Measuring FAC (was Re: [CAUT] Re. Link to Young Paper)Yes David I will but I must leave for 2 days in New York City so will reply in detail on Thursday. Sorry for disconnect.
Chris
----- Original Message -----
From: David Ilvedson
To: caut at ptg.org
Sent: Monday, January 22, 2007 10:30 PM
Subject: Re: [CAUT] Measuring FAC (was Re: Re. Link to Young Paper)
So Chris, where do you start your tuning? 1st tenor string going up? Temperment sequence? Could you give an example of your DOB use?
David Ilvedson, RPT
Pacifica, CA 94044
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Original message
From: "Chris Solliday"
To: "College and University Technicians"
Received: 1/22/2007 4:32:18 PM
Subject: Re: [CAUT] Measuring FAC (was Re: Re. Link to Young Paper)
Personally I stick to the Accu-Tuner III using Fred procedure for the A factor and then store the tuning on a page in memory using the defaults 8.0 for F and 6.0 for C. Everything else I calculate on the fly with the DOB Calculator,e.g., I no longer need many pages in memory as each tuning is custom and accurate. This is the most felxible use of the Accu-Tuner III and since the battery almost never runs out why would anyone use anything else? As part of my habit I also check unisons by ear to the 3rd partial. This gives me as good a tuning as I can get aurally and is replicatible to boot.
BTW forget parainharmonicity since it doesn't exist.
----- Original Message -----
From: Porritt, David
To: College and University Technicians
Sent: Monday, January 22, 2007 6:31 PM
Subject: Re: [CAUT] Measuring FAC (was Re: Re. Link to Young Paper)
Fred:
I no longer have an SAT. I've found TuneLab to be easier to measure as it's semi-automatic. It needs 4 notes I use 6. It does a good job. Still, I tune from F3 - C8 checking things along the way. When I tune from E3 - A0 I turn off TuneLab when I get to the wrapped strings. I'm much more interested in smooth octaves than compliance to a particular octave size (6:3, 8:4 whatever) or smooth progression of beat rates. It also helps battery life!
dave
David M. Porritt
dporritt at smu.edu
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From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Fred Sturm
Sent: Monday, January 22, 2007 4:55 PM
To: caut
Subject: [CAUT] Measuring FAC (was Re: Re. Link to Young Paper)
On 1/19/07 8:30 PM, "Jim Busby" <jim_busby at byu.edu> wrote:
Hi Fred,
At a convention someone mentioned this as "the" way one should take the FAC measurements. Wasn't this in the journal once too? I'm still unclear as to the "step by step" instructions. (1, 2, 3.) For the gadget impaired, (me) would you give those instructions???
Thanks,
Jim Busby
Hi Jim,
I am not aware of anyone teaching this particular method. I have heard of a couple of different variants, at least one of which was published in the Journal, but they were substantially different and for different purposes.
Here are step by step instructions:
1) Turn on SAT, press tune button. You are at A4, 0.0 cents. Tune the string and stop the lights. (Side effect: WOW! You have tuned a string to the pitch where you want to leave it).
2) Octave up to A6. Play A4 holding the measure button to stop the lights (or do cents up, whichever you prefer, and whichever produces more accuracy - maybe a combination).
3) Take that number and multiply it by 0.8. (Eg, 10.0 x 0.8 = 8.0). Using the cents down button, move the display number to the resulting number (Eg, from 10.0 to 8.0). Enter that number (Shift/Stretch) and the display will now move to C6, 0.0 cents.
(For ease in doing this in my head, I prefer to think of it as reducing the number by 1/5. Divide the number by 5 and subtract that from the total. And, hoping not to confuse the issue, an additional mathematical trick to accomplish this is to multiply by 2 and then divide by 10. So, eg, 11.7 x 2 = 23.4 / 10 = 2.3. 11.7 - 2.3 = 9.4. If this seems like gibberish, ignore it. If it makes sense, use it.).
4) Now you are on C6 at 0.0. Tune C6 to stop the lights.
5) Octave up to C8. Measure. I find it helpful to do cents up with the cents up button to about 30 cents, then use the measure button (makes it easier for the SAT to find the pitch).
