Front Duplex

[Kevin E. Ramsey]

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Re: Front DuplexRon,=20
    Thanks for the straight info. I only mentioned the SD-10 as perhaps =
being a little different because of the steel insert capos. They are =
really different.=20
    I forgot all about Jim Coleman's glue trick. He told me about it and =
I guess I filed it in the wrong memory module. I remember saying "That's =
neat, I can't wait to try it." I'm so embarrassed.
    Anyway, a lot of good info here, Thanks.



  ----- Original Message -----=20
  From: Overs Pianos=20

  Susan's article was about an SD-10, but front duplex problems are the =
same regardless of the manufacturer. There are pretty new pianos out =
there which don't sound too pretty, with noises aplenty.


  Duplex bars which are:
  * larger radius
  * softer than the wire
  * close to in-tune with a harmonic of the speaking length
  * too long
  are all factors which contribute to string noise.


  Ideally the front duplex should be:
  * a small radius (these days we are setting to 1mm or slightly less)
  * harder than the wire (when rebuilding we harden the cast in bar)
  * shorter, 40 mm is too long, under 30 is preferable though often =
impossible to achieve.
  * set to a detuned length, ie. to a length mid way between two =
harmonic lengths
  * set to a height for a string approach angle of not greater than 15 =
degrees (or the wire will be cut by the non-deforming small-radius =
duplex bar).


  The 'glue on the duplex length' trick (thank you Jim Coleman snr), to =
increase mass and therefore to detune, is a very effective on the road =
fix.


  We nickel plate our front duplex bars (after hardening) to improve =
string rendering and to prevent corrosion.


  Ron O.
  --=20

         OVERS PIANOS
  Grand piano manufacturers
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