Can someone tell me what the exact measurements are between the face of the nut and front edge of the saddle for both E strings on a Gibson acoustic with a 24-3/4" scale, please?
I want to know how far mine may be off from the factory standard.
Measure from the inside face of the nut to the center of the 12th fret, add 1/8 to 3/16 inch to that measurement and that is the distance from the center of the 12th fret to the front of the saddle on the bass side. Add 1/32 to 1/16 inch to get the length from the 12th fret to the front of the saddle on the treble side. Larger strings and higher action will need the larger amount of compensation. Low action and light strings will need the smaller amount of compensation.
There's not a single definitive answer to that question. Aside from there being a fair range of saddle compensation which could be considered "correct" (suitable area in the saddle footprint to shape individual string compensation within), their '24_3/4"' scale (and even their fret spacing method) has varied quite a bit over the years.
Short of delivering actual definitive numbers though, follow the method and compensations Harrison described for measuring your individual instrument. Those standard compensation ranges should be a good place to start.
Out of curiosity, what is the year and model of instrument in question?
Ah, well there you go. They used an entirely different (and notably irregular) fret spacing system before '48, then another system from then through the 80's, and then finally joined the modern world on fret spacing math with their Bozeman acoustics (not quite there on their electrics yet though).
All my data is on my other computer at the shop, but I know I have board measurements from at least one SJ of that era on file. For now I can at least tell you that the 24_3/4" scale of the early 40's was longer by at least 1/8"-3/16" than the 24_3/4" scale they use today, if that makes any sense.
It's worth noting that even if the saddle is in the correct position to intonate well at the 12th fret, it will still have some intonation quirks elsewhere around the board simply due to the irregular fret spacing.
I find this an interesting observation,David! I own a '48-'49ish SJ. I will make an effort to take some measurements to contribute to the mix!
I meant to say its a '47-'48ish SJ The FON is 731
actually FON 831....correction. I still ponder Davids theory/testimony. I measured my SJ this evening.
The low-E (nut to bridge-saddle) measures 25" and high-E(nut to bridge-saddle) is 24-14/16"!
All intonates well with Med/Light strings.
I didn't intead to hi-jack Michaels' thread but only hoped to 'add-to'..!
Long day, sorry about the late reply.
The '43 SJ I thought I had on file was actually a 1950, but I do have five other short scale Jumbos in the 41-43 range, and they are rather consistent. Relative scale length (nut to 12th fret x2) seems to fall predictably in the 24.75"-24.765" range in this era, averaging at about 24.76".
This means if yours is consistent with one's I've measured from this era, the front of your saddle slot should ideally fall somewhere around 24.790 at the high E, and 24.930" at the low E, give or take a few tens of thousandths here or there. I assume this is not the original bridge on this instrument?
How does it sound intonation wise, and if there are any glaring problems, where specifically are they? Gibson's frets were spaced to a very irregular / non-logarithmic system during this time. Even if the 12th fret intonation is perfect, you can end up with some slightly flat zones in the lower frets (2-4, 9-11), and sharp above the 12th (save for 16-18). It's a befuddling system to figure out mathematically, but at least it's consistently befuddling.
Rod, your's is almost certainly after they changed their spacing to the rule of 18, (literal 18, not 17.817). The early examples of this through the early 50's seem to have been calculated from a base number of 25, which when using an even 18 divisor leaves you with the equivalent of about a 24.8" scale. Ever so slightly longer than the pre-47 boards, and notably longer than the boards from 52-53 onward. Intonation on these boards is generally just fine, with the exception of some exacerbated sharpening on the uppermost 3 or 4 frets, but who plays complex chords up there where you could ever notice a problem anyway? :)
Well I think you're on the right track - those measurements indeed sound way off for that guitar. I imagine that would be notably sharp across the board, from a at least 6-8¢ at the first and up to 20-30¢ sharp as you approach the upper frets. That's a pretty sizable error that would present a challenging hurdle for anyone to tune and play around.
Of course always do no harm in terms of preservation on a fantastic instrument like this, but it certainly sounds like it needs to be moved and is not likely the original bridge anyway. I agree that the "Intonator" is entirely unnecessary for this job, but the saddlematic can be a very useful tool. Beyond that, you can only fine-tune to a realistic level of precision on these, most of which can be done with ears and sometimes a good tuner a bit of math.
Measure twice, cut once, but it certainly sounds like the saddle needs to be relocated. I've never personally measured a board from that era that would work with the saddle position you have there.
Go to stewmac and purchase the The Intonator and you'll always know the perfect measurement. It's a great investment. Just a thought. Check out the attachment.
Yes, StewMac has lots of cool goodies most of which are hard for me to justify for the rare one-off jobs on my own instruments.
We also have no luthiers within 2 hrs.