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That is an observation. The theory will come along when you explain why you think this might be the case.

Del

Flat, as opposed to what? Are you talking about the size of the holes?

The plate is flat there, as opposed to being domed. Because of this, there is a lot of space between the top of the soundboard and the bottom of the plate, filled in with wood, either with "acoustic dowels" or blocks of wood. I think that dampens the effect of weight of the plate on the inner frame. This assembly method then absorbs more of the fundamental, dissipating it as motion this area, rather than reflecting it back into the soundboard.

BDB,

Two things confuse me about your posts. One that the Grotrian lacks fundamental, when others describe more fundamental in this piano than say a Steinway.

The second item is your statement about the dome section. Grotrian provides a mounting mechanism that specifically terminates the plate around the far edge of the soundboard to enable it to vibrate more freely (according to them). This would have the effect of reflecting energy rather than absorbing it.

Placing a large weight on top of a greater surface of the soundboard directly would absorb the energy.

I think any theory like this one or yours is meaningless to discuss without accompanying data (measurements).

There are many other things that will absorb energy (like duplexes and bridge designs).

It remains to be shown to me how absorbing energy would detract from the fundamental. In fact, the first vibrations to dissappear would be the higher frequencies. Therefore by absorbing energy I would expect the sound spectrum to shift to the bass. Not toward the treble.

It is very difficult to absorb low frequencies and not high frequencies. The most likely method that a scale designer would use to accentuate the first harmonic (as in a Steinway design) is by varying the hammer strike point, and the tension of the scale.

None of these pianos lack fundamental. The more accurate description is that the fundamental is stronger or weaker compared to the harmonics. What people say about these things is often much different from what is actually happening. If you recall from a few weeks ago, there were spectral images of a Steinway and a Bösendorfer where some people wrongly interpreted noise as more harmonics from the Bösendorfer. One of the interesting aspects of those images was that the fundamental of the Steinway was much more prominent compared to the harmonics than the Bösendorfer. If you can find that image, you can see that the height of the fundamental on the Steinway was much higher than the harmonics compared to the fundamental on the Bösendorfer.

The Grotrian I was working on was made in the mid 1950's and may be different from what you know.

I'm not actually talking about weight on the soundboard, more weight on the rim where the soundboard is glued to it. At least, I think so. The acoustic dowels, a couple of dowels on either side of the bolt holes on the plate, is what the plate actually rests on in the Steinways, Yamahas, and maybe others.

I realize that measurements are sketchy, but this has been the experience of my quite well-calibrated ears. In the case of the Bechstein E versus a Steinway D, there have been 2-piano concerts with them, and believe me, I compare them quite closely. You must realize that pretty much everything that is stated in these forums is done without measurements.

You don't live in earthquake country, so you might not know that taller buildings don't shake as fast as shorter buildings. The same is true of tuning forks, though. Smaller tuning forks are higher pitched than longer ones. If you have a mass on a tall stick, it will absorb more of the lower frequencies than the same mass on a short stick.

Steinway did feel strongly enough about the cupola frame to have it patented.

The height of the fundamental in the two images a couple of weeks ago is only dependent on the volume setting of the microphone preamp. You have to adjust the volume to equal level for the fundamental in the S&S and Bosey to know whether the relative magnitude of the harmonics is higher or lower. So I disagree that one piano had a larger fundamental than the other. We don't know unless we measure the overall volume of both sounds and know they are the same.

That being said, I did think of a way that the system could not reinforce the lower frequencies and that is by bridge design. If the bridge did not couple the first harmonic or fundamental to the soundboard as well as it did the higher frequencies then you could have a sound that "lacks fundamentals". That is the bridge decouples the low frequencies and therefore doesn't amplify them on the sound board as much.

I actually don't have a problem about discussing sound without measurements as this is still how high end audio is evaluated (ears seem more sensitive than equipment - go figure). The only issue I have is ascribing how this is achieved physically. It should be able to be done by measurement.

Not sure about your building analogy though. How does it play in to the plate theory? My understanding is that the plate is "inert" and the soundboard and strings are vibrating...

Thanks

Piano plates are not exactly “inert.” It might be better if they were but, being made of gray iron and not being either infinitely massive or infinitely stiff, they do vibrate somewhat in response to the vibrating energy from the strings. Some more than others depending on the specific design of the plate.

The rules governing this energy transfer (from the strings to the plate) are the same rules that govern the transfer of energy from the strings to the soundboard. That is, a very stiff hitchpin panel will be more resistant to low frequency energy and a very massive hitchpin panel will be more resistant to high frequency energy.

And, being made of a relatively low-grade gray iron which has excellent vibration damping characteristics, most of the energy that does end up in the plate is absorbed and dissipated as heat. It matters little whether this is ‘fundamental’ energy or ‘harmonic’ energy. Very little of this energy is transferred to the case or rim regardless of the plate mounting system.

