ABG String Gauge and Intonation

topper · #1 08-20-2008, 08:01 AM

So I've heard if I change my string gauge I will need to re-check and reset my intonation.

Anyone know how this works exactly? If I go to a thicker set of strings which way will I need to adjust my intonation?

I know I could just change the strings and check, but here's the thing... I've got an acoustic bass I use to practice with at home. The intonation on it used to be fine, but I've noticed recently that it is off. Since it is acoustic, it doesn't have adjustable tail pieces. The bridge seems fine, nothing has come loose nor does anything appear to have tilted or shifted.

I changed strings a while back and didn't really pay attention to the gauge that was on it and what I replaced them with. I'm wondering if a simple change of string gauge could bring this back to a correct intonation.

XylemBassGuitar · #2 08-20-2008, 11:59 AM

Hi topper,

All things being equal, higher tension strings (the thicker ones) will require less compensation than low tension strings.

That is, the thicker strings should actually be better intonated with the saddle slightly farther forward (towards the neck) than with thinner (lighter gauge) strings.

Note: I am writing all of this under the assumption that you understand how to check and set intonation, which it sounds like you do.

Here are the physics:

The strings are streched more in the higher fret positions than in the lower positions. This extra stretch puts more tension on the string, effectively raising the frequency of the desired note. Higher tension (or thicker, in this case) strings are stretched less than lower tension strings, so they require less compensation (the saddles can be closer to the neck).

It is possible that a change in string gauges would correct your intonation. Several other factors could affect your intonation as well, but I'll touch on those in a second.

So, to determine which gauge to change to, find out if your intonation is flat or sharp.

If it's flat:
You should change to a lighter gauge. Heavier gauge strings require a saddle position that is closer to the neck. Since you can't move your saddle, it would be too far back for heavier gauge strings, effectively making the strings "longer" causing the higher notes to be flat.

If it's sharp:
You should change to a heavier gauge. Lighter gauge strings require a saddle that is farther back from the neck.

Of course, every instrument is different and there are always exceptions to the rule. It is also possible that your intonation is off for other reasons. Here are a few:

If you've raised your action since you bought the bass, a higher action will require more compensation than a lower action (because the saddle is higher, the string is stretched more, causing higher frequencies, requiring the saddle to be moved back from the neck).

If the body under the bridge is bowed up, that could affect your intonation.

Changes in humidity could change the sizes of various parts of the bass, throwing off your intonation (the changes in sizes are fairly small though, so this is more of a rare possibility).

A change in neck relief could effectively raise or lower your action, also possibly throwing off the intonation.

Try changing the string gauges first. If that doesn't help, do a setup (if you know how) or send it to a technician to do a setup.

Note: You will probably need to re-adjust your truss rod appropriately (again, if you know how) once you have changed string gauges.

Whew, sorry, this post reads like a novel. Let me know if you have more questions. If not, let me know how it turns out.

Good Luck!

topper · #3 08-20-2008, 10:10 PM

This was really helpful. It's midnight and the wife is sleeping in the bedroom where the bass is. I'll check to see if the intonation sharp or flat tomorrow evening and get back to you.

Many thanks!!

XylemBassGuitar · #4 08-21-2008, 09:18 AM

Glad to help! Let me know if it fixes the problem.

chizn · #5 08-21-2008, 09:23 AM

http://www.garywillis.com/pages/bass...tupmanual.html

is a pretty nice guide on how to setup your bass. a few basics anyway. theres a section on the intonation at the bottom. good luck setting up!

topper · #6 08-21-2008, 06:03 PM

Ok, the intonation is sharp. When I tune the bass then check the note at the twelfth fret it is noticeably sharp.

The effect is very pronounced on the E and A strings but much less so on the D and G.

I'll try some heavy gauge strings.

SGD Lutherie · #7 08-21-2008, 06:34 PM

Quote:

Originally Posted by topper

Ok, the intonation is sharp. When I tune the bass then check the note at the twelfth fret it is noticeably sharp.

The effect is very pronounced on the E and A strings but much less so on the D and G.

I'll try some heavy gauge strings.

Just move the saddle back.

Action has more of an affect on intonation than gauge or tension. You can have a thin string or a heavier string, but when they are tuned to the same pitch the tension is about the same.

