Bass guitar to back up mandolin

[ald]

For anyone who knows somenthing about acoustic bass guitars: I bought a cheap acoustic bass to back up my mandolin on home recordings I am making. The sound is quite nice but the action is a bit high. One inch at the 12th fret. The height at the nut end seems to be perfectly OK. Dare I risk sandpapering the bridge or would this affectt the nut end as well? I definitely would not dare messing about with the truss rod.

[Jim]

I think you need both bridge and truss rod adjustments, 1 inch at 12th fret is way too high. What kind of Bass is it? Yes you can sand down the saddle and I would tighten the truss rod until the E string lays almost flat against the frets when fretted on the first fret and held against the fret where the neck joins the body. When you do that you should only be able to slide a playing card or maybe a guitar pick between the string and fret at about the 7th or 9th. This is a very rough estimate of how to set neck relief.The saddle I would sand until you had about 3/16th of an inch action height at the 12th fret. You can take it down till it buzzes and add shims til it doesn't but I don't think it would buzz at 3/16ths. I'm not at home so I can't measure my Bass action maybe someone else can give you a measurement of theirs. Seriously 1 inch at the 12 fret sounds broken and I'd look to see if the neck was firmly attached to the body.

[multidon]

Yes Jim beat me to it but his advice is spot on. There is something seriously wrong here. An inch is ridiculously high. If you have determined there are no construction issues like a failed neck joint or a lifting bridge then you have to start with the truss rod. Find the right size wrench and loosen it first. You are unlikely to damage anything by loosening. Then use a straight edge to see what you have. Then tighten the rod until it is just barely snug and measure again. You want just a business card worth of relief at the 7th fret. Once relief is set then do the action. When you sand the bottom of the bridge saddle you have to make sure you are holding it perfectly square in all direction. Take care not to mess with the position of the under saddle pick up if there is one.

I like the action a tad higher on an acoustic bass guitar than on an electric. I think Jim has it about right at 3/16. But your problem is there is no way that a simple set up procedure is going to lower your action enough when it's 13/16 of an inch too high. It won't even get you to the ballpark. I would be looking for some sort of structural issue.

[Billbass1]

Serious problem, YES ! If it really is one inch.
Are you sure it is an inch and not something metric ?

[ald]

Sorry about the panic, I was using my wife's metric ruler. Found a inch tape measure and it is just under half an inch, so it is still higher than your recommended 3/16. I thought an acoustic bass had to have a higher action than an electric one to compensate for the heavier playing/vibrations? So if I sandpaper the bridge, will it affect the nut end as that seems about right to me? I don't think I would like to mess about with the truss rod. What would you use as shimmying material?

[ald]

I see you are talking about sandpapering the saddle, not the bridge. I would not mind having a go at the bridge but the saddle...

[multidon]

The half inch is still way too high by about a quarter inch. I still think there may be a structural issue and I doubt a bridge adjustment will be enough.

I do not understand your reluctance to adjust the truss rod. Are you familiar with instrument set up procedures? The rule of thumb is you always set the neck relief first, THEN the action. There really isn't anything to be afraid of as long as you start by loosening first. Then as long as you tighten in small increments of an eighth of a rotation at a time you should be fine. You should not have to go much beyond a full rotation past just snug. At that point your rod is already doing all that it can.

I also don't understand your reluctance to sand the bottom of the saddle. This is the usual way that action is adjusted on this type of instrument, unless you do not have the traditional Martin type pin bridge glued to the top. This is the only type of bridge I have ever seen on acoustic bass guitars. The saddle should come right out of the slot and it will be easy to sand the bottom. What good would adjusting the bridge itself do? It is the saddle that affects the action. The only thing I can figure out is that maybe you have a floating bridge? I've never seen one on a bass guitar but I suppose it's possible.

If your nut action is correct as you claim lowering the action at the bridge should not affect it in the least. I would not worry about shimming the nut until such time it becomes a problem.

