Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Kawai Regulation Manual Recommends Variable Let-off Distance

From the Kawai Upright regulation PDF:

"Let-Off should be 2.0 mm in the treble,
2.5 mm in the middle,
3.0 mm in the bass."

But most other people advise 1/8" (or 3mm) for all the notes.

It seems to make logical sense for the let-off distance to be proportional to string diameter, but too close of a let-off in the treble can make the tone too shrill.

At least that's what I have noticed....

Action regulation specs are guidelines - you don't have to strictly adhere to them if the action works better by changing them, especially by relatively small increments. If you prefer 3mm let-off in the treble, and the action works ok, by all means, use 3 mm.

Ah, I liked your original post better!

Because we all know the piano tech police are REAL!

Haha!

Ha Ha, I didn't want to be snide. You have discovered that let-off distance will cause changes in power and tone, as will blow distance changes, especially in high quality pianos. Shorten the blow or increase let-off on a Steinway grand, and the power and tone will change. That is why the regulation always needs to be good before fine voicing is done.

For me, 1/8 inch letoff is way too large in the C3-C8 range. The key repetition speed and control of pp is compromised. 1/16 inch letoff - 1/8 drop maybe, but even that is large. I have my piano set in the critical repetition range closer than 1/16. It does mean that double strikes occur if you don't always play into the key, but the control is amazing.

It does mean, however, that the regulation needs to be touched up regularly - in my case, where the piano is played 4-6 hours a day, at least once a month or more often.

OP is discussing an upright. AFAIK only Steingraeber & Sohne uprights can be set to 1/16" letoff and that is for their special double repetition model.

Ian

Yes, I'm talking about uprights.

2mm is only a tiny bit larger than 1/16", so they are practically the same, but it's too close for my Hamilton
upright. It makes the treble section tone too shrill and bright.

Plus, I don't like the idea of regulating every month or more.

Doing it once a year would be bad enough!

I would not handle with one, two or three millimeters. The question for me is: what do I need as a pianist? My answer is , that I can trust the hammers will strike the strings, if I play a cord, (e.g. C-e-g) with a slow motion through key dip. And that on all 88 keys.
Check the regulation with cords helps to improve your work.

Sorry, missed that vital piece of info. So much for my skills of observation.

Some pianos let you get away with a closer let off than others. That's why its always good to regulate some sample notes in the different sections to see what you can get away with. I like it as close as possible. The ideal is for it to be almost impossible for the note to fail even under the most delicate pianissimo.

Some pianos will get hammer stutter if the let-off is set that close, so you have to find what works.

One tip that has worked well for me is to compress the let-off buttons after setting let-off. For an upright I fully depress the key, or sometimes raise the wippen and use the let off tool to push forward on the top of the jack, forcing it into the let-off button felt. This compression will usually cause the let-off to be a little closer.

One of the issues with setting let-off is that it will tend to creep closer as the jack 's toe starts to create a new compression/wear pattern in the button. This can lead to blocking or stuttering as the regulation gets played in. Pushing the jack top while raising the wippen accelerates this and makes the let-off more stable.

At what point is too close? You can be to close for tolerance variables and have a piano that stutters every other day. Can you get too close for good sound quality or too close for good dynamics? The question I'd like answered is, "What is the optimal point of let-off in relation to where it happens in the key-stroke?"

Or: Pretty much what Bob posted earlier with key travel added to the equation.

The action cannot precisely regulated. Its hard to regulate let-off within 0.5mm tolerance. The specification probably computer generated, not strictly followed in production line.

OFF TOPIC humor:
the proper usage of Kawai regulation manual is print a hard copy and bind well. Show it to your customer:" I am former Kawai authorized technician, so I have the secret manual. I regulate your piano according to the official specification."

This is true story in Hong Kong. Once I give a soft copy to my "mentor", he demonstrated the proper use to me.