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Hi Kurtmen,
Actually this statement is not correct. A couple of years ago, i made what i call a variable vibrating rib ( the stiffness is adjustable). By imparting the same energy into it to make it vibrate the stiff rib will vibrate a FAST frequency but SHORT duration. Then after adjusting it to be flexible, the same energy input made the rib vibrate SLOW and LONGER. Thats why the old Axiom among instrument makers was to get a lower tone for more warmth and depth. That gets lost with too much stiffness.
-chris

Hermerik,

So I sliced a soundboard between all the ribs to be able to mic the thickness easily.
http://chernobieffpiano.com/wp-content/uploads/2018/10/stieff-soundboard-007.jpg

Then I measured the thickness at many locations and drew a map.
http://chernobieffpiano.com/wp-content/uploads/2018/10/stieff-soundboard-thickness-pattern.jpg

By chance i noticed that the pattern looked proportional somehow.
Then I remembered the Golden Ratio.
So I made a quick drawing and laid it out the normal way. Then I drew ellipses using the top edge and other key points. And lo and behold it's almost exactly the layout of the thickness pattern of the Stieff board!!
Anyways, I thought it was interesting.
http://chernobieffpiano.com/wp-content/uploads/2018/10/Golden-ratio-thickness-pattern.jpg

-chris

Hi Chernobieff,
You are too focus in demonstrating your "perspectives" or "knowledge"
You picked a part of the text but not really understood the over all post
This is something really basic, it is just a simple partial-explanation about why ribs are placed on soundboards, versus having a board without ribs.

I don't know why you decide to attack me personally by trying to infuse what you think my motives are, and not address the issue i raised. I actually understood your post, and agree that the ear is the final arbiter. My point is that you made an error on fact. Here's another one, you said stiffness increases the efficiency of sound radiation, and the ribs job is to add stiffness. Then why not make them out of maple? On that scale maple isn't that much heavier as to be unreasonable.
Thanks,
-chris

Well you are taking stiffness as a factor without variables and degrees. Stiffness is absolutely required as well as flexibility, that's is the whole point the balance between the two.
This is why I felt you had no interest in anything, except in what you have to say. I spoke of stiffness as a required element but not the only absolute function of a rib or specification of a soundboard.

How about hickory? High strength to weight, lots and lots of twang.... ? And it's specifically American -- the last ice age killed off the hickory in Europe because the mountains there go East-West instead of North -South, so the trees couldn't seed ahead of the glaciers.

John,
I like where your going with this, but i think Ash has the highest strength to weight ratio of the hardwoods if i remember correctly. Great to work with too, machines very well.

Kurtmen,

My philosophy is simple. To learn all the different prevailing ideas( past and present) in piano technology (soundboards specifically) challenge the ones that are false, agree with the ones that are true ( for confirmation) learn of the current trends, to be well rounded. So i am absorbing what is useful and discarding the rest. It's my "Jeet Kune Do".
I've been talking flexibility in soundboards for years and everyone else talks only about stiffness like its an automatic reaction. Yet they never mention about too much stiffness. If i'm lucky and press them hard enough then i get the "impedance matching" thing. That's been the jist of conversations of the past 2 years. But all that theory stuff is fine, but i never hear any practical ways to pull that off. It just sounds like hit or miss and trying to sound intelligent while guessing.
So, care to throw in what you think the variables and degrees are? So when in the shop hovering over a newly installed soundboard, how do you know if its too stiff? Or too flexible? Where is the balance point?
-chris

One would find ribs made from hardwood way too "creepy". Sugar pine and spruce are extremely resistant to warping once properly seasoned and worked.

The "purpose" of making a soundboard "properly" stiff is to make it capable of responding with a broad range of the lowest modes that are not too far separated in frequency. This makes for even frequency response. Also one doesn't want the board to respond in multiple areas to the same frequencies until one gets high enough in the frequency range. Otherwise you could get significant phase cancellations.

