FAC numbers

[Richard Moody]

Hi Jim
	Hmm across the board they were off one cent give or take .2  or .3 cents.
 It looks like A4 dropped a  little.  But not enough to call for a pitch
raise....

You wrote...

> For those who are not familiar with FAC numbers used with the SATs, the
> first number represents the difference between the 4th and 8th partials
of
> the note F3. The second number represents the difference between the 2nd

> and 4th partials of A4. The third number represents the difference 
> between the 1st and 2nd partials of C6.


Jim could you explain for us "donkey cart tuners", (I hope you appreciate
that ; ) (OK  so it seems I put my foot in it ) why F3, A4, and C6 were
chosen for the FAC, and why the difference between such a wide range of
partials beginning with the 4th and 8th partials of F3?  
>From theory F to C is a fifth which is sounds 3 partial to 2 partial. How
come a third partial isn't measured?  

Actually you don't have to explain as from what I have heard of the FAC
formulation, these machines seems as accurate as the ear, and I am sure
there are demonstrations that prove that either is superior, or both are
better. 
	As an aural tuner, I am wondering how you feel about the choice for
partials that are measured in the FAC. 

Richard Moody 

ps You wrote

> When I came back today to do the fine tuning, they were:   14.5, 8.0,
5.7.
> The change is not due to the strings getting longer, but shorter if 
> anything. The diameters did not change. The bends at the terminations 
> may have changed slightly. I still think that it has something to do
with
> the soundboard loading.

My guess is,  if the soundboard presses up on the strings a little more
they go sharp.  If the crown dips a miniscule, the pitch drop it seems can
be detected by machine... If the cabinet door sticks in wet weather, I
wonder what the sb does. 

Richard Moody 



----------
> From: Jim Coleman, Sr. <pianotoo@imap2.asu.edu>
> To: Richard Moody <remoody@easnet.net>
> Cc: pianotech@ptg.org
> Subject: Re: Inharmonicity
> Date: Friday, August 21, 1998 5:03 PM
> 
> Hi Richard:
> 
> When a partial is flatter than its theoretical harmonic, we know that 
> something unusual is going on. Dean Reyburn invented the word 
> para-inharmonicity to cover a multitude of these kind of sins. I suspect

> that it has something to do with soundboard movement.
> 
> Perhaps related to that is something I documented today on a
pitch-raising
> job. The FAC numbers I measured before pitch raising were: 15.3, 9.0,
7.0.
> When I came back today to do the fine tuning, they were:   14.5, 8.0,
5.7.
> The change is not due to the strings getting longer, but shorter if 
> anything. The diameters did not change. The bends at the terminations 
> may have changed slightly. I still think that it has something to do
with
> the soundboard loading.
> 
> For those who are not familiar with FAC numbers used with the SATs, the
> first number represents the difference between the 4th and 8th partials
of
> the note F3. The second number represents the difference between the 2nd

> and 4th partials of A4. The third number represents the difference 
> between the 1st and 2nd partials of C6.
> 
> Jim Coleman, Sr.
> 
> PS the amount of flatness observed for the second partial on some pianos
> has usually been on the order of .5 cents. For pianos with the 1 inch
over-
> wrap at the bridge ends, it has been more extensive and it has affected 
> more than just the second partials. I have also seen a few cases where
the
> 3rd partial was flatter than the 2nd partial. Usually everything smooths
out
> by the time you get the 4th and 5th partials. This is my primary reason
for
> not tuning by 3rd partials in the tenor area.  JWC
> 
> On Fri, 21 Aug 1998, Richard Moody wrote:
> 
> > Hi Jim 
> > 
> > >>There are two
> >  7' pianos in which the second partial of C5 is flatter than the
> > fundamental.<<
> > 
> > 	The second partial of C5 is FLATTER that the fundamental?  You mean
it is
> > flatter from 2x the fundmental.??
> > What pray tell could cause that?  It seems that in piano wire with
> > stiffness being a factor of ih, all partials MUST be sharp.  
> > How much flatter? 
> > 
> > Richard Moody 
> > 
> > ----------
> > > From: Jim Coleman, Sr. <pianotoo@imap2.asu.edu>
> > > To: Richard Moody <remoody@easnet.net>
> > > Cc: pianotech@ptg.org
> > > Subject: Re: Inharmonicity
> > > Date: Thursday, August 20, 1998 12:52 AM
> > > 
> > > Hi Richard:
> > > 
> > > The variations of inharmonicity especially in the lower numbered
> > partials
> > > is something which can be seen even in plain wire strings. There are
two
> > > 7' pianos in which the second partial of C5 is flatter than the
> > fundamental.
> > > This is most unusual.
> > > 
> > > More variation is observed in wound strings in general. The most
weird
> > thing
> > > is found when the copper wrap is over wrapped for about one inch at
the
> > > bridge end of the strings. This often causes more than just the
second 
> > > partial to be flatter than the fundamental and makes tuning by any
means
> > > utterly impossible. This phenomenon was witnessed on one of the most
> > > prestigious 6' piano in the world.
> > > 
> > > Jim Coleman, Sr.
> >