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| Compensation and Scale Length http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=15368 |
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 3:07 am ] |
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Ya'll mind if I pick your brains a minute? I have a question about scale length that I just can't quite get right in my mind. Take for instance a 25.4 scale. Is the .4 actually a quarter inch? So 25.4 x 2 = 50 and one half inch? How does that work? I graduated high school in 1975 and have long forgot how to cipher….lol Okeh, next question…..for compensation of the saddle….I know you measure from inside nut (exactly where the string rests) to inside saddle, but how do you calculate the exact measurement to rotate the saddle in the bridge? Lets say if your low E string is resting off the twelfth fret 5mm, do you move your saddle back 5mm from the stop to compensate for the 5mm distance you have to move the string down? Which in turn would move the high E the same distance assuming the middle of the saddle is the pivot point. Hey, I just had an idea......or would you use the Pythagorean Theorem? you know, top of twelfth fret to bottom of string to saddle is a right triangle. From saddle back to fret is the hypotenuse. You could solve for "A" if you measured the hypotenuse and knew the string height. Is it really this complicated?
Anyhoo, I have all kinds of these crazy little thoughts going thru my brain. Hope you don’t mind if I throw a few out. |
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| Author: | DaveTaylor [ Mon Jan 14, 2008 3:23 am ] |
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The .4 is a decimal value - 4/10 of an inch. Which equals approx. 13/32 of an inch. |
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 3:36 am ] |
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[QUOTE=DaveTaylor]The .4 is a decimal value - 4/10 of an inch.
God bless you Dave, now my mind is at ease. I've done quite a bit of repairs on violins and notice almost every violin luthier uses the metric system of measurement. But, guitar building/repair is new to me and notice there is not much metric measurements in use. Could that be that United States is the leader of guitar building? Just an observation....now, where did I put my bending iron...... |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 4:05 am ] |
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The use of empirical inches on steel sting and electric guitars comes from the fact that most everyone adapted to Martin, Gibson and Fender scale lengths which of course being designed in the US where empirical inches was the standard unit of measure therefore it has been maintained as such. That said you can easily convert to millimeters. 1" is equal to 25.4mm. Now to really blow your mind. The Martin 25.4" scale length is actually 25.386" (if I remember correctly) but over the years became referred to as 25.4" for convenience and to simplify manufacturing dimensions. |
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 4:57 am ] |
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[QUOTE=MichaelP]The use of empirical inches on steel sting and electric guitars comes from the fact that most everyone adapted to Martin, Gibson and Fender scale lengths which of course being designed in the US where empirical inches was the standard unit of measure therefore it has been maintained as such. That said you can easily convert to millimeters. 1" is equal to 25.4mm. Being new to guitar building, do we really care or use the 25.4 measurement? When you fit the guitar for the bridge shouldn't you measure from the nut to the saddle position and then determine the correct placement of the bridge on the top plate? Why then must we worry ourselves about the 12th fret at this point? Only when we cut the fret slots should this be an issue. Am I way off here Michael? |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 5:09 am ] |
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Every thing starts with the desired scale length. This sets the distance from the inside edge of the nut to the (not yet-compensated) saddle. Then we have to account for the string tension and fretting effect. The is where the compensation comes from. As discussed in other topics the string core diameter at full tension is the big part of what sets compensation value. That really does not have anything to do with the scale length but rather has to do with making the string play at equal temperament at a given scale. I may be miss reading you comment but the scale length and therefore the 1/2 node or 12th position is Ox and comes before the compensation and intonation (the cart) You have to know the scale length before you can know the fret spacing or compensation value. |
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| Author: | Brad Goodman [ Mon Jan 14, 2008 5:15 am ] |
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Strnig gauge also effects compensation. |
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 5:19 am ] |
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Oh, that's right. Wow, I feel silly. 25.4 IS the string length and not the 12th fret position. I just been reading some old threads on this subject and it is really quite deep. I thought maybe there would just be a quick fix like "take a measurement somewhere" and waa laa, your saddle is perfect. You've been tons of help getting this thing lined out in my minds. THANK YOU! |
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 5:26 am ] |
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[QUOTE=Brad Goodman]Strnig gauge also effects compensation.[/QUOTE] Hey Brad, nice guitar you built there. That's what I'm working on now, a D-28 style. Anyhoo, I think this subject is kinda like discussing the varnish on Strads violins, it gets way too involved for my country boy brain. I think if the Martin Company wants to slot their bridges the way they do then it's good enough for me. I'll just glue on the bridge they sent....hopefully somewhere near where it is supposed to be....lol |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 5:53 am ] |
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Sting Core diameter sort of implied string gauge. but none the less. Yes |
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| Author: | KenH [ Mon Jan 14, 2008 5:57 am ] |
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Glad you got it sorted out Chuck! Welcome to the forum! It is highly encouraged on this forum to use your real name instead of a "handle". I am one of those people who is bilingual, so I speak Spanish as well. We are an International forum with members from almost every area of the world and some readers and lurkers may take offense to your choice of a screen name. Since you are new with not a long history of posts, and in as friendly of a manner as I can, I would like to suggest that you might rethink your choice and use your real name? Again, Welcome to the forum!! |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 6:09 am ] |
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Here again I do not want you to get confused. 25.4" is not the string length. At least not the actual string length between edge of nut and saddle contact. 25.4" is the non-compensated SCALE LENGTH or theoretical scale length as it were. If all the strings could be the same diameter and tension at pitch then yes the 25.4" would be the string length but as we know that is not the case. I am not trying to be nit-picking Rather being sure we do not confuse anyone. To say that 25.4" is the string length could miss lead a newbie into a false conclusion. 25.4" is the Theeoretical Design Scale Length. The base number the the fret spacing is calculated from. |
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 6:13 am ] |
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[QUOTE=Hodges_Guitars] Glad you got it sorted out Chuck! Welcome to the forum! It is highly encouraged on this forum to use your real name instead of a "handle". I am one of those people who is bilingual, so I speak Spanish as well. We are an International forum with members from almost every area of the world and some readers and lurkers may take offense to your choice of a screen name. Since you are new with not a long history of posts, and in as friendly of a manner as I can, I would like to suggest that you might rethink your choice and use your real name? Again, Welcome to the forum!! [/QUOTE] Thanks for the reminder Ken. I work in a prison in Southern Il and for some reason that is what the inmates tagged me with and it just stuck for a nickname for years. I'll square that away right now....now where do I go to do that....? Thanks for the open arms! |
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| Author: | KenH [ Mon Jan 14, 2008 6:23 am ] |
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You will need to register as a new user. Unfortunately, I dont think you can change your user name once it is in the system. Thank you in advance! Ken |
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| Author: | Ricardo [ Mon Jan 14, 2008 6:43 am ] |
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If you use a short scale like 24.9 and drop tuning like Open G should/could you use heavier strings? If I understand correctly, shorter strings need less tension, but to compensate for the lower tension can you use heavier strings? How does one compensate the saddle for heavier strings? Now I feel strung out!! 
