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Thread: (Another) Intonation Question…

  1. #11
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    OP - First reply.
    I'm honored by the number of replies and the wisdom you've shared. To @anthonyg you've fulfilled my need-to-know and delighted my curiosity. I'll add to this reply shortly ( Currently 9:30 am CST ). I've made a number of measures to the three instruments and the results dovetail ( not rabbit tail ) to what he's shared in his diatribe.

    If I have one regret is that I failed to make one point clear. My interests have to do with asking "why" and not looking for perfection. It's clear from reading the dozens of posts on intonation that there is no 'perfect.' Two 'ukes from quality makers that received "full" setups, and one from a mass production vendor with no setup. The later doesn't display the large range of increasing "flatness" of the former. I am/was curious as to why the flatness occurs, and from it, what could be changed to improve the two to the level of the Montecito. While I'm not in the OCD universe, over the decades I've learned that failing to look down a rabbit hole can make you blind to understanding, alternatives, and solutions. :-) Thanks again, more detail info to follow.
    Stu

  2. #12

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    I want to give props to anthonyg for the concise and detailed information....very well explained.

    No matter how far down the rabbit hole you want to go (as that is a personal choice) you have provided a great deal of experiential knowledge and insight to getting folks where they want to be.
    I personally don't mind all the details and accuracy. The way I have approached ukulele building (or any instrument I make) is that knowing that perfection is unobtainable, means I need to be as accurate as I can to get as close as I can when it all comes together. As a minuscule amount here and there can in some cases add up to a problem later on.

    A specific detail may make no discernible difference to one person but that does not mean it is the same for another. As an example: My son has been apprenticing as a sound engineer for a while now and he is recording a bunch of songs I have written over the years to keep his gears rolling in between gigs. We will be listening to playback and he hears and notices things that I cannot even hear. So what does not matter to me, bothers him. So, I just have him do what he needs to do to feel good about it and everyone wins.

    So I would say that if you want to be close and do not care about going all the way because you cannot tell the difference, no problem, just do it to your liking (or ability) and round off that 0.2mm difference. It will definitely be better than the crappy factory non-set up you get with most cheap ukuleles. But if you want to go all the way, then get as accurate as you can all the way through.

    However, I think the more important point is that if you round off the 0.2mm on your first measurement you may miss the fact that the problem is at the nut and not the saddle or a fret that was misplaced, etc.. So I would say that the main point is that you take as accurate of a measure as one can of all these aspects before you break out a file..... I too have learned this one the hard way in the past.

    No matter what you choose the point is to be happy with the results and that is what matters.

  3. #13
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    OP here - followup ( 3:40 CST )
    Intonation Measures.
    Part two.
    Using the StewMac calculator suggested by “anthonyg” (thank you!), a digital caliper, and a metric scale 400mm ruler I took measurements
    1)of the scale,
    2)at the twelfth fret, plus;
    3)measurements from the nut to frets 1,2,3,4,5,6,7. (using the digital caliper)
    4)measurements fret-to-fret at nut-1, 4-5, 6-7, 9-10, 11-12 (using the digital caliper)

    Both the Romero STC and Replica have “factory” compensated saddles for the C and E strings, set back slightly more than 1.0 mm.

    First, the Montecito tenor. (gCEA uncompensated saddle) Scale: 381+ 12th Fret 215.5
    Fret measurements up to the 7th fret were within 0.5% of the StewMac Calculator
    Fret measurements BETWEEN frets were generally over 0.5mm - very close

    Second, the Romero Replica tenor 18 frets (compensated saddle for the C and E strings)
    Scale length for the G and A - non-compensated strings 433mm with 12th fret at 215.5
    Scale length for the C and E - compensated strings 434.5mm with 12th fret at same 215.5
    Nut to 1st fret was short by 0.3mm ( 24.302 v. 23.975 )
    Nut to 5th fret was short by 0.87mm ( 108.993 v. 108.12 )
    Nut to 7th fret was short by 1.15mm ( 144.506 v. 143.36 )
    Difference in fret-to-fret measures were scattered. Three were over .25, three minimally below zero.

