Any Luthiers? Help with Guitar Intonation.

G

Guy McVer

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Mar 22, 2022
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Was gonna post this in Community Center where it would get more eyeballs, but I guess it belongs in Gadgets and Gear (according to the pinned "read before posting" thread).

So I bought a crappy no-name acoustic guitar at a thrift store. It cost basically nothing, so I grabbed it thinking I could experiment with fixing it up. I thought it would be a great chance to tinker with it and learn something.

After putting on a new set of strings (the strings were free so I didn't waste any money), the first thing I noticed was that the guitar's intonation was all wrong. So I measured the distance from the nut to the 12th fret and then to the saddle, and both distances were *roughly* the same. Hmmm.

But then I realized, "oh, it has a zero fret, so I should actually be measuring from there instead of the nut". I think this is the reason for the bad intonation. When the open strings are tuned perfectly, fretted notes are too high. This would theoretically be because the zero fret is in the wrong position. Right?

So I got to thinking, "what if I just removed the zero fret?" Or better yet, what if I just sanded it down so it's level with the fret board? Wouldn't that fix the intonation? Of course I'd have to replace the nut, or maybe put a shim under the existing nut it to raise it up a little?

Or would all the other frets now be in the wrong position once the zero fret is removed? The distance between the nut and the first fret is nearly a quarter of an inch longer than the distance between the zero fret and the first fret.

Any thoughts?
 
Well it looks like I'm going to end up answering my own question. 😞

After doing a little more digging into this, I think what may have happened is that when they built this guitar, they positioned the bridge based on the nut instead of the zero fret. For some stupid reason, I was measuring down to the 11th fret instead of the 12th fret. So it's even worse than that. The bridge is in the wrong position even if you were to calculate the scale length based on the nut. Doing the measurement by starting from the zero fret also has the bridge is in the wrong position. Both measurements end up with a scale length calculation which doesn't match the current location of the saddle.

What I think I need to do to fix the intonation is move the bridge. Obviously it's glued in place, so I have to get it off first and then re-glue it farther up farther down the main body of the guitar. I believe that might fix the problem.

Thankfully it's a pinless bridge. I don't have to drill a new set of bridge pin holes because there are no pins.

Here is my reasoning: If I calculate the scale length based on the zero fret instead of the nut, it gives me a shorter length. The saddle is only in the right position if you calculate the scale length based on the nut The saddle isn't even even the correct position if you base the scale length from the nut, which theoretically would be wrong anyway because there is a zero fret which marks the actual start. Whenever there is a zero fret, it's not the nut that marks the start. It's the zero fret.

Right? 🤔

Any thoughts? Tips? Advice?

edit: So the bridge definitely needs to be moved. It's just that I did my measurement wrong because I'm an idiot.

Instead of going farther up, the bridge needs to go farther down. The bridge is definitely in the wrong place though. That much seems certain whether you're basing it off the nut or the zero fret.
 
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There are really no luthiers around, huh? I would have figured there'd be at least one or two. 🤷‍♂️

Well, I checked the fret spacing with an online calculator, and it seems accurate enough. So whichever chinese factory that slapped this thing together at least appears to have gotten that part right, even if they did put the bridge in the wrong place.

I've masked off the new bridge position, and at someone else's advice, I'm going to sand it a bit to rough it up and give the glue something to grab onto. As for the previous bridge location, after I finish cleaning it up, I'll probably end up just slapping a sticker over it. This is a cheap guitar after all.

One slight problem is that the bridge plate doesn't extend all the way to where the bridge screws would go in the new bridge location. Based on some of the stuff I've been reading on various guitar forums, I don't think that the bridge screws are really necessary, and I've seen plenty of guitars without them. The sound hole is too small for me to be able to reach far enough inside anyway, and so I'll just glue the bridge down without the screws and it *should* hold. 🙏 I will only be using cheap light tension strings on it, so I suspect that it will be just fine.

Oh and instead of titebond or hide glue, I'll be using epoxy, once again following some advice I got from someone. It should be even stronger, and the only objections I was able to find to using epoxy was that it would make future repairs more difficult because epoxy isn't easy to remove. Well, so what? That's not exactly a problem for a cheap guitar, so who cares? I certainly don't.

Anyway, I think that I've already gotten what I wanted out of this guitar. It has definitely been a learning experience.

Here goes nothing. Wish me luck. 🤞
 
Well, it worked. :p

And by that I mean the intonation is basically fixed now. Moving the bridge lower down was the right thing to do. It actually plays like a normal guitar now! And it doesn't sound half bad either!

There is one slight problem though... :rolleyes:

Because this was my first time trying something like this, I glued the bridge a little too far to one side. So now the top string is a bit too close to the edge of the fretboard. It still plays fine but it's annoying. So I think I am going to have to pull up the bridge up again and re-glue it. 🤣

But this time I already have everything figured out and I know the procedure, and I think I know how to avoid the placing bridge off-center. It happened because I used to much glue and I couldn't quite see where the bridge was supposed to line up. The next time I'll do it better.

Oh and I used Titebond (original), which means that the glue should come back off a whole lot easier than if I had gone through with using epoxy. I'm glad that I changed my mind about that at the last minute!

I think I have learned a lot. Most importantly, I know that I definitely don't have what it takes to be a luthier. But this was fun.
 