I do think the acoustic bass guitar needs to be a little higher than an electric but certainly not 1/4 of an inch higher!

[Billbass1]

Your bridge saddle may have removable shims under it . Check that first .
It's much easier removing shims than sanding the saddle .

[ald]

Thanks a lot for replying, Don. I have just looked at a drawing and I see know I have been confusing the terms. I always thought that the white part was the bridge (like the adjustable bridge on my mandolin and a bridge on violin) so when you referrred to saddle I thought you meant the wooden part into which the "saddle" is inserted. I don't mind sandpapering the saddle then but the thought occurs that their might be a pickup underneath (I plug the guitar into a computer for recording purposes). Sanding might affect the pickup! Maybe I should purchase a blank saddle to adjust and retain the original in case I make matters worse.

[Nevin]

Bass player here. Half an inch at the 12th fret is very high even for an acoustic bass guitar. You do not adjust the action with a truss rod. You adjust the relief (i.e the degree of bow in the neck). Relief does have some impact on the action but you have to check the relief before you adjust it. For minor hight adjustments, you can sand the saddle. Still you may have more of a problem than you can fix that way. I am concerned that you may have a neck joint problem or the neck may have been set at the wrong angle from the start. Either start reading up on how to set up your bass (frets.com is a great resource) or take it to a competant repair person.

Most acoustic bass guitar bridges are glued on, unlike mandolin bridges. If this is the case, sanding the briddge is probably the last thing I would try. If it is a floating bridge you could get some help there but still taking a 1/4" or so off a bridge is a lot.

[multidon]

Bill bass1 is correct. There may be removable shims under the saddle that you can take out. Sanding the saddle will not affect the electronics. The under saddle pickup will be sitting in the slot under the saddle. Don't make the mistake of confusing it with a shim! Shims will come right out. The under saddle pickup will be connected to a wire. It is not necessary to buy a blank saddle. You are overthinking this.

Judging by your posts you do not strike me as being very familiar with instrument repair. I would urge to to take it to someone who is. I still believe based on your description there is a problem here that sanding will not solve.

[ald]

OK, well thanks very much for all your replies and advice (and patience). No I am not very familiar with instrument repair but I can use sandpaper, so I was hoping it might be as simple as that.

[ald]

Thanks once again for all your advice.

Sorry to harp on about the subject. After your warnings, I was preparing to wend my way into town to get somebody to do the job for me then found this video clip which has almost the exact same bass guitar as mine (same colour, same truss rod position and even the same string height). Looking at how this bloke makes the adjustment (and yes an allen key did come with the guitar) I can't see anything going wrong!!! Unless you experts can see anything amiss? Should I go ahead?

http://www.youtube.com/watch?v=iiBMdV1uuuw

I should add that there is a mandolin component to this because I have stolen the bass accompaniement from the Lovin' Spoonful's version of Sportin' life to back me singing and playing the tune on mandolin (when I go up the neck on the bass for the higher part it becomes qute uncomfortable for my fingers)

[eadg145]

I, too, am a bass player, and I'm with Nevin on this one. If it's as you describe, you may have a more serious structural problem with your instrument. If you think the issue really is neck relief, then by all means try the (reversible!) adjustments. However, before you begin sanding material away forever, I strongly recommend you have a qualified luthier look at it.

[EdHanrahan]

... can see anything amiss?

Yeah, a few out-of-whack details:

1- Measure the relief between the 1st fret and the "body-joint" fret, around 14 on his bass, because the trussrod has no effect on the frets over the body and little effect on the frets over the heel of the neck. (The body-joint area often gets uneven frets, but that's not a trussrod issue).

2- As others have said above, loosen the nut before you tighten it. Some nuts do not move at all, and you need to prove to yourself that it WILL move before putting it under additional stress. Folks HAVE broken trussrods that way. Granted, that's mostly on older instruments, but why tempt fate? (If it's REALLY stiff, best to take the nut out and lubricate - mildly! Don't squirt oil in on the rod, you'll mostly make mushy wood, and maybe ruin the ability to adjust the rod at all.)