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| Author: | Rick Turner [ Mon Jan 14, 2008 6:58 am ] |
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That would be "Imperial" not "emperical", please...not that I know why imperial comes from the concept of empire... Imperor's new clothes and all... See other thread, too... |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 7:32 am ] |
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 oops You are right.
Funny thing is our European Oil field clients are always giving us hell over dimesioning our drawings in feet, inches and decimal inches. I always remind them that it was they that gave us Imperial units in the first place 
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 7:33 am ] |
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[QUOTE=MichaelP]Here again I do not want you to get confused. 25.4" is not the string length. At least not the actual string length between edge of nut and saddle contact. 25.4" is the non-compensated SCALE LENGTH or theoretical scale length as it were. If all the strings could be the same diameter and tension at pitch then yes the 25.4" would be the string length but as we know that is not the case. Please Michael, I truely want you to nit-pick because I can tell you truely love what you do and enjoy sharing what you have learned. And I am willing to soak up every bit of knowledge you have. Gosh, Luthierie Schools cost thousands of bucks. You guys are great. I just want to say thanks for the patients. Okay, I just got out my plans for the Dreadnought and my measurements from nut to uncompensated saddle is 25.5 or 648.4 mm |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 7:54 am ] |
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If the plans show the saddle at an angle and not truly perpendicular to the centerline of the guitar then that dimension is compensated. I would guess your plans show the saddle in the compensated orientation or it would be misleading. One more time. The Scale length is a distance from the end of the nut to the end of the Theoretical (not accounting for compensation)scale. But before we locate the saddle we have to add the compensation to account for string behavior. The high or treble E string gets little or no compensation. The low or bass e string gets around .10-.13 of compensation. Now this is not intonation this is just compensation, or if you will pre-intonation saddle alignment. So if you measure a 25.4" scale guitar form inside the nut to the center of the saddle at the bass E it will measure some near 25.53" the treble E will measure some where near 25.38-25.41" |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 8:30 am ] |
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[QUOTE=MichaelP] If the plans show the saddle at an angle and not truly perpendicular to the centerline of the guitar then that dimension is compensated. I would guess your plans show the saddle in the compensated orientation or it would be misleading. One more time. The Scale length is a distance from the end of the nut to the end of the Theoretical (not accounting for compensation)scale. But before we locate the saddle we have to add the compensation to account for string behavior. The high or treble E string gets little or no compensation. The low or bass e string gets around .10-.13 of compensation. Now this is not intonation this is just compensation, or if you will pre-intonation saddle alignment. So if you measure a 25.4" scale guitar form inside the nut to the center of the saddle at the bass E it will measure some near 25.53" the treble E will measure some where near 25.38-25.41"[/QUOTE] Boy did I gooff that up no I dea what I was thinking at the time I wrote it. 
The sadle is compensated .1 at the high e and about .4 at the low E. High e will measure 25.5 + or -. Low E will measure 25.8 + or - |
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| Author: | Kirt Myers [ Mon Jan 14, 2008 8:37 am ] |
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Also, the distance from the nut to the 12th fret should be exactly half of your "Theoretical" scale length. So on a 25.4" scale the 12th fret would be 12.7" from the nut. Welcome Chuck. |
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| Author: | Michael Dale Payne [ Mon Jan 14, 2008 8:47 am ] |
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Yeper!!!! kind of critical but then again all the fret positions are !!!!!
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| Author: | Chuck Hutchison [ Mon Jan 14, 2008 9:16 am ] |
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[QUOTE=Kirt]Also, the distance from the nut to the 12th fret should be exactly half of your "Theoretical" scale length. So on a 25.4" scale the 12th fret would be 12.7" from the nut. Howdy Kirt, (shaking hands) Thanks for having me and for you knowledge of wooden stringed instruments...:) |
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| Author: | Jon L. Nixon [ Mon Jan 14, 2008 12:18 pm ] |
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Stew-Mac has a calculator on their website that gives compensated saddle placement measurements for any scale length. Might be a good place to start. |
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| Author: | JohnAbercrombie [ Mon Jan 14, 2008 1:51 pm ] |
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StewMac Scale Calculator |
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