Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum FAQ - Tuner-Technicians Forum What is the technical name for this problem?

I just recently purchased a used Kawai that is about 40 years old. I had a technician check it out first, and he said it just needed tuning, and minor pedal repairs. So I had that done, and while the tone does sound pretty good, it does this really annoying thing occasionally and inconsistently. Sometimes when I strike a key (random keys, although one in particular), it does a double bounce off the string, so it sounds...I don't know how to describe it, the word warbled comes to mind. I assume there is a proper name to describe this phenomenon. What causes it, and how is it fixed? Is it something to do with the felt? I had it tuned shortly after it arrived at my house, and I assumed this would be fixed as part of the tuning process.

You might want to re-post this in the Tuner-Technicians Forum -- the regular forum, not the "frequently asked questions" section. You will get more answers and suggestions posting there.

It is most likely to be 'hammer bubbling'...the hammer plays twice of some sort when the key is struck?

It is most likely to be 'hammer bubbling'...the hammer plays twice of
some sort when the key is struck?

This is called double striking. This is caused when the backcheck does not catch the hammer at the end of the action cycle. This can be fixed by carefully bending the backcheck forward. The hammer should catch on the backcheck 1/2" to 5/8" from the string. I would have your local piano technician take care of this simple fix. Is your Kawai an upright or a grand?

Nick

I call it double striking or double bouncing. It can be fixed by bending the back check, but the problem with that is you may make the back check "catch" the hammer as it rises to the string. Regulation is a much better choice when dealing with a double bounce.



Jay
Jays Piano Tuning Service
www.jays-piano-tuning.com

It's also called "hammer bobbling" or (in the UK in times past) "blubbering". Double-striking is the best technical term for it.

Beside the back-check not catching it can also be that jack is not clearing the but of the hammer - thus the hammer is bounced back. Also the tape, which pulls the hammer, back may be slack.
I take it that it is an upright piano ?
If you are going to try on your own to fix the problem - look for videos on YouTube there are at least two showing on models how to do things.

The tape does not pull the hammer back.
Ian

Greetings,
"Tuning' is the alteration of the pitch of the strings. It is not a mechanical repair of your action. It may be that the regulation is gone, and there is insufficient key-dip for the action to complete the full cycle of escapemtent.

This is a regulation problem, and I would caution not to start bending wires until you know you have sufficient after-touch.
Regards,