    Third, the Romero STC As with the Replica, it has a gCEA uncompensated saddle. Promoted as concert scale on a tenor body and 22” in total length. The fret board scale is 380mm (g and A), and 381mm (C and E).
    Scale at the 12th fret is 187.5mm and the scale is 15 ( and 1/2 ) frets (half the 16th fret is removed over the sound hole. When I tried to use the StewMac calculator the results didn’t make sense so I didn’t go into comparative measurements.

    With both the Romero’s having bridges/saddles exceeding the half-way measures to the long side, intonation going flat when moving up the fretboard makes sense. This exercise has helped me understand the relationship, especially when the number support the very helpful description that “anthonyg” detailed (thank you AGAIN).

    I highly doubt that I would do anything with the Replica. I rarely play that far up on a tenor. But I’ll have to think further whether to have something done with the STC. It’s noticeably flat, even to my ‘senior’ ears. When I have more time I’m going to do the same nut-to-fret measurements on it to see how it differs from another concert that I have (which doesn’t have similar issues).

    Thanks again to those who contributed to my journey :-) I hope others can use the information for their better understanding as well. And if anyone has some additional thoughts, please share. This is a great forum to learn.
    Stu
    Last edited by Web_Parrot; 05-21-2019 at 10:42 AM.

  4. #14
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    Just to make my position clear, I have no issue with AnthonyG's explanation of the relationships of nut, frets, and saddle, and the need for compensation at the saddle. All that was clear and concise, and will be very helpful to anyone who has not studied these matters.

    What I take issue with is the advice to measure these relationships with a steel rule, expecting to do so to an accuracy of two tenths of a millimeter. Tell me - how thick are the markings on your steel rule?

    My eyesight is pretty good. I reckon I can measure to about of one third of a millimeter, using a steel rule, but less that a quarter of a millimeter?

    No way!

    John Colter.

  5. #15
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    I'm glad I could help and those are some impressive measurements.

    I should clarify things as you've probably done more measurements than you need to do.
    What all those nut to fret measurements have shown is that the nut IS too close and its a matter of filing it or shimming it back.

    You only really need to do one nut to fret measurement and thats the centre of the 12th fret to inside the nut. For this measurement to make sense though you first MUST know the precise scale length that the frets are fretted for.

    TO do this I'm recommending calculating the 1st fret to 12th fret and 1st fret to 16th fret distances and then measuring them to see if they're accurate. If there a little out then adjust the figures on the calculator and do it again. You most definitely will have variances between a nominal Imperial scale in inches and its closest metric equivalent.

    Is a Tenor 17" (431.8mm) or metric 432mm. Is a Concert 15" (381mm) or 382mm. Is it 19" (482.6mm) or just 482mm.
    When you KNOW what the frets are then you can just measure from inside the nut to the centre of the 12th fret.
    More measurements can be used to see how accurate all the frets are though.

    When the nut is placed spot on in relation to the frets then 2mm +/- a fraction of saddle compensation is pretty good. A tiny bit of compensation at the nut can be good (0.3mm closer approx) but if's going flat its going flat. If so then file it back.

    If the material on the nut or saddle is there in the right spot then it can be adjusted. Its a damn sight harder to "adjust" into thin air.

    EDIT. Also I should add.My experience is that a 1mm gap from the nominal scale length to the leading edge of the saddle is right. The needed saddle compensation should fall somewhere on the saddle material. Its a matter of fine tuning. If the required compensation isn't falling on that saddle then look for an error in the nut.
    Last edited by anthonyg; 05-21-2019 at 05:16 PM.

  6. #16
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    Quote Originally Posted by ukantor View Post
    Just to make my position clear, I have no issue with AnthonyG's explanation of the relationships of nut, frets, and saddle, and the need for compensation at the saddle. All that was clear and concise, and will be very helpful to anyone who has not studied these matters.

    What I take issue with is the advice to measure these relationships with a steel rule, expecting to do so to an accuracy of two tenths of a millimeter. Tell me - how thick are the markings on your steel rule?

    My eyesight is pretty good. I reckon I can measure to about of one third of a millimeter, using a steel rule, but less that a quarter of a millimeter?

    No way!

    John Colter.

    John, I agree that these measurements are hard to make accurately and taking centre fret to centre fret measurements is particularly difficult. This in no small way is why I am specifically instructing people to do the calculations first based on an educated guess and then lay the rule on the frets. Measuring the frets first and then trying to compare them to the stewmac calculator's data will give nonsense results.

