Piano World Home Page Forums Our Most Popular Forums Piano Forum How do the frame and case affect the tone of a piano?

The other day I came across this in Piano Price Point: Researching piano rims:


I can see thicker beams help but is a thicker rim better for a grand? Think Bosendorfer at 3/4"-7/8".

What about the case of an upright?

Greetings,
It is more than a question of mass, otherwise piano makers would make rims out of concrete. The case of a piano is entrained, i.e. it vibrates along with the string because the energy of the string moves the board and the board and ribs are connected to the case. The case not only receives, it also delivers, since the entrainment works both ways. If the board is connected to the case and the case vibrates, the board's vibration will be affected by the case vibration. Chickering built a number of pianos with the soundboard connected to an inner rim that was only connected to the outer case via a joint at the lower edge.

This has been understood by luthiers for a long time. If you change guitar tuners to a heavier set, the sound of the guitar will change. I think it a question of impedance, but Del Fandrich can shed more light on this that most anybody around here......
Regards,

Thank you, Ed.

Entrainment (I see the word has been adopted in many areas including psychology) would explain much of the background sound of a piano. That is sound other than fundamentals and partials.

Presumably piano makers arrived at their designs by trial and error as well as copying each other. Hence differences in rims.

Del has experience of this as you say ...

I am currently rebuilding a SS moderl B from about 1905. It has a stunning ability to vibrate the entire case structure as well as the plate. I noticed this potential when we were working on the soundboard and made a prediction verbally that this was going to be an awesome instrument. It is turning out to be such. Of course I don't attribute it to much of anything we did, just that it was awesome on day one (would have loved to hear when it was new...WOW!).

They don't all come out this way. I have detected various degrees of rim excitement in good grands. I suppose the possibility exists in an upright but probably to a somewhat lesser degree.

Vibration is the key. Interestingly, this B also appears to have two distinct resonant frequencies inherent in the structure. One at "C" and one at "F". One in the "unplated" structure (SB and rim alone) and one in the plate itself. Whether this is having any bearing on the matter I cannot ascertain (usually distinct resonances cause a problem but in this case not so far).

Rim construction choices (to me) simply contribute to the characteristic sound of each specific maker. They have different philosophies on the matter...some like it, some don't. I can come to like any of them as long as they're "good". 😁

Peter Grey Piano Doctor

I recently wrote in another thread clarifying info about Bösendorfer's inner vs. outer rims. The 3/4" you see is the outer rim, but the total inner & outer rim on a Bösendorfer is far thicker than average at 4.325" (I was measuring 7' grands). By comparison, the total rim (inner & outer) on a Yamaha C6 is 3", but the visible outer rim is thicker at ~1".

The optimal thickness of a rim is determined by quite a few variables, so thicker does not automatically equal better, though in some lower price point instruments, an obviously thinner rim can be a cost-cutting production measure, just like a fixed music desk or plastic fittings or a lid that isn't beveled. In a higher level instrument, I have plenty of reason to believe that the thickness is optimized to a variety of performance and durability standards, though I have accused Mason & Hamlin grands of being "overbuilt" . Certainly, there is a lot of research that suggests rims could be significantly smaller on smaller grands if other design aspects are changed to match. I believe this was a driving force in some of Del Fandrich's designs.

I've not studied upright rim construction to anywhere near the same level as grands, but one particular upright back design has struck me as superior in larger uprights. The "star back" design, made famous by Grotrian and famously copied in Yamaha's UX-series uprights seems to have real performance benefits, but also higher construction costs. If I locate photos, I'll share.

Yes, I had a UX3 myself and the design is interesting. It seemed to me likely to be much more rigid and, due to the fabricated ply construction, much more dimensionally stable when humidity changes. I presume it is also likely to have (for good or ill) an effect on the sound as you are replacing a series of solid posts with a more resonant structure, but I did like the piano as a whole however the result was achieved :-)

I wonder about projection too. Maybe it is my imagination but it seems to me that some grand pianos project the sound directly at the position of the player, more than others do.

Being a practical piano maker i try to avoid theorizing and prove things in a shop setting. Its quite often scientific theories have no practical value. One of my mentors had a wonderful analogy. He would compare the sound a wave makes when it crashes on a beach versus when it crashes against a pier. One is a soft crash and the other has a slap sound.

Some observations after putting in a new soundboard:
In heavily braced systems the soundboard will sound like a drum. When the plate is put back in, the tone of the soundboard changes to a higher pitch.
The sound is more strident when the bracing touches the spine.
In no-brace systems the board has no significant tap tone until it is strung.

And non of the above observations matter too much, if the downbearing is improperly set, and if the hammers are not voiced properly etc., etc.

