Flat 12th fret harmonic

pbass2 · #1 10-25-2009, 09:52 AM

I'm picking this up from my other thread, just to simplify as now I have this one question: on my 4 string MM Stingray, stock, no mods, I'm guessing about 2-3 years old, I have this issue: Across all four strings, the harmonic at the 12th fret is a teeny bit flat compared to the open strings. I'm using a decent tuner (Turbo Tuner), powered by AC, new battery in the bass. I just put on new DR Lo-Riders. I discovered this after changing strings on this new-to-me bass and started trying to finesse the intonation. I understand it could be bad strings--just seems really unlikely given that it's the same on all four strings but I know anything's possible. I'm giving up and will take this to a pro to set-up this week(and bring yet another set of new strings just in case), but what other possible reasons are there that this would be happening? My understanding is that even if the neck had a crazy bow in it, and the saddles were all in whacky positions even that wouldn't matter. The open string and the 12th fret harmonic should be dead-on, yes?

santucci218 · #2 10-25-2009, 09:54 AM

tune to the right pitch with the harmonics, then intonate it with new strings.

pbass2 · #3 10-25-2009, 10:02 AM

Yeah, but in theory at least, shouldn't the open string and it's 12th fret harmonic be in tune with one another? I expect there's some chance for "wavering" as the overtones hitting the tuner are different, but this is consistently off on all four strings.

santucci218 · #4 10-25-2009, 02:07 PM

i guess in theory. this is just the way i have done it. I tune with my harmonics every single time, than intonate by playing the 12th fret. thats just how its done.

ByF · #5 10-25-2009, 02:11 PM

How flat is it? How many cents? Is anybody going to hear it? If nobody can hear it, don't worry about it.

Ed

()smoke() · #6 10-25-2009, 02:19 PM

yes, the octave harmonic should be one octave higher than the open string by definition, right?

can you intonate the instrument correctly using the open and 12th fretted notes?

pbass2 · #7 10-25-2009, 02:28 PM

Quote:

Originally Posted by ()smoke()

yes, the octave harmonic should be one octave higher than the open string by definition, right?

can you intonate the instrument correctly using the open and 12th fretted notes?

That's what I thought, just due to physics(and of course, if you weren't plucking the harmonic at the right spot you wouldn't get the clear ringing harmonic outta the string, ruling out that factor).

I have NOT gotten the bass intonated properly yet, but pretty close, using the 12th fret harmonic/fretted 12th fret approach. If I kept cranking the saddles inward I believe I would get it there(almost running out of screw though on a couple).
But as I say, the harmonics are flat compared to the open strings--by a little, which just had me pause the process in my tracks. Hard to say how many cents as the Turbo Tuner doesn't show that. Here's what I just discovered--I started backing the saddle on the E string back out and indeed the harmonic got closer to the pitch of the open string. If I kept going I can see I would get it right on. But now the fretted 12th fret is REALLY flat compared to the 12th fret harmonic!
Oy.

BuffaloBass · #8 10-26-2009, 08:18 AM

Got a sweep on that tuner? Put your OLD strings on. Move the saddle in the direction you want the needle to move. Shortening to raise pitch, lengthening to lower pitch. Then install the new strings and check. Why? Well, I'm just a hobbyist, and it can take a few saddle repositionings to get it right. Think of the "damage" that does to the strings.

I use an el cheapo Korg for this and finalize with ear, but the Korg is still better than my ear. The B string, due to thickness I believe, is a compromise between 12 th fret vibrations and and lower register vibrations.

Also must be careful about how exactly you "fret" that 12th note.

It'd be a cinch with one of those fancy strobe tuners.

202dy · #9 10-26-2009, 08:32 AM

Here is another thought.

Over time the the saddles can get grooves worn in them from the string wraps. If you look at the seat you will see some grooves running east-west parallel with the saddle. When moving the saddle the string will find the grooves and settle in. This causes the saddle movement to be fixed "leaps" instead of moving the intonation smoothly through the continuum.

The remedy is to smooth the grooves with a round file. Gauged nut files are the perfect tool for this repair.

KJung · #10 10-26-2009, 08:45 AM

Interesting. I don't see how this can even physically happen. Not sure what is going on. It would have nothing to do with 'intonation' or bridge saddles or anything, since that stuff would equally impact the open string and the harmonic.

I can't think of how this can even physically happen?

Here's one thing to make sure of... the attack of the note will be different (most likely) when you pluck the open string versys the harmonic. It would not surprise me if one or the other was 'out of tune' at the initial attack. However, within a couple of seconds, the notes should come together.

Subscribed... since this seems very strange.

dystopiate · #11 10-26-2009, 08:53 AM

I'm with KJung. It seems most likely that you're attacking the open string harder than the harmonic. Most of the other suggestions have to do with fretted intonation, but you're having problems with open vs. 12th fret harmonic. Just seems really weird to me.

MonetBass · #12 10-26-2009, 08:54 AM

Quote:

Originally Posted by KJung

Interesting. I don't see how this can even physically happen. Not sure what is going on. It would have nothing to do with 'intonation' or bridge saddles or anything, since that stuff would equally impact the open string and the harmonic.

I can't think of how this can even physically happen?

