Conversion neck question

[ocguy106]

The reason the conversion and the Gibson don't line up is because the 12th fret is in a different location then the 12th on the gibson. Think of it in reverse the bridge is in a different location  on a gibson and a warmoth. The nut can be moved up down anyway you want during manufacturing of the neck but the bridge will alls be in the same place so you take you measurement from there instead of the nut. the bridge on a 25 in scale sits slightly further back so if you just shorten the neck you will be out of intonation. The only constant is the bridge so you measure half the distance from there and set the frets accordingly and it my mind at least it would make sense that they don't line up with a gibson.

Not sure if I explained that right

 

[drewfx]

Conversion necks just have to do with the heel of the neck vs. the position of the bridge. Nothing more to it than that.

The distance between the nut and bridge, and the fret spacing, is always the same for any scale length. If the fret spacing is different, it's because the scale length is different and has nothing to do with conversion necks. As swarfrat posted above, Gibsons have had varying lengths even though they are commonly called 24.75" today.

Normally, shorter scale instruments have the bridge located closer to the neck pocket (for better upper fret access) and longer scale instruments have the bridge further from the neck pocket (less neck dive). A conversion neck just adapts to the longer scale length bridge position by changing the location of the frets relative to the neck pocket.

 

[NQbass7]

http://www.stewmac.com/freeinfo/Fretting/a-scalelength.html
Gibson
The Gibson 24-3/4" scale is also very common, but it is also the most confusing of all scale lengths—this is because it rarely ever measures out to be 24-3/4 inches! This scale has gradually changed over the past fifty or so years due to changes in production equipment.

It won't change the lineup of the frets, but intonation adjustments are actually changing the scale length a tiny bit to compensate for things like string inharmonicity (bridge compensation) and pitch change due to tension required to fret the string (nut compensation)

Well that explains it... apparently the Gibson is shorter scale than the warmoth neck, hence the frets on the Warmoth neck being farther from the nut.

The reason the conversion and the Gibson don't line up is because the 12th fret is in a different location then the 12th on the gibson. Think of it in reverse the bridge is in a different location  on a gibson and a warmoth. The nut can be moved up down anyway you want during manufacturing of the neck but the bridge will alls be in the same place so you take you measurement from there instead of the nut. the bridge on a 25 in scale sits slightly further back so if you just shorten the neck you will be out of intonation. The only constant is the bridge so you measure half the distance from there and set the frets accordingly and it my mind at least it would make sense that they don't line up with a gibson.

Not sure if I explained that right

On any scale, the 12th fret must be exactly half the scale length from the nut, always. On a 24 3/4" neck the 12th fret is 12 3/8" from the nut, on a 28 5/8" baritone neck it's 14 5/16" from the nut, etc. The only way frets don't line up is if the scale length is different, and as swarfrat pointed out above, that's what it is in this case: the Gibson doesn't actually have a 24.75" scale length.

 

[Cagey]

On any scale, the 12th fret must be exactly half the scale length from the nut, always. On a 24 3/4" neck the 12th fret is 12 3/8" from the nut, on a 28 5/8" baritone neck it's 14 5/16" from the nut, etc. The only way frets don't line up is if the scale length is different, and as swarfrat pointed out above, that's what it is in this case: the Gibson doesn't actually have a 24.75" scale length.

Good to know we aren't stuck in some weird guitar Twilight Zone, eh?

 

[NQbass7]

On any scale, the 12th fret must be exactly half the scale length from the nut, always. On a 24 3/4" neck the 12th fret is 12 3/8" from the nut, on a 28 5/8" baritone neck it's 14 5/16" from the nut, etc. The only way frets don't line up is if the scale length is different, and as swarfrat pointed out above, that's what it is in this case: the Gibson doesn't actually have a 24.75" scale length.

Good to know we aren't stuck in some weird guitar Twilight Zone, eh?

Yeah, real physics effs with my head enough as it is, without stuff I thought I knew going weird too.

 

[bagman67]

Good to know we aren't stuck in some weird guitar Twilight Zone, eh?

You may be overstating the case.

 

[Cagey]

Yeah, real physics effs with my head enough as it is, without stuff I thought I knew going weird too.

No kidding.

 

[Cagey]

You may be overstating the case.

Hehe! Yeah, maybe.

 

[swarfrat]

Four tries and they STILL couldnt get a decent bridge on that guitar!

 

[Cagey]

I take it you're not a big fan of TOMs, either?

 

[djmarcelca]

K guys I'm pretty sure I got it now.

 

[veemoth]

One thing i may still be a little confused about...why choose one scale neck over another?
Do they sound different? eg on a Warmoth body you could put a LP ("Wing") conversion neck..or a non conversion one           
(you can see i've been eyeing those last few LP bodies coming through!!)
What's the difference in sound? Or is it playability?  :icon_scratch:

 

[AutoBat]

The sound will be nearly the same, it's the feel that changes due to the string tension difference.  If you snag a last run LP body you can use a 24.75" conversion neck, a 25.5" Pro, or heck, you can stick a 28.625" baritone conversion neck on it if you're up to it. (This one will sound & feel different, I'd reckon).

 

[veemoth]

So... Longer scale = "tighter" strings??

 

[AutoBat]

Short answer: yes.
Closest approximation that I usually read is that you can go up a string size when going down from 25.5 to 24.75 to keep about the same string tension.

I've only ever played 25.5" so I don't have any personal experience to imbue upon the subject.

 

[Ace Flibble]

So... Longer scale = "tighter" strings??

Same strings, same tuning, same bridge style and same nut/headstock? Yes, longer scale will give more tension.

But really, there is more to string tension than just the scale length. Tune-o-matic and stopbar bridges are great examples. If you string it up normally, with the stopbar all the way down, you get more resistance when bending a string than if you 'topwrap' the stopbar, or raise the stopbar up. The strings are the same, tuning the same, headstock/nut the same, scale length is the same. Tension when picking a note and simply holding it is exactly the same. But the break angle over the bridge saddles has changed, so you get less tension when bending.

Yes, it's confusing.


Best thing to do, when it comes to working out what spec to go for, is ignore the science, ignore the theory. Just think about the guitars that you've played that have been most comfortable for you and copy their specs. There's no point guessing at what might be best, buying something because somebody on the internet told you what they like best or experimenting. These things cost a lot of money and if you're buying anything custom then you should already have a good idea of what feels best in your hands, anyway. Stick with what you know you'll like.

 

[AutoBat]

Best thing to do, when it comes to working out what spec to go for, is ignore the science, ignore the theory. Just think about the guitars that you've played that have been most comfortable for you and copy their specs.

Well said.

 

[djmarcelca]

OK soo, after this thread was dead and gone, I looked around and bought a couple of Guitar building books and this is what I eventually found out:

What makes a conversion neck a conversion neck is.................(drumroll sound effect)

Re-positioning the nut.

Here's the theory:
It works like a capo.
Put a capo on the first fret you've shortened your scale or converted it.

To change a fretboad scale on a guitar that was build for something else:
Reposition the nut.
From 25.5 - 25 scale move it 1/2 inch CLOSER to the bridge.
From 25.5 - 24.75 Move it  3/4 inch Closer to the bridge.

That's simplified explanation.
You still have to determine the correct bridge/nut/12th fret ratio, but by moving the nut closer and measuring the fret spacing etc, etc, etc.

That's what make a conversion neck a conversion neck.
Nut repositioning.