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The problem with this is what the midi data suggests. If you are at the letoff (past the first sensor), you can still get a midi strike (or not) depending solely on how hard you press the key from that point (though still, no note sounds even if the strike is registered). That means it's impossible (super unlikely) for it to be a 2 sensor system where the first sensor is before or at the letoff.

Today I've had the fallboard off of my NV10 again (for unrelated reasons), so I thought I might try to answer this question that was still open:

We had already discussed the answer to the first question, i.e. that no, when doing this experiment, I cannot get a note played. So now I wanted to answer the second question: It is a bit difficult to tell, but from all I could see, I think the answer is yes, the hammer is indeed thrown.

So the question is, why doesn't the note play then?

My theory is, that it is a combination of the nature of the experiment itself, and the way the sensor works.

The sensor, even though it measures hammer movement optically (and not key movement by pressure, as most "normal" DPs), still measures the velocity of the hammer, not the force with which the hammer hits the stop rail.
If I understand the technology correctly, the sensor consists of a fixed optical unit (with a laser) and a shutter that is attached to the base of the hammer shank. To determine the velocity of the hammer, the sensor probably uses the shutter/laser combination to detect two positions of the hammer shank, and the velocity is then a function of the time elapsed between these two positions.

• Very short time: High velocity -> high MIDI value. This is what happens when you play ff.
• Very long time: Low velocity -> low MIDI value. This is what happens when you play pp.
• Even longer time: Velocity too low -> MIDI value 1 (=no note played). This is what happens if you botch the pp and press the key too softly.
• Much, much longer time: Velocity too low -> MIDI value 1 (=no note played). I think this is what happens in the above experiment.

As you can see, for the sound engine, there is no difference between a botched pp where the key was pressed just a tad too softly, so that no note was played, and the last case, which I think is the case that happens in the above experiment. In both cases, the system generates the MIDI value 1, which means, "key was pressed, but no note played".

Why do I think that this last case is what happens in our "experiment"? Because if you look at what happens with the hammer during the experiment, you can see that when you slowly press the key up to the resistance of the letoff, the hammer is already moved upwards quite a bit. (Which is of course totally logical. After all, the letoff is the moment when the hammer is decoupled from the key, so the hammer must already have moved at this point. If it hadn't, and the key was decoupled before the hammer even starts moving, then the hammer would never move at all!).
And since the hammer has already moved upwards quite a bit, the sensor has probably already passed the first measuring position, where the measurement for the elapsed time starts. Only we, while doing this experiment, hesitate so long until we finally press down the key fully, that it takes a (relatively) loooong time for the hammer to finally reach the second measuring position. Depending on how slowly you "feel" your way down to the letoff point and how quickly thereafter you then press down the key, the time between the two measuring positions can be even several seconds (but certainly at least some tenths of a second). And this is of course an elapsed time that never happens during normal play. So while the hammer eventually reaches the second position, the system calculates a veeeery low velocity, hence the MIDI value 1 = no note played.

So my theory is, that the way we are performing the experiment, in combination with how the sensor works, actually makes it impossible to measure what we want to measure, as we artificially increase the time between the two sensor positions so much, that the result must be "no note played".

So is that a problem when actually playing the instrument?

I don't think so. Although my technique is not good enough to reliably play "from the letoff", I assume that when a pianist who has mastered the technique does this, then he (or she) will not slowly and gently press the key down (=taking quite a bit of time) until he consciously feels the letoff, and then, after a reaction time delay (after noticing the letoff notch feeling), finally press down the key fully. That method, even if mastered, would only allow to play maybe one note every second or so. No, I think that a pianist who plays with this technique plays this much more fluidly. He has a "feeling" where the letoff is, without having to slowly approach it as we do in our experiment, so the total of the key press is still relatively quick, regarding the time between the two measuring points of the sensor, which is interpreted as a low, but not too low, velocity, which results in a low MIDI value >1, which in turn produces a pp or ppp note - just as desired.

OK, now poke holes in my theory!

Btw, just let me say I really enjoy these hypothetical musings. I imagine some engineers from Kawai and Yamaha sitting back in a chair with a hot mug of coffee, browsing through these threads and rolling their eyes thinking "psshht, amateurs!"

Regardless of the precise details on the sensors it does sound like they're set just a little too low than would be ideal in the hammer's travel.

The only picture of AvantGrand action I could find is this:


To me it seems there's only one optical shutter on the hammer shanks, in contrast to the NV10 where there are two sensors. And there are the optical sensors beneath the keys as on NU1. That makes me wonder if N-series actually measure real hammer velocity?