3- Speaking of additional stress: Do loosen the STRINGS before tightening the rod. His move straightens the neck WHILE raising the pitch of the strings. That's A LOT of added stress. De-tune by maybe 5 frets, adjust, then re-tune.

4- To actually move the nut by "1/4 turn", you'd have to loosen the strings for clearance anyway. Fortunately, his demo goes just short of 45 degrees, which would be 1/8 of a turn.

In rare cases, the nut may bottom out on the rod's threads, and you'll need to add a washer or three make the full adjustment. But, again, you can only know that the nut is bottomed by loosening it first.

[ald]

This are some tremendously good pieces of advice. It is a fairly new instrument but as you say why tempt fate. Should I mark it somewhere to show my starting point? Not really sure where!

[EdHanrahan]

... Should I mark it somewhere to show my starting point? ...

If you mean mark the trussrod nut at some point of its rotation that you might return to later, I never have. They're often hard enough to see at all!

Think of the neck straightness / amount of relief as a balancing act between the strings pulling the neck forward and the trussrod pulling it back. And that the trussrod itself is, IMHO, subject to some small amount of twisting when adjusted, especially under pressure. Just because you might get back to your mark at "12 o'clock" doesn't necessarily mean that the rod itself isn't twisted by bit, or maybe shifted at its anchoring point, thus giving more or less relief than you started with. I tend to let the relief measurement govern, dictating wherever the nut ends up.

Two add'l thoughts:
- Loosening a trussrod under tension is not near as risky as tightening one, IF you're sure that it does, in fact, turn smoothly.
- Modern "2-way" trussrods are a different animal, and don't depend so much on string tension to pull the neck forward - the rod can do that all on its own. But I still wouldn't adjust one under tension until I was sure that the nut is moving smoothly.
(And, uhmm, they might not even be made for bass guitars?)

[multidon]

Yes, they make 2 way rods for bass necks. My wife has a Carvin bass with a 2 way rod. It's needed too. The neck is dead straight and the string tension doesn't put enough relief in so we have to add relief with the truss rod.

[Barry Wilson]

I followed the directions at frets.com and just did the truss rod on an acoustic guitar for a friend. it was bought used and was out. I had always shied away from truss rod adjustments... it is a lot easier than I though to do.

[ald]

Sorry I am late getting back to you (been busy with work) but to conclude the story about my bass, I wound down the strings on the instrument and prepared to do battle. I inserted the key and tried to turn it anti-clockwise first as you all recommended but found it was impossible to move. I could have used more force but was afraid of doing any damage. I phoned a luthier in Brussels and he said he should be able to do it on the spot. So I will go along next week and take careful note of all he does so I will know for the next time.


Thanks once again for all your advice, which I have found very elucidating. I went to see a neighbour yesterday, who, I remembered, tinkers about with guitars. He showed me a guitar where he had tried to alter the truss rod. It produced a fracture in the wood where the fingerboard meets the neck and did not alter the relief one iota. I told him all your pieces of advice about loosening the strings, anti-clockwise first and then proceeding by degrees, the very opposite of what he did. So you all warned me very correctly. Thanks.

[ald]

I got my bass guitar back from the lauthier today. One hundred percent improvement. It is now almost as easy to play as my acoustic guitar. He charge me a very reasonable rate for the job. I also took in a cheap Ibanez mandolin I bought to take on holiday this year as a "beater". It was playable but sounded awful after the 5th fret. Now it is almost as easy to play as my Gibson. The sound is obviously not comparable with the G. but it is quite pleasant to play the instrument. I was expecting a bit of an improvement but my lauthier worked miracles. He took so much trouble with instruments, even though he sniffed at them a bit when he first saw them. He pretended to be Robin Hood firing arrows with my bass, so high and bowed was the action.

[Nevin]

Glad you got that resolved.