Pure Sound (was A 435 or A 440 ?)

[Stéphane Collin]

Hello Ed.

I can not claim that I have a long time experience using Pure Sound wire.  But I did some tests when I was about to restring a 1864 Pleyel piano.

Pure Sound is a bit heavier wire than Röslau : it's volumetric mass is 7900 kg/m³, while Röslau's is 7850 Kg/m³.
This means that if you use the same speaking lengths and the same diameters, you will need a bit more tension with Pure Sound to achieve the same frequency.  Well, not much difference at this level between the two materials.
More significant difference is in the elasticity modulus (Young's modulus), which tells about how easily the material bends or stretches.  This is 187.5 kN/mm² for Pure Sound, while 210 kN/mm² for Röslau (those numbers represent the stress in kN to apply theoretically to a 1mm² section wire in order to double it's length).  So, while slightly heavier material, Pure Sound is more flexible.
Another difference of practical use when stringing is the breaking strength.  In my example of a A4 wire of 0.85 mm diameter, Pure Sound would break at 113.8 kg force while Röslau at 137 kg force.  So, Pure Sound breaks earlier when tension rises, or, for a same speaking length and same diameter string at same pitch, will be closer to breaking strength than Röslau.

My tests were intended to make the link with the practical world of piano shop and the subjective appreciation of the sound given in situation by those different strings.  I limited myself to installing side by side a Röslau string and a Pure Sound string on the same unisson at 3 different octaves with appropriate and similar gauge, and explore the sound quality of single note, octave and double octave when progressively rising the tension.
So I first tuned the strings at their "normal" pitch, that is at the frequency of the note as compared to A4 = 440 Hz, and waited for a week or so, doing many tunings until the strings were a bit stabilized.  First remark : Pure Sound was much quicker stable than Röslau.
When compared at that normal pitch, the intuitive feeling is that Pure Sound has less subjective inharmonicity, I mean that a single note sounds indeed more pure than the same note with Röslau, more calm sound if you see what I mean.  This is due, I think, to the smaller elasticity modulus, allowing the wire to bend easier at the termination points.  Now, when playing octaves, the good feeling of low inharmonicity seems to be decieving, turning into a lack of character.  Also (but not really sure of that) I had a feeling of less power with Pure Sound.  Difficult to say with one string.
Then I started tweeking the tensions to simulate what if I would rescale with other tensions.
Röslau wire broke in the piano at an augmented fourth above it's normal pitch (compared to A4 = 440 Hz), and Pure Sound broke at only a major third above it's normal pitch.
Röslau sounds awful when tensionned less than a major second below it's intended pitch, sounds great when at pitch, and looses much interest and sustain when pulled over pitch.  C4 lasting 18 seconds (approximately, from what I could hear) reduces it's sustain to only 9 seconds when pulled up to the pitch of F#4.
Pure Sound, indeed, still sounds acceptable even a major third under it's normal pitch, but has the same tendency to loose interest at higher tensions.

What I for now retain of my experiment (before other experiments confirm or infirm this, of course), is that Pure Sound accepts (as claimed by Juan màs Cabré) to be lower tensionned than equivalent Röslau gauge (and probably gaining so a bit inharmonicity, which I believe is necessary for a good piano sound).  I see no valid point in trying to string as close as possible to the material breaking strength (as claimed long ago by Mersenne, but he was talking violin and cat guts) as in my opinion the sound gets progressively less interesting and certainly less long lasting in that area (not talking about the thump sound that gets really ennoying).  So I would tend to choose Pure Sound for older shorter scales indeed, in a low tension figure.
Anyway, I feel that when choosing Pure Sound wire a rescaling would be needed, if possible by ear.  Retaining the original scaling gauges for the sake of respecting the original makes no sense to me in this case.

Of course, one can only juge on a whole stringing job that has streched for many month, in order to give a pertinent aesthetic value to the result.  Then, restring the same piano with other scaling and/or other material, see if it improves the whole figure.

I hope others with experience with Pure Sound will chime in and share their founds.

P.s. : I ended up stringing the 1864 Pleyel with Röslau, because the Röslau wire sounded great when matching the scaling gauges that were there (possibly not original, though).  I believe Pleyel has been very quick to import, copy and improve English steel, and the model I was working on was evidently a straight forward one.

p.s. 2 : long ago, I restringed a 1895 Bechstein model D (240 cm) with Pure Sound, retaining original gauges.  The piano lacked interest and charm, for sure, but was this due to stringing or to something else ?  Dunno.  Anyway, I'm sure now that for Bechstein pianos, from the start (1853), Röslau is a better choice, better matching the original material.

Best regards.

Stéphane Collin.





  ----- Original Message ----- 
  From: ed440 at mindspring.com 
  To: Pianotech List 
  Sent: Wednesday, July 26, 2006 2:54 PM
  Subject: Pure Sound (was A 435 or A 440 ?)


  Stephane-
  Would you tell us your impressions of Pure Sound wire?
  Ed Sutton


-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/pianotech.php/attachments/20060726/8544f468/attachment.html