Fred Sturm, CAUT, 2/20/09 Fred, Our S&S B’s with the large chromatic offsets did show slight chromatic tuning offsets until the web screws were regularly hardened up. The B’s were more stable unison wise than the D’s. The measuring device used was a nice dial caliper and measured mostly pin to pin and where possible from an irregularity in the plate casting in the counter bearing area, not always a good measuring point but good for averages. The readings ranged from barely discernable to 0.001+ which is enough to roll the unison. On the D the chromatic offsets are much less than the unison left to right distance and I had to be cavalier in ignoring half steps. Occasionally with major weather changes over summer one of the D’s with it’s offset half steps would sound like near WT. The recital hall at HSU during my tenure was poorly controlled and also had heat production problems. During concerts and recitals humidity could rise from 30° to 60/70° measured by pocket Humidistat and once by sling psychrometer. Please recognize at 83 years I must be extra careful to try to recall accurately. I’m trying to keep the flowers out of the weeds. Also, I must in justification be very careful to use no exaggeration. I am disinclined to put my “O” through the experiment, both of us, the piano and myself being too old and tired to go there. I wish you all well, Dan Gurnee On Feb 20, 2009, at 1:02 PM, Fred Sturm wrote: > > On Feb 20, 2009, at 9:33 AM, Daniel Gurnee wrote: > >> My measurements of pin movement by block expansion/contraction >> indicated mid performance with the effect of audience moisture >> that the right pin of a unison moved farther from the capo/agraff >> than the left pin. The measurement taken by michrometer was >> assumed to be pin block expansion which may have been caused by >> humidity or temperature. > > I am intrigued by your description. How exactly did you make this > measurement? What was the magnitude? Magnitude of difference > between one pin and another? I guess there are different designs of > micrometer, but I haven't seen one that could do this. > In any case, I don't find a difference in behavior between > Steinway D and B, in spite of the difference in tuning pin array > (my earlier post, I was confused - it is B and A that have those > alternating offset groups for each unison, not D). So while it may > be that the pins move relative to termination (ie, are moved by the > expansion/contraction of the block), and that the right pin moves > more than the left, this model for the unison skew comes up against > the contradiction of alternating unisons not moving similarly - > that is, the pitch doesn't seem to move in accordance with what the > model would predict. > About hall heat and humidity, in my own experience at our venue, > with a pretty efficient HVAC (with the pluses and minuses that > presents), the only effect that seems to be significant at concert > time is lights. Ours don't put out that much radiant heat (ie, > directly radiating on the strings), and the HVAC keeps the > temperature change down to about 4 degrees rise or so on stage. RH > drops accordingly by about 1-2%. We have had several faculty who > have tried to keep RH higher in their studios using a humidifier, > and the HVAC flushes it out as fast as the humidifier produces it > (I have measured: within a few feet of the devise there is a small > effect). I don't believe the audience causes a rise in temp and RH, > or at least not a significant one (the system flushes it out as > fast as it occurs). > Older buildings without the "blessings" of modern HVAC will no > doubt have different issues, maybe including humidity rise due to > audience breathing and perspiration, as well as heat rise. And > facilities with humidity "control" may have their own special > issues where the calibration is such that they create pretty wild > seesaws (like Jeff Tanner describes). > Regards, > Fred Sturm > University of New Mexico > fssturm at unm.edu > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/caut_ptg.org/attachments/20090220/af0d0ff8/attachment.html>
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