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For the key length (and hence, key movement) aspect, I guess there are two aspects:

a) How long, in absolute terms, do the keys have to be for a human to play very advanced material?

b) How long do the keys have to be in order for a concert pianist to be able to easily switch between a concert grand and the other keyboard, that has shorter keys?

I.e - perhaps the key lengths in an upright are ENTIRELY adequate, and the only reason they are longer in a large concert grand is simply because they HAVE to be, in order for the pianist to be able to have enough leverage to play loud enough.

Greg.

Greg,

Hammers are usually placed at 1/5 to 1/7 of string length.
They are placed this way that the 7th harmonic is almost surpressed.
Thats another reason for the keys being longer.

For a nine foot the keys are about 30% longer than for a 6 foot for this reason.

I believe anybody should be happy with the keylentgh of a 6 foot baby grand, but no digital -including the Gran Touch- does reach this.

With uprights the pianodesigners have more degrees of freedom for the keylength.
Maybe we should look to the keylength of uprights that are commonly aknowledged for their action to get a reasonable measure about this.

Peter

Hmmmm... I don't see the point by mainly focusing on the keylength as a major criterium for realism of keyboard action. According to your interesting illustrations I don't see a lot difference in pressure, except for the grand. Don't forget that long keys also have some downsides, e.g. it might take longer for the keys to release back to the starting position due to a different inertia depending on mass. I think there are a lot more criteria that are even more important than a little bit more or less keylength.

Why do longer keys take longer to return? How can you be so sure?

I don't know how important or unimportant the key length is - as I said before I had never even thought about this at all. I'm glad the topic has been raised!

Greg.

I said depending on mass. And yes, it's an interesting thread, but a little one-sided.

When the mass increases the resonance frequeny goes down.
The amount of bounce back energy increases.
When the elasticity of the felts become stiffer , the frequency goes up again, but the forces needed will be higher.

Therefore keylength does not necessarily make the action slower, but increases mass inertia and forces.
That are the physical facts.

According to my piano tunining book, the better pianos have counterweights that are located between the centre rail and the capstans.

Greg.

Yes.
A counterweight thats near to the center balance does not increase mass inertia much. (This is why the weights are placed this way)

If a 5 gramm weight is placed 20 cm from center and a 10 gramm weight is placed 10 cm from the center then both have the same effect on weight. But in that case the 10 gramm weight has less effect on inertia than the 5 gramm weight ;-)
This can be calculated with some physics, but any pianotechnician can confirm it.

A little bit of key inertia might be wanted for comfort of touch, it can buffer the hammer bounce, but anything more than that is generally unwanted and fighted by piano builders.

In modern designs the weights are replaced by magnets.
Because these dont cause inertia they can be placed at the hammer where they are far more efficient because there is more leverage effect. The inertia must be located in the hammers and the pianist wants to feel the hammers inertia at the key touch surface.

Can I ask (without being punished) ; after all these pictures , measurements and explanations - do you have a short list of the keybeds that are used in DP's from best to worst ? E.g. how do PHAII, PHAIII, RM3, RH, GH3, Tp40Wood etc meassure up to your 'ideal' grand piano keybed. It think that might be very interesting for potential Dp buyers to know.

Thanks

JFP,

short answer - no.
I just want to know the technical criterias,thought a lot about it, recherched about it, experimented with it, and finally calculated the physics, got some results and want to show them.

Ok, let me rethink - most probably the Avant Grand is the best digital ;-)

Peter

Yes I agree. It's interesting stuff, a bit like a mechanical DPSD for the actions.

But it doesn't tell you how well the key action is integrated with the sound generation and response system; in other words the playability.

I wonder whether all of this demonstrates anything at all.

Can I decide whether I'll find a piano suitable based on pictures and percentage forces and key lengths? I doubt it.

The old saw still holds ... you have to try the piano before you can know how it feels.

This is exactly what it says.
The geometrical and physical parameters of all digitals are very similar and cannot be taken as a decision criteria.
The differences are minuscle compared to the differences that are between acoustics.

Exceptions are the count and placement of sensors, this is not investigated here.

The GranTouch apparently has more realistic inertia and only the Avantgrand is close to a 6 foot Baby Grand or possibly better in geometry and mass distribution.

It'd be interesting to investigate this second matter in a different thread.

Though this one has been quite interesting, I too figured that the differences wouldn't be as drastic as some people make it sound. There is a difference in how it feels, but to suggest that one keybed requires much more weight to play didn't sound right to me.

You can't deny that the pivot point location is a very fundamental element of the key action feel. As such, you can you ignore it at your peril, though perhaps this is something one unconsciously factors in when demoing keys? Still, it never hurts to know what physically or electrically corresponds to what we aesthetically approve or disapprove of.

If someone made DP keys with a pivot point more like that of a real grand, yet didn't weight a ton, I would certainly sit up and take notice.

After long research - here is it ;-)



So it is not so very much different from the GranTouch as I believed. Also the difference against the better digitals is there but it is not drastic.

This should eqal an action of a 6 foot Baby Grand.

So be happy, whatever digital you might have, play it ;-) , the action parameters are only shortly below the Avant Grand.

I'm somewhat disappointed with this discovery. I thought AG keys were the holy grail of DP feel, and now we see that they could be improved.

There's no peril in ignoring what's hidden "under the covers." A pianist only touches the parts above the covers.

By playing the piano, anyone can decide for himself if the feel is right. In contrast, you cannot make any such determination just by looking at the 200% point on the diagrams. So what's the point?

Curiosity is the point. I want to know it.

When I do something, I always want to know how it works.
When I was young I was more interested to look into the TV, than to look onto it and that has not changed ;-)

BTW, the image is taken from here: