Newbie intonation question.

[Lou Giordano]

My Kentucky KM-505 has gone sharp at the 12Th fret on G,D,&A (+10-15) on the tuner). I have not made any adjustments. The only thing I can think of is maybe the strings are getting old. I have J74s on for about 5 weeks with 1-2 hrs a day of practice on them. One of the guys that was trying it out at the Friday night jam noticed it. I am a new mandolin player so I don't need fresh strings unless the old strings are causing a problem. What do you think I should do?

Thanks

Lou

[billhay4]

Is it sharp on all strings? If so, look for a tilting bridge. Look anyway as this is a common issue. Tuning tends to pull the bridge over. It should be perfectly vertical to the strings.
Bill

[Lou Giordano]

Is it sharp on all strings? If so, look for a tilting bridge. Look anyway as this is a common issue. Tuning tends to pull the bridge over. It should be perfectly vertical to the strings.

Bill

What do you do about it if that is the case?

[Bill Snyder]

Pull it back straight.

[Lou Giordano]

Pull it back straight.

Well I said I was a newbie

I just pulled it back and viola, it's fixed.

Thanks

[Lou Giordano]

Follow up. I played it a little while and it went back the way it was. I this time I pulled back on the top of the bridge and placed my thumbs on the base of the bridge. It seems like the base moved forward and made a click sound like it popped in place. Now it is OK again. I hope it holds this time.

[chriss]

At the risk of re-stating the obvious- the bridge only RESTS on the top. It always finds a way to move around, tho only a little bit, with time. Who knows what- temp changes, tuning, ???, etc. The pressure from the strings isn't STRAIGHT down - the strings are angled down towards the tailpiece. So there's a "bias" -- or net force -- to move the bridge away from the tailpiece, towards the nut ... result = intonation goes sharp. You can loosen the "middle" 6 strings, leaving bottom G and top E at correct pitch, and check+correct intonation. This makes it MUCH easier to move the bridge, and move it by the small increments that get it sounding really sweet. But here's what I've taken to doing. ... FWIW...

I generally change my strings 3x/year (4 months)... playing maybe average of 1 hr/day. Normally I change 1 string at a time, so the bridge stays put. I'm not a luthier at all, but once a year, I take all 8 strings OFF, + clean + dust off the fingerboard, top, headstock, tuner posts, lubricating tuners, etc. This means the bridge comes off. I mark it's position with dry-erase, masking tape, etc before I loosen/remove the strings. When I re-string it, I put on the 2 "outside" strings only --- one G and one E. Then I check/correct the bridge position- I start where it WAS, but it's usually moved some. After I have it right, then I put the other 6 strings on.

It takes maybe an hour with all the cleaning etc. But it's SO nice to have everything cleaned, and the intonation corrected. It just sounds SO SWEET. Worth an hour to me. Makes it SO nice to play + hear! Dunno how it moves but it seems to. Just TWICE as pretty. I've fallen into doing this about 2 wks before Christmas, just as I'm starting to sit down and do all the beautiful Christmas music. I find myself really looking forward to it!

HAVE FUN!

[billhay4]

Lou,
For further information and so you know how to intonate the instrument, let me add this:
Any one string should sound the same note when fretted at the 12th fret as it does when open (not fretted), but an octave higher. This is how you check the intonation of an instrument. Strike a string (with your tuner on) and strike it again with the 12th fret.
Now, in reality, only the G and E strings will be exactly the same on most instruments, so focus on these.
Suppose they aren't the same? The bridge has moved or tilted.
If it hasn't tilted, it's probably moved. If the note on the 12th fret is sharp, the bridge has moved toward the nut. If flat, the opposite. It's a trial and error process, but fiddle with the bridge until the G and E are spot on. The others will be close.
Oh, I don't try to move the bridge with the strings tight. When doing the above, I loosed all but one G and one E and then do the adjustment.
If the bridge is tilted, I'd loosen them all a bit and then straighten the bridge. Tighten one outside string part way and then one on the opposite side. Move toward the middle and then repeat starting at the two outside strings. This will help keep the bridge from tilting again immediately.
If the bridge does insist on tilting, it may need refitting to the top. Go here for instruction. The whole Frets.com site is worth your time.
Hope this helps.
Bill

[Lou Giordano]

Lou,
For further information and so you know how to intonate the instrument, let me add this:
Any one string should sound the same note when fretted at the 12th fret as it does when open (not fretted), but an octave higher. This is how you check the intonation of an instrument. Strike a string (with your tuner on) and strike it again with the 12th fret.
Now, in reality, only the G and E strings will be exactly the same on most instruments, so focus on these.
Suppose they aren't the same? The bridge has moved or tilted.
If it hasn't tilted, it's probably moved. If the note on the 12th fret is sharp, the bridge has moved toward the nut. If flat, the opposite. It's a trial and error process, but fiddle with the bridge until the G and E are spot on. The others will be close.
Oh, I don't try to move the bridge with the strings tight. When doing the above, I loosed all but one G and one E and then do the adjustment.
If the bridge is tilted, I'd loosen them all a bit and then straighten the bridge. Tighten one outside string part way and then one on the opposite side. Move toward the middle and then repeat starting at the two outside strings. This will help keep the bridge from tilting again immediately.
If the bridge does insist on tilting, it may need refitting to the top. Go here for instruction. The whole Frets.com site is worth your time.
Hope this helps.
Bill

Thanks Bill

It has gone back again so I will follow your instructions. Like I was saying the base moved a bit but that is with the strings tight. I will loosen them and start over. It will be Sunday till I can get to it. I will post an update ASAP. I was thinking of doing the refit so the link will help if I have to go that far.

