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longitudinal mode vibrations in a Kawai k2

  • 1.  longitudinal mode vibrations in a Kawai k2

    Posted 13 days ago
    Hi everyone,
    I'm trying to solve an issue with a Kawai k2 upright, about 5-6 years old. I'd like to know if this is a common issue in this model, and what to do about it. There is a high-pitched, annoying vibration in the last single wound bass string B1, and a similar one on the right string of C. The Kawai rep suggested that it is a longitudinal mode vibration and is not likely to be solved by replacement, although he thought a custom string from Arledge of a different design might help. Here's the list of possibilities I have told the customer:
    1. live with the noise
    2. let me return and give the string a twist
    3. Try a duplicate replacement (Mapes has the scale info)
    4. Try a different design from Arledge.

    Anything else I'm missing? I was not able to find any other reason for the noise. Can this develop over time, and could other strings start to exhibit the same issues?

    thanks,
    Scott

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    Scott Cole, RPT
    rvpianotuner.com
    Talent, OR
    (541-601-9033
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  • 2.  RE: longitudinal mode vibrations in a Kawai k2

    Posted 13 days ago
    Might it be a loose winding on the string?

    Best wishes

    David P

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    David Pinnegar, B.Sc., A.R.C.S.
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    +44 1342 850594





  • 3.  RE: longitudinal mode vibrations in a Kawai k2

    Posted 13 days ago
    James Arledge has a great video on longitudinal waves in, specifically, wound bass strings.

    http://www.pianostrings.com/LONGITUDINAL.htm

    I have run into this perhaps twice. One customer chose to learn to ignore the problem. The other chose to get rid of the piano and get a digital. In both cases I had tried twisting the string as well as tapping down the winding to make sure it was tight to no avail. According to Arledge, I think the best solution in both of these pianos would have been to redesign the string so that standing wave no longer existed at that frequency. I never got the chance.

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    Geoff Sykes, RPT
    Los Angeles CA
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  • 4.  RE: longitudinal mode vibrations in a Kawai k2

    Posted 12 days ago
    For the C, you might try a PitchLock coupler. That may mitigate it enough to satisfy. Unfortunately the B ...

    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 5.  RE: longitudinal mode vibrations in a Kawai k2

    Posted 12 days ago
    Geoff,
    Great video, thanks!
    For anyone who hasn't watched it, the crucial test for determining whether a string of a different tension will improve things happens at about 12 minutes in.
    Scott

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    Scott Cole, Registered Piano Technician and Doctor of Music
    Serving Southern Oregon and Northern California
    (541)601-9033







  • 6.  RE: longitudinal mode vibrations in a Kawai k2

    Posted 12 days ago
    What!? A Steinway with vertical hitch pins and a bass cut-off bar!

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    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com
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