Negative Inharmonicity

[Jim]

Hi Allen:

Yes, I've found this several times.  Unfortunately, it was always a
case of being in Mem mode when I tuned F3 to stop the dots at F5
without noticing that there were numbers in the right window
(from a mem mode tuning) then when I changed octave to 6, the dots
would travel in the flat direction.  By this time I would realize that
something was wrong, so I would hit the tune mode button, go back to
the F5 = 0.0 and retune the F3.  When I then advanced to oct. 6 the
dots would spin in the sharp direction.  The only other problem I
have encountered similar to this was when I could not get a clear
reading of the 8th partial because the hammer which strikes the
string close to the 8th partial node was blanking out the power of
the 8th partial.  Plucking the string between the strike point and
the V-bar or Agraffe solves this problem.

The Knabe Consoles which I service have F3 values ranging from
5.3 to 6.4.  The note G3 is the lowest plain steel string and it
usually has a value around 10.4.  I will usually take the measurements
as I find them and use these to compute a tuning on Page 1.  Then I
will measure the difference between the 4th & 8th partials of G3 which
will be around 10, then change the note (in tune mode) to F6 and store
that stretch number.  The other two stretch numbers will still be
available in the stretch storage area, so you can then select Page 2,
do the roll-over technique to compute a tuning which works better for
the plain strings.  I like to tune downhill from A4 using Page 2 until
I get to F#3 where I change to Page 1.  As I tune across this break,
I can flatten the G3 and G#3 a little more and sharpen the F#3, F3, and
E3 a bit to smooth out the beat rates of the 3rds.  It is good to also
listen to the 5ths across this break to insure that they don't beat
wildly.

I hope this helps a little.

Jim Coleman, Sr.



On Thu, 23 Jan 1997 Gilreath@aol.com wrote:

> Hi everybody,
>
> I ran into something interesting today and thought that I would throw it out
> to see where the discussion leads.  While tuning a Knabe console, I noticed
> that when then fourth patrial of F3 is tuned to F5 then F6 is compared you
> find that F6 if a couple of cents flat, ie. negative inharmonicity.  BTW, yes
> this is while taking the meaurements for an FAC tuning.  This note is on the
> treble bridge and has wound strings.  I remember this issue coming up a
> couple of years ago in the journal and perhaps one of you remember the
> reference and such.  Any good explanations out there for this kind of
> measurement?
>
> Thanks,
>
> Allan
>
> Allan L. Gilreath, RPT
> Gilreath Piano & Organ Co.
> Berry College
> Gilreath@aol.com
>
>