[Lou Giordano]

Saturday morning I went through the procedure of loosening all but the top G string and the bottom E string. Before I started I noticed that the bridge had moved to the right looking up from the end piece. I moved it left until the G & E strings seemed to be equally distanced from there edge of the fret board. Then I went to work on the intonation. It took just a little more patience then I thought I had, but I got it done.

It is holding this time. The D string is just a touch sharp and the A is 10-12 sharp at the 12th fret, but that is how it always was. I think it is time for a new tuner. I have the Intelli 500 tuner it is 1 year old and its acting a little weird even with a new battery.

Would a Cumberland Acoustic bridge hold better, or is this just the nature of the beast?

Thanks again for your help

Lou

[Phil Goodson]

Lou,

Good job! Sounds like you've got things figured out.

Just a thought: To split hairs, and getting to tiny tweaking decisions, I'd probably adjust the bridge so that the D & A strings were a little closer to perfect, at the expense of the G string.

There is some data to suggest that the human ear likes to hear low tones as slightly flat and high pitches as slightly sharp. There is a technique called "stretch tuning" that takes advantage of these tendencies.
When I set my intonation, I'd prefer the G be a little flat at the 12th fret rather than letting the D be sharp. Often, when you fret a note on the G string, you stretch the string a little more and inadvertently correct the flat intonation anyway.

I wouldn't start over just to do these tweaks, but if I had all the strings off in the future, I'd consider moving the bass end of the bridge slightly tailward.

Overall, good job!

[Lou Giordano]

Thanks Phil,

I'll do that on my next string change.

[billhay4]

Hey, Phil,
I didn't know that. Good information to have.
Bill

[Folkmusician.com]

Hi Lou,

While it is perfectly normal for a bridge to migrate around, and sometimes get a lean, it shouldn't do it on a regular basis.
When it leans, is just the saddle portion leaning, or the foot as well? Part of my setup routine is to check the posts in the bridge. It is very common for them to not be threaded in far enough, allowing them to lean.

Would a Cumberland Acoustic bridge hold better, or is this just the nature of the beast?

It is nearly impossible to keep your intonation spot on. Strings stretching, humidity and temperature will all take their toll. These might be noticible, but shouldn't be severe. Not to the point where you would need to move your bridge often.
You mentioned playing 5 weeks at an average of 1:30 hours per day. Now 52 hours of play is more than enough to ruin a set of strings and set off intonation issues. That is some serious play time on a single set of strings (it does not sound like this is your main problem).

Also, remember to do the final intonation adjustments with the instrument in the playing position. You can do basic adjustments with the instrument laying down, then tweak in the playing position. This can make a noticible difference. Lastly, your average tuner such as the Intelli, is not accurate enough to get the intonation spot on. These are great tuners, but you need a strobe tuner or electronic equivalent for intonation. With your Intelli, you can get it "pretty close".

A CA bridge tends to have better compensation and is a vastly superior bridge. Even if there is no problem with your current bridge, the CA would be a nice upgrade and if it is fit well, you should get better tone as well. Of course it is probably not needed just to fix your intonation issue.

[Lou Giordano]

Thanks for your help Robert.

I want to make it clear, I am not obsessing over the intonation. It was pointed out to me that it was off by someone who would know.
I am so new I would not notice a change with my newbie skills. It did make me curious though.

I will change my strings shortly. I will put the CA bridge on my wish list, but paying for the bridge and paying to have it fitted and set up is not something I will be able to do for a while.

Last adjustment in the playing possition, another good tip.

Lou

[Lou Giordano]

I put new strings on this past Thursday (J74s). I got the G string -5 flat and the rest were right on. I played it a lot on Friday, about 3hrs of bluegrass strumming with some friends and I practiced my usual amount over the week end. The bridge has moved again, back to where it was when I first posted. I guess that means a refit. This is frustrating. Maybe it's my newbie strumming.

[billhay4]

If it keeps moving like that, I'd guess there's something wrong with the bridge itself. It could be lose posts. It could be a poor fit to the top by the bridge base.
Do you have to re-tune this instrument a lot?
Bill

[Lou Giordano]

Yes I do have to re-tune it a lot. The first G string and the A strings mostly.

The bridge seams to be as low as it can go. I don't think it is leaning.