The soundboard may not be the only part supporting sound formation. Here is an excerpt from Bösendorfer's web site.

Contrary to all other manufactures Bösendorfer constructs instruments concentrating on the use of spruce. More than 80% of this wood, ideal for instruments, can be found in Bösendorfer pianos. Verysimilar in principle to a violin the whole body - not exclusively the soundboard - supports sound formation. The actual core of the piano rim consists of a 10 mm quarter-sawn piece that is specially grooved by our craftsmen to allow it to be bent to the silhouette around the inner rim – this is unique to Bösendorfer. When a note is played, the integrated spruce components become acoustically active, forming a complete resonating body that allows the whole instrument to project your play. For outstanding richness of tone colour and our legendary pure and brilliant sound. This complex construction is part of the Viennese tradition of piano making.

Steve

Understanding soundboard response is very complex. It is too large to act like a piston, which, by the way is how speakers ideally behave. Additionally, the very stiff connection between the soundboard and the rim also inhibit its motion. Also, of course, a soundboard is not isotropic--its stiffness is different in different directions and different positions. Motion cannot be transmitted instantaneously--it travels typically in transverse or compression waves. So, when string movement is transmitted to the bridge it radiates outward with finite velocity until it is damped out or reflects off the rim. A soundboard has a fundamental (lowest) resonance. Below this frequency its ability to radiate sound becomes increasingly reduced (by the square of the ratio between the resonance and driving frequency). Honestly, to sort this out analytically seems impossible. Finite element analysis seems the best way to model and understand soundboard parameters. This is not a problem for large companies, though smaller ones likely wouldn't want to purchase the pricey software, and wouldn't want to pay a consultant to do the analysis.

I was never sold on the Bosendorfer "story" . It's so carefully worded as to not say anything factual that could be scientifically questioned. Even the violin comparison is questionable. The top plate and back plate are tuned to non-competing frequencies. The back plate is maple not spruce. So maybe the Spruce in the vienna construction method is holding back not enhancing sound production. Perhaps a backframe made out of ash or maple would be superior, not inferior.
The complications that would arise from beam frequency being in phase with certain notes. Do they tune beams to create a mismatch?
-chris

The "newer" Bosendorfer scales such as the 6'7" and 5'8" have verticaly laminated rims. That indicates to me the designers knew that these types of rims were structurally more desirable, and that with the older scales the company didn't want to invest the money to reformulate them for a laminated rim design. The sales people then took a negative and claimed it was a positive.

Ed, Wrong! You should go to Vienna for a tour of Bosendorfer before you tell people how Bosendorfer does things. What do you suppose is under those "vertically laminated rims" you are talking about? I've been on tours there 4 times as part of the master classes I have taken and have seen them produce rims just as they describe on their web site.

Steve

Chernbieff, really? Don't buy a Bösendorfer and you can go on believing your own story as much as you like. What story do you tell people when they want to buy a piano from you're company?

Lakeviewsteve,
I can see from looking at the pianos that the rims are continuous laminations and that there are no corner joints in the case of the smaller Bose grands. The big scales have angular corners showing a pieced up rim.

Lakeviewstiff,

Maybe you could offer a counter to the points i made, instead of a personal attack?
-chris

Bösendorfer rims were kerf-bent. I do not know whether they still are. I have seen a kerf-bent rim on a Knabe.

Only the outer rim is kerf-bent, a horrendously labour intensive process the inner rim onto which the soundboard is attached is made of segments of spruce, and more recently in the VC series, reinforced with some hardwood for greater rigidity. I was informed of the last bit of information from someone at Yamaha.

What do they mean by "vertically laminated"? Do they mean that the grain runs vertically rather than horizontally? That wouldn't be nearly as strong, but then again we're not supposed to play bumper cars with grand pianos....

No, that's ok. Personal attack? You don't know what you are talking about. End of Story.