About the only way to limit the amount of energy transferred to the plate is to make it more massive and/or stiffer in the area immediately surrounding the hitchpins. What is happening back at the rim is of relatively little consequence. The only effective ways to do this are to make the plate — at least the hitchpin panel — of a stiffer material (i.e., a higher-grade iron or steel), to make the hitchpin panel thicker or to couple the plate to some reinforcing structure (such as the bellybracing structure via nosebolts). This, by the way, is what the Steinway ‘bell’ is all about.

The claim of the ‘cupola’ shape to the plate casting is that this shape makes the plate casting stiffer. And if all factors are otherwise exactly equal this will be true. At least in terms of the plates’ overall 'static' stiffness. However, as with most things in life, all other factors are rarely, if ever, exactly equal. A piano plate designed to be flat — such as the Grotrian — can be made considerably stiffer than it really needs to be by the judicious use of nosebolts and it can be made equally resistant to vibrating energy absorption by making it adequately thick in the area immediately around the hitchpins and by placing the hitchpins well back away from the edge of the plate.

As well, a piano plate designed with a cupola shape can be made relatively flexible — especially in terms of its propensity to absorb vibrating energy — by making the area immediately around the hitchpins relatively thin or by placing the hitchpins closer to the edge of the plate.

In terms of energy transfer from the strings to the plate it is the region immediately surrounding the hitchpins that matters. In terms of overall flex and stability as a response to overall string tension the cupola shape may be a factor — but, again, only if all other factors are exactly the same and they never are. The piano manufactures making flat plates long ago — at least as early as the late 1800s — learned how to make them structurally adequate. Indeed, they learned this well before the cupola plate construction was patented. In my opinion the cupola plate patent, like so many other patents that look and sound so impressive on paper, contributes more to piano marketing than it does to piano performance.

As with most aspect of piano performance, the relative amounts of fundamental and harmonic energy in the piano’s sound energy envelope is depending on all of the many disparate elements that go into its design and construction. By the time we sort through the string scale, the soundboard assembly design and construction, the rim design and construction, the action and hammers, the importance of the shape of the plate panels has faded into the dark recesses of the hall closet.

Del

It's not really the shape of the plate that would matter. It's how high above the soundboard, or more exactly, the inner rim it is mounted. And it isn't the energy transfer of the strings to anything else that I am thinking of. It is whether the vibrational energy in the soundboard is reflected at the rim or absorbed. The more energy that is reflected back into the soundboard, the better. It's an impedence question.

In this model, what really matters is the amount of the plate rim bolts that is above the surface of the soundboard. They are going to transmit energy away from the soundboard and into the plate, or into friction rubbing against the plate, where it is pretty much going to die. The longer the bolts, the lower the frequency.

It is all about back to the reflectiveness of the rim. The more rigid the rim, the more energy goes back into the soundboard. I think that's what happens with M & H's tension resonator. Holding the rim tight around the edges increases the reflectivity of the soundboard. It would also explain why a soundboard that comes loose from the rim would have less sustain. And yes, a soundboard with no connection to the rim would have very good reflectivity at half the frequency. It would be hard to hold in place, though! It's all a question of impedence matching.

As for Grotriman's remarks about the images: If the spike at 440 htz is 40% higher than the spike at 880 htz, that would mean a greater percentage of fundamental than if the spike were only 20% higher. That's about the variation I was looking at. Admittedly, those images were probably not made with extreme accuracy, but there was enough to show that sort of difference, and it was quite evident to the eye.

Ah, I think see where this is going.

So, you’re thinking that the shorter the distance between the bottom of the plate and the top of the inner rim is a factor in tone performance? The shorter this distance the more fundamental energy there will be in the tone envelope?

Del

Yes, that's it. The shorter the distance, the more rigid the rim, and the less fundamental energy absorbed by motion in the plate and rim bolts and whatever else lifts the plate above the rim.

Well, maybe. Though I should think it would be way, way down on the list of things that might affect the sustain of any part of the spectrum. So far down, in fact, as to be virtually undetectable.

Del

* Grin *

My thoughts exactly Del.

Possibly. But I was once discussing soundboards with a physics professor, and he mentioned the importance of impedence. It should be possible to do some experiments simply using a drum.

Yes, impedance is important -- in soundboards, rims and plates. But how would you investigate this using a drum?

Del

I would take a heavy loop of steel or some such material and fasten it in various ways and at varying heights above the rim of the drum. If you hold everything else the same, you should be able to hear some interesting results. If you find, for instance, that the relative amplitude of the fundamental pitch of the drum changes, that could show the effect.

Just strapping a chopstick on a drum and moving a weight up and down on it might show the effect of resonance at various frequencies.

That may tell you something about drums but I don't see it telling you much about pianos. The principles of operation and construction are some different. The same problem exists with attempts made at comparing the violin with the piano. The differences in their structure and operation are simply too great.

Del

Perhaps. But it is cheap enough to try. If I get the time, maybe I will do it. At the very least, I could talk to some drummers.