    You will see a difference though in a 0.2mm adjustment. One will look closer than the other. The difference between 482.6mm and 482mm was easy to spot.
    Also definitely do at least two LONG measurements. Trying to measure from fret 1 to fret 3 will also give nonsense results.
    Last edited by anthonyg; 05-21-2019 at 05:18 PM.

  7. #17
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    My final notes:
    Just some clarification on my measurement process. First, I used a digital caliper for the nut-to-fret for frets 1 thru 9. To get the center value for the frets, I sampled the thickness of a few frets (using the caliper) and divided the value by 2. I then measured from the nut to the nut-side of each fret, then added the half-value to get the distance to center. For the fret-to-fret values I simply measured top edge to top edge using the presumption that the frets were near similar thickness (edge to edge = center to center).

    As for the remaining measurements I used an etched Machinists’ metric ruler, certified accurate to 0.5mm ( Start brand ). Where a value ‘mark’ fell between the etched markings I simply interpolated the value to 0.25. Any values not in multiples of those are a result of adding the half-fret measurements to the ruler reading.

    I’ve attached a scanned copy of my worksheet for the Romero STC. If I’ve correctly understood the responses here, the values at the 12th fret are larger than they should be and probably causing the “flat” Cent reading and noticeable (to my ear) out of tune. While it might seem I’ve taken this to an unnecessary level to affirm that conclusion :-) …. I wanted to learn a lot and truly did! Thanks to everyone for sharing their knowledge and opinions.
    (ps-I’ve also learned to ‘author’ my replies in a word processor and “paste” the reply into the forum. It doesn’t like me and has bumped me out without saving!! grrrr)

    Romero STC Measurements.jpg
    Last edited by Web_Parrot; 05-22-2019 at 08:12 AM. Reason: Technical delay... image to large to upload.... grrr

  8. #18
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    Quote Originally Posted by Web_Parrot View Post
    My final notes:
    Just some clarification on my measurement process. First, I used a digital caliper for the nut-to-fret for frets 1 thru 9. To get the center value for the frets, I sampled the thickness of a few frets (using the caliper) and divided the value by 2. I then measured from the nut to the nut-side of each fret, then added the half-value to get the distance to center. For the fret-to-fret values I simply measured top edge to top edge using the presumption that the frets were near similar thickness (edge to edge = center to center).

    As for the remaining measurements I used an etched Machinists’ metric ruler, certified accurate to 0.5mm ( Start brand ). Where a value ‘mark’ fell between the etched markings I simply interpolated the value to 0.25. Any values not in multiples of those are a result of adding the half-fret measurements to the ruler reading.

    I’ve attached a scanned copy of my worksheet for the Romero STC. If I’ve correctly understood the responses here, the values at the 12th fret are larger than they should be and probably causing the “flat” Cent reading and noticeable (to my ear) out of tune. While it might seem I’ve taken this to an unnecessary level to affirm that conclusion :-) …. I wanted to learn a lot and truly did! Thanks to everyone for sharing their knowledge and opinions.
    (ps-I’ve also learned to ‘author’ my replies in a word processor and “paste” the reply into the forum. It doesn’t like me and has bumped me out without saving!! grrrr)

    Romero STC Measurements.jpg
    You've done some great work and I applaud you, however you missing one of my points.
    Before this work makes any sense you first must establish the actual scale length of the frets, WITHOUT using the nut as a reference point. This is very important.
    Just how did you decide that the nominal scale length was 380mm? Its more likely to be 381mm or 382mm and in this scenario all your figures will be low as they are.

    So, first things first. Using the 380mm scale length data, calculate what the distance from fret 1 to fret 16 will be. Calculate what the distance from fret 1 to fret 12 will be.
    Do the distances line up or are they short of the mark? Try 381mm and try 382mm doing the calculations again. Which looks closer? It might even be something else.

    Yes. These distances are outside the range of your digital callipers so I do understand why your doing it your way but there is method to my madness. You try out a few and one will look right or the closest.

    This is importantly the first measurement to make/confirm.
    Once the scale is established independently from the nut then its a simple measurement from inside the nut to the centre of the 12th fret to establish the nuts placement.
    The work you have done is checking the accuracy of the fretting yet its giving you false data until you have established the correct scale length independently from the nut.