The higher the string is, the more you have to stretch it down to the fret.

If the string is sharp at the 12th fret, simply adjust the bridge saddle farther away from the neck. If it is flat, move it closer to the neck.

This changes the length of the string. Just keep adjusting it, tune it back to pitch, and check the intonation. You should perform this test with the bass in playing position, not laying on it's back. That can deflect the neck.

Trying to adjust intonation by changing stings is a crap shoot.

topper · #8 08-22-2008, 06:01 AM

Quote:

Originally Posted by SGD Lutherie

Just move the saddle back.

Thanks, you must have missed that this is an acoustic bass without adjustable saddles.

SGD Lutherie · #9 08-22-2008, 09:56 AM

Quote:

Originally Posted by topper

Thanks, you must have missed that this is an acoustic bass without adjustable saddles.

I sure did!

You can have a compensated saddle made that can help a bit.

XylemBassGuitar · #10 08-22-2008, 11:23 AM

SGD is right about the height of the action. That will definitely make more of a difference in your intonation than string gauges.

But, it doesn't sound like your action was raised.

It is possible that the neck has gained some relief since you bought the bass, which could have the same effect as raising the action, causing the strings to go slightly sharp.

If the bass is really sharp, the string gauges might not make too much of a difference, but if you are only off by a handful of cents, they might do the trick.

At any rate, if the heavier gauge strings don't work, you could go definitely with SGD's suggestion for the compensated saddle.

Let us know how it turns out!

topper · #11 08-22-2008, 01:54 PM

Thanks all. The action on the bass is pretty high. It may have been getting progressively worse and I hadn't noticed. I kind of figured all acoustic basses might have really high action. This is the only one I've played.

This is a pretty cheap bass, so I'm not inclined to spend money on having a saddle made.

I think the first thing I may try is adjusting the neck relief. If that might improve the playability and the intonation, it sure seems worth trying. And it's free! (unless I break something)

Mastermold · #12 08-22-2008, 02:27 PM

Glad I found this thread -- I recently put new strings on my jazz fretless and the intonation went bad. When I get home later I'll have to pull this up and see if I can fix it.

Thanks for the advice gents!

XylemBassGuitar · #13 08-22-2008, 02:27 PM

Yeah, in my experience it's hard to find a good cheap acoustic bass guitar.

Like you said, adjusting the neck relief is a pretty good option at this point.

If you have a lot of relief near the higher frets, taking some out by adjusting the truss rod could definitely improve your intonation. You'll effectively be bringing the neck closer to the strings, decreasing the amount by which the strings will stretch when fretted. Since the intonation is sharp, this should help, at least a little.

Sorry, I'm repeating myself...

Note: Be really careful with that truss rod adjustment. If you don't have experience adjusting truss rods, you should probably talk to a professional before making any changes. A broken truss rod could make the bass completely useless.

I'm not assuming you don't know how to adjust the truss rod, I just want to make sure no one breaks their rod because of reading some forum thread.

Good Luck topper! Let us know if you need any more info.

XylemBassGuitar · #14 08-22-2008, 02:34 PM

Mastermold,

I'm assuming that your jazz fretless is an electric bass with movable saddles at the bridge.

If I'm correct in my assumption, don't worry about changing your string gauges to correct intonation. All you'll have to do if your string gauges change is adjust your saddles properly to correct the intonation on your bass.

I'm not sure if you noticed, but topper's bass is an acoustic, so he doesn't have movable saddles. Thus, some of this thread may not apply to your situation.

If you did notice all of this, sorry, nevermind me...

If you need advice on setting your saddles, give us a jingle...

Mushroo · #15 08-22-2008, 02:36 PM

Quote:

Originally Posted by Mastermold

Glad I found this thread -- I recently put new strings on my jazz fretless and the intonation went bad. When I get home later I'll have to pull this up and see if I can fix it.

Thanks for the advice gents!

I'd advise starting a new thread for your question, since fretless intonation is a different can 'o' worms... you might find some answers with a little searching as well.

Mastermold · #16 08-22-2008, 02:38 PM

Quote:

Originally Posted by Mushroo

I'd advise starting a new thread for your question, since fretless intonation is a different can 'o' worms... you might find some answers with a little searching as well.

Thanks, good idea. I'll start with the search feature since there's very little that hasn't been done to death around here!