I stumbled upon this yesterday:
http://www.speech.kth.se/music/5_lectures/

Afterward I did a search here on "five lectures" and it is only mentioned a few times, mostly in the tuner-tech forum.

It is very interesting and informative reading.

Thanks for posting that. I will give it a read about the time I hit cup # 8 in my morning caffeine spree.

*edit*
Curiosity got me. In another thread, BDB was citing a theory about soundboard vibration. This part of the five lectures illustrates how a soundboard vibrates.

The way the are doing it, the board divides itself much like a vibrating string, higher frequencies producing more nodes.

Just remember that writing an idea down doesn't make it true. That goes for all of these lectures, and whatever anyone on these forums writes. It goes for what I write, too, of course.

(Chances are our opinions are actually our opinions. But that's about as far as it goes!)

These illustrations (called Chladni patterns) are best viewed with a certain amount of understanding and background. They do have some limitations. They were taken on a soundboard that was not glued to the rim of the piano — it was simply screwed down. There were no bridges glued to the soundboard. And, finally, there were no strings in place, hence no string bearing and no soundboard loading. All of these would have significantly altered both the frequencies of the various resonances and their vibration patterns.

An aside: there is one statement on this page that is in error. Mr Conklin states: “In general, the thicker the soundboard, the louder the piano but the less the duration of its tone.” The opposite is true: All other factors being equal a thinner soundboard will give a louder initial tone but a shorter sustain time. The thinner soundboard panel will have less mass and the system will be less stiff. Therefore it will accept energy from the strings at a faster rate giving a louder, more percussive attack but — since the available energy from the strings will be dissipated at a faster rate — a shorter sustain time.

Del

True. But some opinions are based on actual tests, measurements and observations.

Del

Now I will read the lectures with Del's caveats in mind! Del, do you have any other observations to make about these "lectures?" If they are basically sound (pun intended), perhaps Frank should put a link to them in the FAQ section along with any amendments from Del.

David F

Thanks, Del, for pointing out that error.

I agree with piano*dad that it would be good to have a link along with amendments to correct mistakes, address how advances of the last 15 years affect the material presented, etc.

They are basically very sound. It’s good research and the lectures tell us a lot about how the piano and the piano action works.

It is just that the research backing up several of these lectures was done on specific pianos -- in some cases relatively small pianos. It is unwise, I think, to make generalizations applying to all pianos based on what is observed and measured on one size and type of piano. Some of the soundboard experiments were conducted on a fairly small vertical piano back, for example. The results of some of those tests would have been quite different had they been conducted on, say, a 52” vertical or a concert grand. It is likely that some of the conclusions would also have been different. Which doesn’t make the information incorrect. It is based on solid research. But there is, I think, a tendency toward, “I measured this and got that result therefore that is how pianos works.” Rather than, “I measured this and got that result on this type and size piano therefore that is how pianos of this size and type work.”

Del

This is exactly the way I think a piano soundboard doesn't work. It's more the way a drumhead works, and a drumhead has resonant frequencies at various pitches, which, as Del correctly states, is not desirable in a piano. The ribs and crown keep the soundboard from working in that way. They add extra rigidity.

If you made a flat soundboard, especially without ribs, I would predict that the sound would have less sustain and less power, and would be uneven from note to note. While it would be louder than a string without a soundboard, the power would go into making the soundboard move in these patterns, which would generate a lot of heat mechanically, rather than reinforcing the energy as sound.

During one of the earlier times these were posted I listened to some of the sound examples. The one that impressed me the most involved longitudinal vibrations at different frequencies from the transverse (usual") vibrating mode.

Listen to Yankee Doodle in longitudinal mode (same transverse pitch).

The ribs and crown unfortunately do not prevent spurious soundboard resonances. With the bridges glued on, the soundboard assembly glued to the rim and with a string load the resonance patterns are similar but are broken up by the bridges. The fundamental resonant mode is at a higher frequency and there are still numerous miscellaneous resonances splattered over the frequency spectrum in which the soundboard typically operates.

One significant difference is the appearance of nodes and anti-nodes developing on opposite sides of the bridges. That is, one part of the soundboard will be going up while another part is going down at some resonant frequency with the acoustical result being simply a trading of energy back and forth from one spot to the other. This is especially problematic through the tenor section and has lead to the soundboard cutoff bars sometimes used to eliminate the forward bass corner of the soundboard. (The soundboard panel may still be there but it is non-functional.)

Del

Yes, you can't really eliminate any one particular element. The best you can do is try to minimize the undesirable ones and maximize the good ones. That's why there's always an element of art involved.

I wonder what the reactions would be by some of the world's best piano designers and makers reading here.

Suggestions:

"Ach Du Lieber" ....."WOW - I'll be damned" ....

..... "YAWN!!"[/b]

Actually, Norbert, one of the better designers and makers is "posting" here at PW. Lots of rebuilders have listened and are putting out some phenominal pianos. This is either because they are not afraid to try something new or they are convinced that old methods are less than desirable. The best pianos today are very often the pianos being remanufactured in small shops by innovative technicians. The manufacturers would be wise to listen up and try some of the principles being discussed on various piano forums and being shown at conventions and seminars by these rebuilders.

Once discovered, scientific principles cannot be unmade, no matter who doesn't bother to learn and apply them.

It's not art. It's science.

Dale

If you're running a business that has a reputation going back 150 years or more, you will be exceedingly cautious in making changes to your product. Look at what happened with Steinway and the Teflon(R) bushings!