very helpful, albeit with the little that they had. They were of the belief the decal was "genuine".

Tuning pins are 0.292 measured on the diagonal - if that the correct way to measure them(?)

Re: Diaphragmatic sound board decal on 1925 Steinway Model L
PianissimoMe #2891291 09/17/19 11:26 AM
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Love that mahogany case. Looks factory original to me from early 1960's.

One more thing to check. In the top treble section inspect the joint between the soundboard edge and the reinforcing strip with screws. If it is a 45% angle, chances are it is a board done at the factory. There was only 2 or 3 independent rebuilders installing new boards in the USA at that time, if my information is correct.


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: Diaphragmatic sound board decal on 1925 Steinway Model L
PianissimoMe #2891319 09/17/19 12:20 PM
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If the pins are .292" they are 4/0 pins. I would suggest that it got restrung at the factory with no new soundboard. My reasoning that it's a fake decal is: look very closely and compare the bottom of the decal with the top. The bottom has rounded corners (like it should) but the top appears to be cut straight across with sharp corners (as if it was cut from a sheet...poorly). Also the degree of oxidation on bridge pins looks more like 1925 than 1963. If the SB had been replaced in 1963, so would the bridges. Doesn't look like it to me.

I could be wrong...I was wrong once 😁

Pwg


Peter W. Grey, RPT
New Hampshire Seacoast
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