Spring fever (or feverish springs)

[A440A]

Ed T writes:
<< You can weaken the rep
springs to where at a soft blow as you described it would feel better to you
but the trade off is in fast repetition.  This is the side I want to fudge to.
I believe, as Yamaha, to set those reps with a fast rise..>>

      Hmmm,   has anyone found that rep springs give faster repetition when
they jump hard enough to be felt in the key, as opposed to those springs that
are set only as fast as possible to not be felt? 
     I ask this because repetition speed has not, in my experience, been
compromised by the softer setting.  It helps to remember that the spring does
not lift the hammer during fast repetition.  It lifts the KEY!!  
      You may demonstrate this by striking a note, and with the hammer held in
check,slide you finger off the front of the key, allowing the fastest possible
resetting of the jack.  You will see that the hammer does not rise one bit,
but rather, stays in place until the key has risen enough to allow the whippen
to drop, which the shank then follows.  If you have doubts, go to your action
model and place a finger directly over the hammer and check, then let go of
the key.  The hammer will not rise before it drops.  We set the springs by
observing their rise rate, but in fast repetition, the hammer begins each
repeated note from its checking distance. 
    The spring speeds repetition by more quickly overcoming the inertia of the
key;  it does this by pushing off against the leveraged weight of the hammer.
The difference in key return speed between a spring that "kicks" and one that
isn't felt is minimal.  
   Of far greater importance to repetition speed is the height of the
checking.  It determines how far the key must rise before the jack is reset.
It is also important to know that the softer the spring, the more consistant
everything in the action must be to perform, i.e.  erratic pinning will
require the springs to be set stronger, just for a margin of safety.  
   When Alicia de la Roccha played here, she stood up from the Steinway D, (
with my "soft" springs in it, and said " This is the first piano I have ever
played that I don't need to have the technician speed up,  just tune it, but
don't touch that action!".  
    Also,  with the softer settings, the drop can be set at let-off distance,
further increasing the sensitivity of the action at pianissimo levels of play.
This is important when you have the let-off set to just barely miss the
excursion limits of the string.  
   Perhaps for the average-use instrument, strong springs allow fewer service
calls , but for ultimate performance, they get in the way.  

(Hot Damn!!  Flame suit fresh from the oven, pulled on and zipped up
tight!!!!!!)

Regards to all, 
Ed Foote