Robert Conrad, Registered Piano Tuner/Technician, Tucson, AZ

FAC Tweaks: Which one should I do first?

This post suggests a general approach to applying these FAC Tweaks.

The A Multiplier Default:
I’d suggest leaving the A Multiplier Default @ 1.0.

The A Multiplier Def tweak was originally a way to put an FAC Tuning’s A4 closer to A440.
Setting the A Multiplier Def to .8 will accomplish that task.

However, now that the AccuTuner has the Partial Change Correction (PCC) feature as part of it’s software, PCC can be used to correct any error at A4.

Now the A Multiplier Default can be used to contract or expand the width of the A2-A4 double octave.  The ‘range’ of the A Multiplier Default is actually quite large – from .1 – 2.0.  That means the A Multiplier Default can be used to not only contract the width of the A2-A4 double octave, but can also be used to expand the A2/A4 double octave as well.

So, if you are continually wanting more or less stretch in the midrange of an FAC tuning, you can set the A Multiplier Default  to your preferred setting, while remaining confident A4 will remain at A440.

The location of A4 can easily be corrected as part of the PCC feature.

First, Tune A4 to A440 and measure the location of A4’s 4th Partial.
(Tune A4 to A440  (A4 @ 0.0) and then set the SAT to A6 and measure the location of A4’s 4th Partial when A4 is tuned to A440.)

Do that before measuring any FAC numbers!   This will tell you the exact setting you want for A4 on the FAC tuning.  Write that number down, or remember it.   (You’ll need it later to correct the location of A4 after using the PCC feature in the upper half of the piano.)

Now measure the FAC numbers as usual and store the tuning to a page of memory.

In order to have a complete Two-Octave A2-A4 temperament/midrange for  aural checking, lower the tenor partial change down from B2/C3 to G#2/A2.

Lowering the tenor partial change.

Now that the tenor partial change has been lowered, use the Partial Change Correction feature to check and/or correct the partial changes found in the FAC tuning.   

As part of the PCC, A4 will be corrected so it is exactly A440.

Start at the top with the Treble (B5/C6) partial change, and then do the Midrange (B4/C5) partial change.

Once both of those are corrected, use the C8 tweak, which is part of the PCC feature to correct the location of A4.

After A4 has been corrected, correct the Tenor partial change which is now located between G#2/A2.

You can find complete instructions and videos here:  The Partial Change Correction Feature

The FAC tuning is now ready to use.

Now that all the partial changes have been corrected, you will hear no hiccups in the tuning related to an error at a partial change.

Going the extra mile.  Taking your tunings up a notch!!

Now that there is a complete two-octave A2-A4 midrange with no partial changes,  if you want, you can tune some selective notes within that A2-A4 two octave range so you can check to see if you might want to contract or expand the A2-A4 double octave.

Tune tune some selective 3rds, or 4ths and 5ths, and A2, A3 and A4.
{Once you decide which notes you want to tune regularly to make these checks, you may want to create a tuning sequence of just those notes.  Using a tuning sequence can be a handy time saver.  You can see how to create a sequence here:  Using a Sequence

I’m now going to talk a little about the location of A2.

After doing all these FAC tweaks, a quick look at the setting of A2 can tell you a lot.

Here’s some guidance from Al Sanderson:   You can find this is Appendix E of the SAT instruction manual, where he says that if A2 starts to get much below -4.0, the double octave may be too wide:

“Step 2. Tune A2 from A3 as a 3-6 octave 1 cent wide. Check the A2-A4 double octave, and if it is more than 4 cents wide, divide the excess by three and narrow both octaves by this amount. (E.g., if double octave is 5.5 cents wide, 5.5-4 is 1.5, divide by 3, and narrow both octaves .5 cent.)”

The subject of ‘the width of the A2/A4 double octave’ is too big a subject for this particular post on which of these FAC tweaks to do first.

So let me condense some of my observations and experiences to give you some basic guidelines for you to used regarding the location of A2.

As Al says, when A2 starts to get down to a setting of -4, it’s time to do some checking.   The A2/A4 double octave may be too wide (beating too fast).   You might want or need to contract the double octave to reduce some of the beating.

Double Octave Beat (DOB) can be used and to contract the tuning.   DOB is a very useful feature of the AccuTuner, and can be used in a number of different ways to either contract or expand the stretch of the memory tuning – FAC or otherwise.   DOB can be used on any tuning in the SAT’s memory

You can read up on in in your instruction manual, but for purposes here, all I’ll say is that each .1 DOB will move A2 by .4 c.  A4 is not affected.   A4 is left unchanged.