-chris

Bösendorfer is the only manufacturer that uses a solid piece of spruce in their rims, it is carved in such a way it can be bent to fit their mold. The resulting spaces are filled in with spruce shims. They feel this extends the sound board in a way and yields sound and resonance improvements. I’ve seen this process in their factory. They apply an outer veneer and an inner veneer completely covering up the spruce. They said other manufacturers use several layers of veneers but nothing solid. Read about it on their web site.

So what does this mean for the piano enthusiast? Does it explain why one brand of piano “sings” to us and another quality brand of the same size doesn’t? I’ve only gotten to play two different Bosendorfers at different times at the Yamaha dealership. I found both to be exquisite. Is it the unique rim structure? Is it the overall build quality with the unique rim?

I do enjoy the technical discussions, so thank you.

So what does this mean for the piano enthusiast?

Tone and timbre.

Ed Foote has given a great description of the soundboard and the way the soundboard and the rim exchange vibrations. When the pianist strikes a key it sets the whole piano into vibration as well as exciting the strings.

Peter Grey refers to the resonances of a wonderful c1905 Steinway B while Sam Bennett refers to the need for a massive inner and lower rim. The dimensions of the Bosendorfer rim Sam gives happen to coincides with those of my 1905 Ibach. The beam at the bottom right of the Estonia photo seems to be cut to accommodate a wider lower rim too. Is that so?

Gwing suspects a radial arrangement of the beams may result in a more resonant structure (Steinway grands?), while stemPianist wonders about projection, and Steve comments how Bosendorfer aim for resonance in their rims with solid spruce construction. Perhaps Bosendorfer helped to focus the Yamaha SX series engineers on the resonances of the rim, not to mention pure wool hammers.

Chris C says, in other words, that a piano is the sum of its parts as well as well the skills that go into assembly and prep. I think his main point may be that no technical analysis will predict exactly how an instrument will sound.

Going back to Ed Foote's point the vibrations of the strings, the bridge and the soundboard, on the one hand, and the vibrations of the rim, the frame and the plate, on the other hand, feed each other at the rim.

At least that what I have gleaned from this thread.

Just to be clear, my comment was in the context of *upright* frames not grands, and the reason I suspected it might be more resonant was not because it was radial construction but because that particular construction, although incredibly rigid and stable, essentially formed massive hollow plywood box structures that seemed likely to be more resonant than solid spruce beams.

I don't even know if the resonance of a piano case is good or bad, or whether it could be either. I suspect it would be interesting to listen to a piano that managed to completely isolate the soundboard from the case/rim so that we were listening to the 'pure' soundboard, and also to listen to one that had a damped but inert case to prevent it colouring the sound.

Just to be clear, my comment was in the context of *upright* frames not grands, and the reason I suspected it might be more resonant was not because it was radial construction but because that particular construction, although incredibly rigid and stable, essentially formed massive hollow plywood box structures that seemed likely to be more resonant than solid spruce beams.

I don't even know if the resonance of a piano case is good or bad, or whether it could be either. I suspect it would be interesting to listen to a piano that managed to completely isolate the soundboard from the case/rim so that we were listening to the 'pure' soundboard, and also to listen to one that had a damped but inert case to minimise acoustic feedback and hence colouration of the sound.

@gwing, I had taken your comment together with Sam Bennett's about the Grotrian star back copied by Yamaha. As it happens I have a mental image of the Grotrian in mind and did not know about Yamaha's hollow construction.

Ed Foote mentioned Chickering built some pianos with the soundboard and the inner rim as an internal unit, presumably an attempt at the purer sound you mention.

The back construction of 52" Grotrian G-132 Concertino


The back construction of 52" Yamaha UX3


Certainly not identical, but you can see the inspiration of the design.


Because Bösendorfer's rim is made of spruce, not a laminated hardwood, it is essential it be massive as part of its design. Your Ibach from 1905 may have more in common with Bösendorfer's current designs than with other modern pianos, and I recall seeing other European makers later change from multiple-piece, solid rims, to continuous, multilamination rims.

Thank you again everyone. So there is quite a bit of science involved in piano design and construction. It’s not just a bunch of sales hype and blather.

Thank you for the Grotrian and Yamaha upright back shots. I see Yamaha appear to have a squeezed in a bit more soundboard area

Here is a shot from 1920 of an Ibach rim forming press. Is this a "multiple-piece, solid rim" construction? Would anyone know what the vertical white strips and the black strips at top and bottom might be? The position of the white strips seems to coincide with the clamp guides.

Photo 7 of this ad for a vintage McPhail upright shows its backframe:

https://youngspiano.com/product/mcphail-upright-serial-55036-1915/

And many Mason & Hamlin uprights have their upright tension resonator.

Steel backs rods? That is unusual surely?