6) Take this result and divide it by 5. (Eg, 35.0 / 5 = 7.0). Octave down to C7. Cents down to the resulting number. Enter that number (shift/stretch). The display moves to F5, 0.0 cents.
7) Do F as usual.
But I'll comment a little on the F number, which, it seems to me, is the weakest link in the FAC system. I find that it doesn't really serve well for pianos that have high inharmonicity for F3. The major effect of a high F number is seen in the bass, from A0 to B2, and high F numbers will produce octaves that are too wide (IMO), especially for those spinets to studios which have the highest numbers.
And, of course, it all depends whether F3 is wound or plain wire. The scaling of a Hamilton is very close to that of an Acrosonic, except the Hamilton has a plain F3 while Acrosonic has a wound F3. So the Acrosonic's F number is a lot lower. There are lots of other similar examples.
Bottom line, I reduce high F numbers, usually to a nominal 10.0
8) "Across the break." As long as I've gone into this much detail, I'll mention a bit about tuning across the break, meaning in pianos with a big jump in inharmonicity between plain and wound strings. Sanderson provides an article or two (or they did ten years ago) suggesting the use of two tuning pages to smooth the tuning across the break. One tuning uses the measured F number, the other uses a lower number derived by measuring the top wound string, as I recall. The instructions are to use the page with the higher F number for the plain wires, the lower number for the wound strings. This does make for better octaves in the tenor and bass (as I described above, in advocating for a lower F number), but it does nothing to smooth the transition across the break, defined as making the M3, M6, M10 beat rates progress more evenly. In fact, the two tuning pages will have numbers that are identical in the area across the break (or, at most, varying by 0.1 to 0.2 cents, basically insignificant).
Bottom line, I'd advise not bothering. If you want to smooth the break, I can give you a way to do it with a SAT. I'm not convinced anyone but a tuner would notice. People notice the break, but not because the M3s don't progress or have a little jog in beat rate. It's because the inharmonicity changes, so the sound of the notes themselves, and especially the sound of octaves and 5ths changes. And there is nothing we can do about it in tuning the piano. The partial ladders line up differently, and they are going to no matter what. Better to "let the numbers fall where they may" and focus instead on unisons in that area, IMO.
I hope this is helpful.
Regards,
Fred Sturm
University of New Mexico
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From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Fred Sturm
Sent: Friday, January 19, 2007 4:47 PM
To: caut
Subject: Re: [CAUT] Re. Link to Young Paper
On 1/19/07 3:29 PM, "David Brown" <David.C.Brown.2 at asu.edu> wrote:
Dear Fred-
I wonder if you could expand on this a bit more. I attempted to calculate FAC this way after reading your post but I must have done something wrong. The difference between the first and fourth partial of A4 seemed to yield a wider octave ( larger A number, to be expected I suppose) than the normal reading, but the difference between the first and fourth partial of C 6 yielded numbers well into the 20's or 30's! I tried the the difference between the first and second partial of C7 as well and still no real usable numbers for me. There must be a way to enlighten me!
Hope all is well in New Mexico.
Regards-
David
Hi David,
The A4/A6 difference needs to be multiplied by 0.8, to factor out the difference between 1st and 2nd partial and leave the difference between 2nd and 4th partial. The C6/C8 difference needs to be multiplied by 0.2 to factor out the difference between 2nd and 4th partial and leave the difference between 1st and 2nd partial. The difference between 1st and second partial is 1/4 the difference between 2nd and 4th partial (it's a logarithmic scale, based on a square of the difference between partial numbers, kind of).
So, if you read A4/A6 as 10 (zero A4 and read its 4th partial at A6 as plus 10 cents), you enter 8 as the A number. When you have calculated the tuning, the number for A4 (the tuning offset, tuning it's 4th partial) will be 10. For C6/C8, if the number is 35 (C6 zeroed, its 4th partial at C8 read as plus 35 cents), you enter 7. (Obviously when you enter the number, you have to go to the right note name and octave, and scroll cents up or down).
Is this clearer?
(BTW, David is referring, I believe, to some posts I sent to pianotech around ten years ago, when I was coming to terms with my SAT).
Regards,
Fred Sturm
University of New Mexico
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