Sorry I just saw this thread. Not a Luthier, but a decades long player and gigger. I tend to do my own maintenance as well.

You did good. It's just math, really. There is a parts supplier named Stew Mac who has many repair tips, and many parts.

I wrote a song about a pocket knife. This is a Gibson J-15.

 
I ended up re-gluing the saddle again and this time it's much closer to center. It's not exactly perfect, but it's down to a half millimeter difference this time. I think I should be able to live with that.

So I made a strange discovery about the tuners on this guitar. At this point I doubt anyone really cares, but I'm posting about it here anyway in case anyone searches for information about this sort of thing in the future.

As part of my tinkering process for learning purposes, I took out the tuners before I noticed that they weren't all the same height. The reason why this is strange is because this is an acoustic guitar with a 3x3 tuner arrangement (3 on the left for the bass strings and three on the right for the treble strings) on an angled headstock. Staggered tuners are typically only used with solid body (electric) guitars which have inline tuners (all in one row) on a straight headstock (parallel to the neck).

But it gets even weirder. The tuner heights are as follows:

1 tall
2 medium
2 short
1 shortest

Usually with staggered tuners you would have 6 different heights, with the tallest being at the front (low E or 6th string) and the shortest being at the back (high E or 1st string). In other words, each tuner gets shorter as you go from the front of the row from the thickest string to to the back of the row to the thinnest string. But that's not what I have.

So how am I supposed to arrange these tuners on my angled 3x3 headstock?

Quick recap:

acoustic steel string guitar

typical angled/tilted headstock

typical 3x3 tuner arrangement; bass tuners left side, trebble tuners right side

tuner heights are 1 tall, 2 medium, 2 short, 1 shortest

I should also add that I use a wound 3rd trebble string (it's coiled in wire like the 3 bass strings). This is actually an optional thing. You can get third treble strings which aren't wound.

There are ton of different ways to arrange these tuning pins.

This is what I settled on:

6th string - shortest
5th string - short
4th string - short
3rd string - tall
2nd string - medium
1st string - medium

This should slightly increase the break angle on the bass strings and slightly decrease it on the treble strings.

I would love for someone to yell at me and tell me how I'm an idiot and I'm doing it all wrong, because it would mean that I might learn something.

If my understanding is correct, I'll get better sounding bass and high strings which are easier to play. That's the theory, anyway. In practice... I don't know.

Since the headstock is angled already, I doubt that I am making much of a difference by arranging the tuners this way. When I finally string this thing up to play it, I imagine that I won't really notice anything, and I'm probably just spinning my wheels over nothing.

...but you definitely would not want to arrange the tuners like this with a headstock that isn't angled.

Seriously though... why did the manufacturer do this? It's even more baffling than the fact that they built the guitar with good fret spacing, but then for some reason they ended up putting the bridge in the wrong spot, which naturally resulted in the guitar being basically unplayable.

o_O
 
I finally strung it up with a brand new set of strings, and I think it sounds way better than a cheap guitar should.

There is one slight problem though. The low E is just a hair sharp, but it's right on the edge where I think some people probably wouldn't even notice it. I do notice it, so it bothers me. Thankfully, I believe it is an easy fix. Basically I think I just have to modify the saddle where the E string rests, which would turn it into a "compensated saddle". Compensated saddles are a pretty common thing on guitars, but usually it's done for the treble strings.

If anyone has any thoughts on this, let me know. I don't believe this has anything to do with the way I arranged the tuners (see the previous post for an explanation), but maybe I'm wrong. I don't know a whole lot about properly setting up a guitar. I'm still learning about that side of things. Usually I just like to play and not worry about all of the technical aspects.





edit: the issue appears to be with the action, or at least the action is where the underlying issue is showing.

I tuned the guitar down to D standard, and I noticed with the lower string tension, the 6th string was less sharp than before. Upon inspection of the action, the 6th string is noticeably higher than the 1st string. What that means is when I fret notes on the 6th string, the extra travel distance is causing the notes to play sharp, especially down towards the body of the guitar where the action is highest.

I should also note here that I discovered the 5th string is also slightly sharp, but it's a lot harder to notice.

Is the saddle shape to blame? Or is the neck warped? Or maybe the soundboard where the bridge is mounted is not straight? Or is the bridge itself poorly made? I don't know the answer yet.

Still, it's kind of interesting. This has been a fun learning experience. :)

Anyway, I think it's probably fixable. Even if the underlying cause turns out to be difficult or impossible to fix, then I think I can still at least modify the saddle to compensate for it so that I'll have good intonation on the affected strings.

edit2: So I talked to a guy at one of the local guitar shops, and he showed me that the bass strings being higher than the treble strings is actually normal. So I'm going to leave that alone. But looking at the action, it's definitely way too high, so what I am going to do first is lower the saddle and see if that fixes it. If anything, it should improve it. After that, if it is still a bit sharp on the low E, I'll see about compensating the saddle, and hopefully that should do the trick.

Learning is fun. :cool:



edit3: the problem mysteriously fixed itself. I don't know why, but I do have one or two ideas. But that's all they are. Just speculation. 🤷‍♂️

I'm going to ignore those theories and just assume that my guitar is haunted and that it healed itself. 👻🎸
 
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