[pianotech] regulation "sweet" spot

John Delacour JD at Pianomaker.co.uk
Tue Jan 20 14:23:42 PST 2009


At 14:12 +0000 20/1/09, Steven Hopp wrote:

>...(This is my first full grand regulation).

Don't beat yourself up, then, if it's not as full as it should be.

>I am having some trouble on a few notes not finding that "sweet" 
>spot of let-off to drop ratio or point.  I am using a let-off rack 
>set to baldwin spec of 1" 7/8" and have levelled theÊhammers for a 
>proper blow distance.

As others have suggested, hammers should be bored to suit the 
individual piano; otherwise the result will never be ideal.  The 
factory bore is often wrong and it is almost always possible to get 
the piano sounding better than it ever did, especially in the high 
treble, by boring the hammers exactly -- but it's too late for that 
now and it's a long subject.

>   The majority of the notes are good and behave as expected. i.e. a 
>slow rise of hammer to a 1/16" below string strike with a 1/8" drop 
>with that little bump (what I call the sweet spot) in the feel of 
>the key as you play.  Granted on the good ones some of the "bumps" 
>are stronger than others but on some it is very weak or on the bad 
>notes it is not present at all.
>
>The questions I have are:
>
>1.  What should I do when I can not get the two Let off and drop to 
>reconcile?  (good rise vs. too much drop or poor rise with that 
>magic bump in the feel)
>
>2.  If I get the regulation button turned so low that there is no 
>more turn left and I am not getting good results what should I do 
>after starting back at beginning of that notes regulation?

The chances are, as has also been suggested, that either you have the 
drop screws too high or you have insufficient touch depth.  The 
set-off (letoff) is always adjusted before the drop, but you can't do 
the set-off unless you have previously screwed down the drop screws, 
which, in the case of a piano that has worn and been regulated, will 
always be too high.  So, roughly lower the drop screws so that you 
can regulate the set-off.

Contrary to someone else's advice, I always leave touch depth till 
last before finally regulating the drop, and I have good reasons for 
this.  If your blow is exact and your set-off good, then the desired 
touch depth will be that which brings the jack just clear of the 
roller (knuckle).  With the drop regulated fairly accurately you can 
regulate the touch depth until you get just the right kick, and this 
is best done by feel with the action in the piano.  When this is 
done, finally regulate the drop, and then recheck the kick (or 
aftertouch).  If the aftertouch is excessive -- the jack is pushed 
against the slap cushion and there is a marked kick -- then the 
regulation is inefficient, the touch is too deep.  Once the hammer 
has dropped onto the cradle the key should be bottomed so that the 
hammer can only be made to rise by pushing the key hard into the 
keybed.  Some actions will exhibit no rise of the hammer after drop, 
but with most standard Erard-Herz actions the hammer will rise very 
slightly during the aftertouch.  But the less aftertouch you have, 
consistent with clearance of the jack from the roller, the better it 
is.  There is absolutely no virtue in kick for kick's sake.

These operations all come very near the end of the process of "grand 
finishing".  Regulation begins with a whole series of far more basic 
measurements and alignments, as we all gradually learn!

JD





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