Action, intonation, truss rod?

b1j · #1 07-31-2022, 05:52 PM

Today I played a Martin Special 16 at Guitar Center. This is the blingless wonder with 85% of the tone of an HD-28E at half the price.

I liked it, but I’m wondering if it could be set up better. Action was high at the 12th fret. I didn’t bring my gauge, but I’d guess 5mm or so. I checked intonation with my cents tuner. Each string was between 6 and 8 cents sharp when fretted at the 12th fret, compared with the first harmonic.

It seems to me that both action and intonation could be brought into line by changing the angle of the neck. (Pardon me for not looking up the correct terms before writing this.) I would want to bring the line of the frets up a couple of mm on the bridge (lower the headstock compared to the neck joint). There seems to be a good amount of “relief” (is that the right word?) in the neck — it’s slightly concave along the line of the frets.

Is a truss rod adjustment all this guitar needs? Of course you can’t say without seeing it, but in general, does the truss rod seem like a reasonable first place to look?

I’ll do some more reading and come back later. I’m going to read Basic Guitar Setup 101 by Charles Tauber.

Fathand · #2 07-31-2022, 06:55 PM

Before you look at resetting the neck angle, look at the bridge/saddle. Saddles can be removed and sanded on the bottom to lower action. Ideally they protrude from the bridge about 1/8"but can go down to maybe 3/32" but they shouldn't be that low on a new guitar.

Truss rods are not there to lower action, they are there to adjust neck relief.

When you measure action at the 12th fret, measure from top of fret to bottom of the 6th string. Most player prefer this to be less than 1/8th inch, 3mm.

If you otherwise like the guitar, tell the store to bring the action down to something you can live with. If they won't or can't, move on.

John Arnold · #3 07-31-2022, 08:38 PM

Neck relief is the first thing to adjust. Once the neck is straightened by tightening the truss rod, then you can reevaluate the action and decide whether a saddle adjustment will achieve the desired action. Minimum saddle height is around 3/32" above the surface of the bridge.

b1j · #4 07-31-2022, 09:23 PM

Thank you both for your advice so far. I've begun reading Charles Tauber's Setup 101 article, and I have determined a few things about the Special 16 I played today.

1) The relief on the Standard 16 in the store is clearly too concave. When I sight down my beautifully set-up 0-18 it looks nearly straight by comparison. Same with the J-45, which has received no adjustments after either the factory, or maybe Music Villa if they took to it before shipping. If I go back to the Special 16 I'll test it by depressing the first and 14th fret to see how bowed it is, and maybe bring my 24-inch straightedge. But there's no doubt it needs a truss rod tightening. Guitar Center said they'd do that for me before I decide to buy.

2) The action on the Special 16 is way too high. If I go back I'll bring my string-height gauge.

3) The string heights at the nut seem good. Again, I'll measure these, but the 1st-fret/2nd-fret test showed that the nut is an effective 0 fret for all six strings.

4) Height at the saddle is a question. There is over 1/8" of saddle above the bridge, so if it's too high there's room to lower it. But where will the line of strings point when the relief is adjusted?

I want to play barre chords with little effort. I want to be able to play Julia without squashing some of the notes. I can more or less do those things on my other guitars. Would this newcomer fit in with the rest of the group?

Can any guitar be very well set up so that it plays easily? Nagging at me is the question of whether a guitar at half the price of a Standard model, even a Martin, is built well enough to take a precise setup and play beautifully. My head says Probably but my heart wonders. Is the fretboard straight? The specs say the frets have been plekked, so that's encouraging.

Maybe I'm too worried. A professional luthier or repair person should be able to get any guitar into shape, right. (Right?)

Sasquatchian · #5 08-01-2022, 01:29 AM

Do as the master John Arnold suggests. The first thing to address is always neck relief. You can check that in the shop with a capo right on the first fret and then fretting at the 14th fret. Many people recommend between .003 and .007" relief in the middle of that range. My guitars with adjustable truss rods like to be on the short end of that but you might like something slightly different. Set that appropriately and it may fix all the other problems, or, at the very least, will point you to the next step. But don't forget that if you then need to still lower the action at the 12th fret, say by one millimeter, you will need to take two millimeters off the saddle. But first things first...

If you're in the store selling the guitar, they *should* be able to both check the neck relief and do the truss rod adjustment right there in front of you. You can literally do the whole thing in two minutes. At least start there.

b1j · #6 08-01-2022, 02:07 PM

Quote:

Originally Posted by Sasquatchian

Do as the master John Arnold suggests. The first thing to address is always neck relief. You can check that in the shop with a capo right on the first fret and then fretting at the 14th fret. Many people recommend between .003 and .007" relief in the middle of that range. My guitars with adjustable truss rods like to be on the short end of that but you might like something slightly different. Set that appropriately and it may fix all the other problems, or, at the very least, will point you to the next step. But don't forget that if you then need to still lower the action at the 12th fret, say by one millimeter, you will need to take two millimeters off the saddle. But first things first...

If you're in the store selling the guitar, they *should* be able to both check the neck relief and do the truss rod adjustment right there in front of you. You can literally do the whole thing in two minutes. At least start there.

Advice worthy of a Sasquatch. Thanks.

redir · #7 08-02-2022, 08:01 AM

It certainly is possible that too much relieve can cause bad intonation so as mentioned, start there. But to be very clear, setting the relieve with the truss rod does NOT change the neck angle. Only a neck reset will do that.

The truss rod does indeed affect the action on a guitar but only if the relief is not set properly. You don't want to 'adjust' the action with the truss rod but if the relief is way off one way or another than adjusting it to set it properly will have a 100% affect on the action.

In your case, with too much relief and high action chances are good that when you adjust the relief to the proper setting your action will go lower and hopefully be to your liking. And with lower action in this case with sharp notes your intonation will improve.

b1j · #8 08-02-2022, 11:08 AM

Quote:

Originally Posted by redir

It certainly is possible that too much relieve can cause bad intonation so as mentioned, start there. But to be very clear, setting the relieve with the truss rod does NOT change the neck angle. Only a neck reset will do that.

The truss rod does indeed affect the action on a guitar but only if the relief is not set properly. You don't want to 'adjust' the action with the truss rod but if the relief is way off one way or another than adjusting it to set it properly will have a 100% affect on the action.

In your case, with too much relief and high action chances are good that when you adjust the relief to the proper setting your action will go lower and hopefully be to your liking. And with lower action in this case with sharp notes your intonation will improve.

That is my hope. Visibly high relief and high action seem to be related.