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Gibson Songwriter Deluxe

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On 17/02/2018 at 11:42 PM, Crusader said:

I'm wondering if they are like a Les Paul and don't measure half the scale length to the 12th fret

Source? If the nominal scale length isn't twice the distance of nut-to-12th, then the guitar is what is known as 'broken' :D


1 hour ago, Crusader said:

321mm to 12th fret

So about 12.63", or nominal scale length (before intonation compensation is applied) = just shy of 25.25"

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Even so, a scale length where the 12th fret does not fall at half the string length would mean that the most critical string division (the octave) would be out of tune. There are several fret calculations in use for a normal 12-tone guitar, 12th root of 2 being the most common, but I think they all rely on the octave falling at exactly the midway point on the string.

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But the only fret calculation where the 12th fret is half the scale length is when you use the 12th root of 2

If you take any guitar, the only string that intonates all the way up perfectly is the first string. On a Gibson it doesn't, it reads high above the 12th fret. If you set it to intonate at the last fret it will be around -2 or -3 cents for most of the fretboard

But we have gone off-topic now. I just wanted to know if Gibson use the same or similar calculations for their acoustics as their solid bodies. It is common knowledge that Les Pauls have a strange scale length and it is mentioned quite a bit around the internet. Well it was several years ago

One guy reckoned that Gibson use 24 9/16 scale up to the 12th fret then 24 3/4 after that. I found it actually seems to work, but I mentioned it in a post several years ago and one of the members here Swedish Luthier pointed out "No, they just use a different number in the calculations" I had already tried that in the 90's but I thought there was too much discrepancy between my measurements and calculations

But any way as stated its gone off-topic. Check the intonation on a few guitars. You will find that most will be flat above the 12th fret but a Gibson will be sharp. (Don't use a clip-on tuner though)

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Interesting topic though ;)

Yes, you're right. Looking more at the background into this it seems that Gibson may have used at some point in their operations the rule of 18 for fret placement, which positions the 12th fret slightly closer to the nut than scale length/2. Although there is a lot of conjecture floating around as to whether it was ever officially rule of 18 or just a sloppy implementation/approximation of 12th rt/2 (aka rule of 17.817) that just worked...or something else entirely...

Calculating the fret placement in Excel illustrates what the difference is between the two methods. The octave fret on the Rule of 18 method is a 10th of an inch closer to the nut when the scale length is 25":



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Here are my measurements of a 1997 '61 Reissue SG and a 2014 '59 Reissue Les Paul compared to the 1/18th Rule and to standard formula. Note the SG has a misplaced 5th fret

Column A is my measurements

Column C is 1/18th Rule worked out with 628.65mm (24 3/4 inches)

Column E is standard 12th root of 2 formula using the nut to 12th fret doubled for Scale Length

Column B is my measurements compared to the 1/18th Rule

Column D is my measurements compared to the standard formula using 12th root of 2


1997 '61 Reissue SG



2014 '59 Reissue Les Paul



As you can see, they match the 1/18th Rule better than the standard formula. I also have a 2013 ES-137 that matches just the same


And here's a video on the topic too


There are also other videos from this site, very interesting




Edited by Crusader
better diagrams
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I assume your measurements were made straight up the middle of the fretboard (ie, perpendicular to the frets)?

You've used measured 12th fret and doubled it for scale length, but your comparisons between measured spacings, Rule 18 spacings and 12th rt/2 spacings are all re-compensated to the 12th fret distance, which tends to lessen the apparent difference between Rule 18 and 12th rt/2. Your two scale length cells (C28 and E28) show the actual scale difference between the two methods when calculating from the fret spacings backwards, which is opposite to the way it would normally be worked out in practice.

Interesting findings nonetheless.

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  • 2 months later...

I fitted a door on a recording studio the other day and the guy had a Hummingbird. He let me measure the frets and I also measured the frets on my recently acquired Songwriter, so for what its worth

The Songwriter is 25.3 inches

The Hummingbird 24 5/8 inches

Both calculated by the 12th root of 2 (1.0594631)


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