    Its all learning yet I have stated multiple times that you need to measure fret 1 to 12 and fret 1 to 16. This is key. This is first.

    EDIT: OK, for the record I AM using reading glasses for checking scales and I have a strong set just for getting up close as well. These are cheap reading glasses. Nothing prescription.
    Last edited by anthonyg; 05-22-2019 at 02:23 PM.

  9. #19
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    Quote Originally Posted by Web_Parrot View Post
    My final notes:

    (ps-I’ve also learned to ‘author’ my replies in a word processor and “paste” the reply into the forum. It doesn’t like me and has bumped me out without saving!! grrrr)

    Romero STC Measurements.jpg
    This is sage advise. Apart from losing partly written posts, I have also lost lengthy documents when submitting (not to this forum). Apparently with some forum software, if two posts are submitted simultaneously, one is preferentially accepted and the other may be lost to the 'ether'. This should not happen but it sometimes does .... I have been an unlucky victim on a few occasions now, so if my posts are to be more than a few sentences, I also use a word processor.
    Last edited by bazuku; 05-22-2019 at 06:53 PM.

  10. #20
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    Default FollowUp Clarification (widen your viewing screen for best data layout)

    Quote Originally Posted by anthonyg View Post
    You've done some great work and I applaud you, however you missing one of my points.

    Its all learning yet I have stated multiple times that you need to measure fret 1 to 12 and fret 1 to 16. This is key. This is first.
    .
    :-) Your points were not overlooked, but perhaps my cut n’ paste effort failed to include the scale info as intended. I've captured the information, re-measured both the Romeros (see [Note*] ), and presented in a format that makes it easier to compare.
    All my measurements are metric. I’ve re-measured both my Romero’s

    “actual” nut to saddle measurements for the Romero STC: g-@-380mm C-@-381mm E-@-381mm A-@-380mm
    Saddle is a factory compensated (C&E) and I measured from the point on the saddle where the string first breaks over the bridge after emerging from the bridge.

    Fret to fret measures:
    *Ctr of 1st to 12th frets@ 166.5mm = Ctr 1st to 16th frets@ 205mm => diff 38.5mm
    StewMac (381mm) 1-12 = 169.120mm 1-16 = 208.42mm => diff 39.3mm
    StewMac (382mm) 1-12 = 169.560mm 1-16 = 208.96mm => diff 39.4mm


    “actual” nut to saddle measurements for the Romero Replica RCR: G-@-433mm C-@-434.5mm E-@-434.5mm A-@-433mm Saddle is compensated (C&E) and I measured from the point on the saddle where the string first breaks over the bridge after emerging from the bridge.

    Fret to fret measures:
    *Ctr of 1st to 12th frets@ 191.5mm = Ctr 1st to 16th frets@ 236.0mm => diff 44.5 mm
    StewMac (431.8mm) 1-12 = 191.650mm 1-16 = 236.21mm => diff 44.56mm
    StewMac (432.0mm) 1-12 = 191.740mm 1-16 = 236.31mm => diff 44.57mm

    So… choosing the StewMac calculator imperial scales for both comparisons ( 15” and 17” respectively ) I compared my original measurements, nut-to-fret, at the 1st, 5th, and 12th frets.

    STC (15”) @ Nut to 1st -> 20.97mm 15”scale -> 21.384mm
    Nut to 5th -> 93.96mm 15”scale -> 95.573mm
    Nut to 12th -> 186.2mm 15”scale -> 190.500mm

    RCR(17”) @ Nut to 1st -> 24.00mm 17”scale -> 24.235mm
    Nut to 5th -> 108.2mm 17”scale -> 108.316mm
    Nut to 12th -> 216.0mm 17”scale -> 215.900mm

    With this added clarity :-) I’m interested in any supporting conclusions that have become more obvious.
    Thanks TONS (metric, of course) for your time and expertise and guidance.

    [*Note: Centre to Centre measurements were actually taken from the top edges of the frets with the ruler carefully registered against the edge. All the frets appeared to be similarly crowned so I’m resuming the relative point to point measurements are pretty close!.]
    Last edited by Web_Parrot; 05-23-2019 at 08:24 AM. Reason: formatting

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