Here's one thing to make sure of... the attack of the note will be different (most likely) when you pluck the open string versys the harmonic. It would not surprise me if one or the other was 'out of tune' at the initial attack. However, within a couple of seconds, the notes should come together.

Subscribed... since this seems very strange.

This is what I was thinking. It is impossible for a harmonic to be out of tune with the open string since it is based on the fundamental of the open string. Moving the bridge saddles will not change that.

And KJung's point of how you're attacking the open string makes sense. When tuning the open string, make sure you let it 'settle' before tuning it. And use a lighter touch.

the yeti · #13 10-26-2009, 08:57 AM

202dy · #14 10-26-2009, 09:07 AM

Quote:

Originally Posted by KJung

Interesting. I don't see how this can even physically happen. Not sure what is going on. It would have nothing to do with 'intonation' or bridge saddles or anything, since that stuff would equally impact the open string and the harmonic.

I can't think of how this can even physically happen?

Pretty simple, really. The vibrating string, which is typically steel and/or nickel is harder than the saddle material and abrades the seat in the saddle. Seen it many times in the shop on both guitars and bass guitars. Quickly smoothed with a file, setting the intonation is a breeze.

As far as the affect on the open string and the harmonic goes, it is not the same. The open string is tuned to pitch. The harmonic is not. As the saddle moves the string rides up and down on the peaks and in the valleys. The tendency when adjusting the bridge is to allow it to "click" into place in a valley. Coarse, sloppy threads matches make it almost a guaruntee that the string will seek the lowest point. Even when it is allowed to ride somewhere on the slope or peak abnormal wavering is typical. Remember, setting the intonation is a game of thousanths.

**Mulebagger** · #15 10-26-2009, 09:09 AM

Are you thinking that the 12th fret may be in slightly the wrong position?

Never had something like this happen. With a good set of strings, you should be able to intonate it properly, unless the 12th fret is the cause of your problem. Just my 2 cents.

202dy · #16 10-26-2009, 09:16 AM

Highly unlikely. Modern computer run machinery pretty much negates that possibility.

If the twelfth fret is suspect it would be from string wear. The string would no longer be stopped at TDC over the fret slot. That condition would also make it impossible to set the intonation. The remedy for this is a fret dressing.

LaklandBass · #17 10-26-2009, 09:17 AM

Intonation should be as simple as adjusting the fore/aft of your bridge saddle. Get a good tuner and tune the open string perfectly. Then check the 12th fret harmonic. If theyre off you need to adjust the fore/aft of the bridge saddle. Im pretty sure moving it back will take you sharper so try that. After each try you need to retune the open string perfectly and then check the octave.
Im not a pro with setups but this has always worked for me.

lbwdog · #18 10-26-2009, 09:22 AM

The way I'm reading this is, the actual harmonic (not the fretted note) is flat. I don't see how this could be! The bridge saddle wouldn't affect anything. The harmonic should be a perfect octave up from the open note.

If the pickup is too close to the strings, this could cause some strange overtones that could be out of tune with the open note.
Or possibly, a bad string might cause this, but unlikely all four!

Other than that, a defective tuner may be giving an incorrect read.

dmusic148 · #19 10-26-2009, 09:24 AM

Quote:

Originally Posted by 202dy

As far as the affect on the open string and the harmonic goes, it is not the same. The open string is tuned to pitch. The harmonic is not.

Pardon? This doesn't make sense. If the saddle is grooved, causing this 'clicking into place' issue you talk about, it would affect the open string and 12th fret harmonic equally.
Ken nailed it. When you pluck an open string, it will always go sharp for a moment. Sometimes very little, sometimes a lot, depending on attack. Pluck gently.
Also, turn your onboard Tone controls to the darkest setting- this masks overtones that tend to 'fool' tuners.

KJung · #20 10-26-2009, 09:28 AM

Quote:

Originally Posted by 202dy

Pretty simple, really. The vibrating string, which is typically steel and/or nickel is harder than the saddle material and abrades the seat in the saddle. Seen it many times in the shop on both guitars and bass guitars. Quickly smoothed with a file, setting the intonation is a breeze.

As far as the affect on the open string and the harmonic goes, it is not the same. The open string is tuned to pitch. The harmonic is not. As the saddle moves the string rides up and down on the peaks and in the valleys. The tendency when adjusting the bridge is to allow it to "click" into place in a valley. Coarse, sloppy threads matches make it almost a guaruntee that the string will seek the lowest point. Even when it is allowed to ride somewhere on the slope or peak abnormal wavering is typical. Remember, setting the intonation is a game of thousanths.

You, and most others on this thread are not understanding the OP. It's not the 12th fret NOTE that is not matching up with the open string, it is the 12th fret harmonic, that has nothing to do with intonation or the placement of the 12th fret. By definition, the open string and the 12th fret HARMONIC (which will only 'sound' in the correct place... regardless of where the 12th fret is) will be identical, and any bridge or nut adjustments (unless there is something I really don't know about) will impact the open and 12th fret harmonic identically.

This is not an intonation issue. My guess is, again, it is an attack issue (and per the above post) possible an overtone issue, given the uber precise spec's of the Sonic tuner.