Intonation frustration

pbass2 · #1 10-23-2009, 02:38 PM

Normally, I have all my basses setup by a pro, but times is tough, and I'm endeavoring to make small adjustments myself these days.
I've got this newly acquired MM Stingray 4 string here--great bass. Came setup very close to how I like it as far as action, etc. Checked out the intonation and it was close, but needs a tweak)12th fret a bit flat. So, I put my strings on (DR Lo-Riders). I wanted the action a tad lower. So I experimented with the truss rod wheel setting to remove a smidge of relief (and I mean, I think I turned it 1/8 turn or less. OK, good, no fret buzz, etc.
On to the intonation---I cannot for the life of me get the A and D string intonated so that the 12th fret is not flat (I'm using a strobe tuner BTW).
Even as I crank on it to adjust it, the change is so minimal, that I can tell I'll run out of play in the saddle screws well before I get it into intonation. Any advice? Thanks.

dmusic148 · #2 10-23-2009, 02:40 PM

You are loosening the screws, right? So that the saddles extend, shortening the string? If that doesn't do it, the strings are defective.

pbass2 · #3 10-23-2009, 02:59 PM

Yeah, loosening. I mean it IS having an effect, but on the A string for example I'm gonna run out of screw before it gets intonated!
These are brand-new DR Lo-Riders (not to say I couldn't have a bad string or two). I have another used set I can try for comparison.

202dy · #4 10-23-2009, 03:21 PM

The first thing to do is make sure there is a good witness point in the string when tuned to pitch. Push down on the string so that it lies flat in both the saddle and nut seats. Then check the intonation again.

If that doesn't do the trick then the problem is at the nut.

Most often when the saddle travel is not enough to intonate the string the problem is at the nut. It is imperative that the nut slot forms a flat seat for the string so that it breaks at the bridge end of the nut. If there is a hump in the bottom of the slot it effectively changes the scale length of the string.

Take a pencil and coat the bottom of the slot. Tighten and loosen the string a few times then lift the string out of the slot. This will show where the string stops in the nut. Then recut the nut slot so that it is flat.

pbass2 · #5 10-23-2009, 03:30 PM

Very interesting . . . will check this out . .

dmusic148 · #6 10-23-2009, 03:37 PM

Quote:

Originally Posted by 202dy

If there is a hump in the bottom of the slot it effectively changes the scale length of the string.

If that was his problem, the fretted octave would be sharp, not flat.

202dy · #7 10-23-2009, 04:18 PM

Quote:

Originally Posted by dmusic148

If that was his problem, the fretted octave would be sharp, not flat.

Respectfully disagree.

pbass2 has not stated that the intonation problem is either sharp or flat. So the point is moot.

Assuming that the saddle seat has no abnormalities and that the string height is not extreme, if the saddle travel is insufficient to correct the intonation the problem lies at the nut.

The only other answer is that the bridge is not located properly. This is an unlikely proposition in an instrument manufactured on CNC machinery.

pbass2 · #8 10-23-2009, 07:22 PM

Quote:

Originally Posted by 202dy

Respectfully disagree.
pbass2 has not stated that the intonation problem is either sharp or flat. So the point is moot.

Assuming that the saddle seat has no abnormalities and that the string height is not extreme, if the saddle travel is insufficient to correct the intonation the problem lies at the nut.

The only other answer is that the bridge is not located properly. This is an unlikely proposition in an instrument manufactured on CNC machinery.

Thanks for all the info everybody. I had to put it aside but will get back at it tonight to see what I can suss out.
I mention that I cannot get it so the 12th fret isn't a bit flat compared to the open string and the harmonic on the 12th fret.--that's the issue I'm having. One thing I noticed, and it's ever so slight, is that the 12th fret harmonic is a TEENY bit flat compared to the open string. BTW, when I mention I'm using a strobe tuner, what it is is a Sonic Research Turbo Tuner--powered with AC, new battery in the bass, etc.
The saddle height is "normal"--nothing extreme.

202dy · #9 10-23-2009, 07:43 PM

You're right. You did post that. My apologies.

Check the saddle seat, too.

pbass2 · #10 10-23-2009, 07:57 PM

Quote:

Originally Posted by 202dy

You're right. You did post that. My apologies.

Check the saddle seat, too.

Of course--no worries--I appreciate the discussion. I just messed with it more--I got it CLOSER but the A and D saddle screws are not protruding from the saddle at all now--the ends being prolly about halfway inside the saddle. Is the saddle height a factor for this issue as well?
I'm also just wondering, since the 12th fret harmonic on all 4 strings reads as a tad flat compared the open strings, if there's something else at play, and, realistically, can it be perfect dead-on anyway, and lastly, maybe my tuner isn't going to be as precise as the standard big Peterson Strobe a real setup guy uses (even though my Turbo is supposed to be pretty good)?

MutronIII · #11 10-23-2009, 08:04 PM

Make sure the head of the screw is flush with back 'wall' of the bridge. If you are cranking the screw while the strings are under tension, rather than moving the saddle forward, the screw may be pushing out. When adjusting my MM bridge, I've found that you either need to put some slack on the strings, or put pressure on the screw to ensure that is doesn't pull back...

Saddle height is a factor. Simple trig, if the saddle (opposite side) is higher, the string length (hypotenuse) will be higher.

As far as the harmonic being slightly flat, I'd take that as a sign the string isn't tuned. The node at 1/2 string length should be exactly an octave up from the total string vibration. Could be a bum string...

Charles Fields · #12 10-23-2009, 08:25 PM

Yeah make sure you are pushing the screw's in all the way ,look at the back of the bridge and make sure their not sticking out,and try setting your intonation by hitting the otave harmonic first then the fretted note itself at the 12th fret that the problem i have never got a bad string ,but i guess anything is possible.

pbass2 · #13 10-23-2009, 11:35 PM

Well, loosening the strings BEFORE making the saddle screw adjustment has made a difference. I am now much closer to everything being hunky dory. I can get the 12th fret harmonic and the fretted 12th fret pretty much dead-on(at least on this tuner, which I can only assume is pretty accurate). Still, and this is across all four strings---the 12th fret harmonic is a teeny bit flat compared to the open strings. I can't say really how many cents with this tuner. In the process of adjusting all this, I starting getting some buzz down around the 4th fret, so I gave the neck a tad more relief, and now I'm back to adjusting the intonation again. Oy. Maybe I will just spring for a trip to my set-up guy after all, just to start off on the right foot before I go tweaking this bass too far.

mech · #14 10-24-2009, 06:53 AM

Be sure you are using the same finger pressure you play with. Using light finger pressure when setting intonation will cause the instrument to be sharp if your normal playing style is heavier. Pressing the string down between the frets will pull it sharp.