http://de.yamaha.com/de/products/musica...sacoustic/

http://www.kawai.de/k500atx2f.htm

http://www.ncftitusville.org/music/?p=148

And don't miss part2, where he added a second large transducer for the bass:   

http://www.ncftitusville.org/music/?p=311

Unless I'm wrong, this guy posted in pianoteq forum some time ago, showing these same pictures.

I would like to know if anybody already played the Kawai CA93 or CA95, since these models use a real wood soundboard.  Is that possible to connect pianoteq to the sound imput and get a ok sound?

Picture of a transducer on the soundboard of Kawai CA93:

This model use soundboard with transducers and also speakers in unison with it.

This video of CA93 shows that despite the soundboard a video recorded by side the piano do not exactly make it sound as a video recorded by side of a upright, despite of get closer.
http://www.youtube.com/watch?v=vEuyjaOEaag

But I do want to hear the results. When there is time I may get two or three of these shakers just to learn what can be done.

I'm surprised that no keyboard company has come out with a model using these.

Here are some of my thoughts to your questions, in no real order:

If you are going to attach tranducers to a real soundboard, then I would suppose that they should go where the bridges connect with the strings -- not where the hammers are hitting the strings.

On ribbing and crowning: 
Ribbing is a structural engineer's way to make a relatively thin membrane ... rigid, and to initiate a crown to the soundboard.  The reason a soundboard is crowned, is such that it pushes towards the strings held in tension, and connected to the soundboard at the bridge locations.

Now, this is going to raise a troubling question for all of us:  If there are no strings "strung", which produces a downward force towards the crowned soundboard, do we need a crown at all?  Do we need ribbing at all?

EDIT:  An afterthought answer to the question of crowns and ribbing:  I have played a few Baldwin grands, whose octaves in C5 to about G6 sounded absolutely "dead" -- essentially many decibels less than the rest of the piano.  This is because the crown had sunken in this area, and the soundboard no longer made strong contact with the motions of the vibrating strings at the bridge.  Unless there is a specific place of contact for each note, i.e., 88 transducers, will only a few transducers leave a number of dead spots in the sound of the piano?  End Edit.

* * * * *

Upon standing back and thinking for a while, let's consider what function a soundboard is supposed to perform:
The obvious (but oversimplified) answer is that a soundboard amplifies the tiny movements of tensioned steel and copper-wound steel strings.  Something that is not so obvious is that the soundboard is aligned in such a way that its wood grains run somewhat parallel to the bridge.  This is because sound transmits with approximately five times more efficiency -- along the grains -- than against the grains.  We want to carry the sound of the treble notes ... towards the left, and the bass notes ... towards the right, to encompass the entire soundboard.

One may not be aware of this, but if you stand close to the treble side of a grand piano whose lid is open, and face yourself towards the strings -- you will notice that the treble notes' sounds seem to "originate" from all over the soundboard!!!

The best pianos, and the top-of-the-line pianos within a given brand receive the woods whose parallel grains number between 15 and 20+ grains per inch.  Pianos towards the lower end of a given brand's product line receive the "cheaper" soundboards, whose grain density numbers less than 6 or 8 per inch.  (Just last week, I tuned a horrible Wurlitzer baby grand (<5') whose grains, I swear, numbered less than 5 grains per inch.)

* * * * * *

Where does this discussion lead us?  Sorry to say, really don't know.

Consider this:  the strings' vibrations at the bridge do NOT have any reverb associated with them, at the outset.  If the transducers are placed by the bridge, as I had originally proposed, then the "knock" of the action's sound will be in the wrong place.  Worded differently, I am not so sure that playing a recording of a piano (or Pianoteq's audio output) to a soundboard is going to make the instrument sound more like a piano.  Resonance occurs IN the soundboard, rather than by feeding it vibrations coming already from a different soundboard.

* * * * *

At the outset, I believe you might consider the following:

Hopefully, you have a grand piano at your disposal.  I would suggest that you "wedge" a few speakers under the piano, and against the soundboard, and play Pianoteq (not the real piano) through those transducers.  (I believe you will become quickly disappointed -- but do persist and move the speakers around.

In my opinion, it's not worth talking about making your own soundboard ... as some soundboards on expensive pianos cost more than the price of a midpriced grand!  We're talking kilodollars/kiloeuros here.

My $20,000 worth.  (2 cents worth, adjusted for inflation.)

Cheers,

Joe

Mulling this over, I find myself coming up with questions:

1. What to try first--just buy some boards made from tone woods and experiment with the placement of the transducers?

2. How thick should the boards be to achieve the best sound? Will depend on the tone wood?

3. What about ribbing? Piano sound boards have ribs that contribute to the

4. And to approach a serious experiment, one would have to create a crown, yes? Seems as though one would have to recreate a real soundboard to make this valid.

5. Or just attach the transducers to a real piano's sound board. In which case, where should the transducers go? Near the hammer strike points?