SAT II

[Jim Coleman, Sr.]

Hi Rogerio:

Since no one else has responded today, I'll take it on. If you try averaging
the Stretch numbers, you defeat the purpose of having 3 stretch numbers. The
F3 stretch lets the machine know how much to stretch the lower Tenor section
primarily. The A4 Stretch No. controls the entire piano stretch from A0 
to C8. The C6 Stretch number controls the top octave primarily with some
affect upon octave 6.

Please read my articles in the Jun, Jul issues of the Piano Technician 
Journal for 1997. In these articles I show how to vary the numbers if you
have personal preferences that are different from the way FAC normally
controls the double octave widths (hence single octaves too). It is my
opinion that averaging the FAC numbers can get you into trouble. There is
a better approach. Read my articles in the appendix of the SAT Manual. You
can also find the Manual on the internet at:

http://www.concentric.net/~Fast440/atm/atm.html

It is not true that the FAC program truncates any number above 12. It does
however truncate any numbers for F3 which are above 20.

Increasing the F3 number will cause you to tune the Tenor and especially 
the Bass flatter than normal. Increasing the C6 number will force the hi
treble to be sharper if you like. conversely, decreasing those numbers will
draw in the extremes of the piano. Often I would increase the F3 number
to stretch out the Tenor and then recalculate with a smaller number while
tuning the wound strings. With the new SAT III, I can do this on the fly by 
using the Double Octave Beat control.

If you decrease the F3 number (which is used to compute the inharmonicity
constant for that note) it will cause the Tenor octaves to be too tight or
narrow. If the note you measure the F3 is a wound string, the F3-F4 octave
will sound good, but the lowest plain steel strings will be too sharp. and,
there will still be a bad jump at the break between plain wire and the wound
strings on most small pianos. In my opinion, averaging the three FAC numbers
may have some advantage in raising the pitch of the high treble, but there
are better ways of doing that.

Jim Coleman, Sr.

On Fri, 19 Mar 1999, Rogerio Cunha wrote:

> Hello list.
> I read some articles about stretch numbers used on SAT II but there was =
> on them very much information and this now is very confused to me.
> I need practically now what happens if I increase or decrease the =
> stretch to the F, the same to the A and the same to the C.
> I need this because in some bad pianos, normally those that have stretch =
> numbers with great discrepancy between them, I use to find the average =
> of the 3 stretch numbers, use this average to the A and the average =
> minus 1 cent to the stretch of the F and the average more 1 cent to the =
> C.
> The result is better than if I were using the really stretch numbers but =
> I think that would  be better to work with this numbers knowing the =
> final result.
> One thing more: is correct that if the stretch to F is greater than 12, =
> the SAT II use only the number 12 ?
> I thanks to all
> ROGERIO CUNHA - IC MEMBER OF THE GUILD
> 
> 
>