A (+) DOB will expand the stretch of the tuning, and a (-) DOB contracts the stretch of the tuning

So if after lowering the tenor partial change, and after using the PCC to correct the midrange and treble partial changes, and after using the C8 tweak to correct the location of A4, if you are now looking at an A4 setting of -4.0 or lower, you might want to use a little DOB to contract the midrange.   Any DOB adjustments will not effect the PCC corrections!  They will still be fine and correct.

As I said,  each .1 DOB will effect A2 by .4 c.   So if your A2 is -4.2, a setting of -.1 DOB will contract the stretch of the tuning and raise A2 by .4 c., resulting in an A2 setting of -3.8.   If you think the A2/A4 double octave is still too noisy, try using -.2 DOB.   The -.2 DOB will raise A2 another .4 c. and give you an A2 setting of -3.4 c.

Again, A4 is not effected by DOB.   A4 will remain the same.  And so will all the corrections you made with PCC. and your correction of A4.

What you’re doing is using Double Octave Beat (DOB) to simply remove some of the stretch from the midrange/temperament area.

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A tip for using the A Multiplier Default:

If you start using these tweaks on a regular basis, and consistently find yourself needing to use some DOB to contract the A2/A4 double octave, you might now consider using the A Multiplier Default to contract this a little from the get go.   You can set the A Multiplier in the SAT MENU to anywhere from -.4 to 2.0.  The default is 1.0.

For starters thought, I’d suggest leaving the A multiplier default set to 1.0.   Do the above tweaks for a while on a number of pianos, a number of spinets, a number of consoles, a number of grands, small, medium and large.

If you are consistently getting an A2 lower than -4.0, using a A Multiplier Default of .9 or .8 might contract the A2/A4 double octave just enough for a better sounding midrange area.

After a while, your experience will guide you into the most efficient application of these tweaks.

You might find yourself using a certain A multiplier for the smaller pianos, or for verticals, and another one fairly consistently for smaller grands vs. larger grands.

Be patient.  Keep listening and paying attention to some of the settings your getting for A2.   I know you will soon start hearing an improvement in your tunings.

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More guidelines regarding the location of A2: 

As I said, the subject of the location of A2 is one I could talk about for a long time.   I referenced Al Sanderson’s guideline first.

Here’s something you can and should do on your own:
Tune A4 to A44o, and then tune A2 as a 4:1 1 c. wide,.
then 1.5 c. wide
then 2.0 c. wide
then 2.5 c. wide
then 3.0 c. wide
then 3.5 c. wide
then 4.0 c. wide
then 4.5, c. wide
then 5.0 c. wide
and then 6 c. wide.

Somewhere along the line, you will hear a place – a width – when you will think the double octave sounds too wide.

Once you do, you will have put a number to a beat rate which may be your own guideline ‘tolerance’ of your own.   A number you can use, your own reference, as to what might be getting too wide.

If your reference is 3, or 3.5, or 4 you can use that along with Al’s 4.0 width.

A bit of my own empirical data:

I just averaged the A2 settings for 261 tunings in my database.  The average A2 setting was -2.6 c.  (a 2.6 c. wide, A2/A4, 4:1, double octave.

However, within that group of 300 tunings I had a -6.5, a -6.1 a -5.9, a -5.8 a -5.1 a pair of -4.7’s and so on.

Yes, a -6.5, and yes, a -5.8!  There were times when I just had to have a exceptionally low A2.  On those pianos it was part of the best compromise I could make.

There are exceptions, and there are times when even Al’s -4.0 width needs to be breached.   Thank goodness the exceptions are rare.   But they’re out there.  My hope is that when you come across one, you will have been doing this long enough, so you will know how to deal with them.   The AccuTuner has some built in tools that can help you deal with them to a great extent, but you have to not only recognize the exceptions when you come across one, but you must also know how to deal with them so that you can find a decent sound compromise for those really challenging scales.

On the other end of the spectrum, my database contains a few -1.5’s and a number of pianos with A2’s less than -2.0.

This is all perfectly and wonderfully piano dependent, of course.   But it’s up to us to try to find the sweetest spot we can for each instrument.

I’m confident, if you do these routines, in this order, you will hear a difference in your work on a consistent basis.

Yes, these tweaks may take you a few minutes, but I expect your results will be worth the time and effort.

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