Setting Intonation with compensated bridge?

**duffey is my hero** · Jun-22-2006, 12:27am

I play a michael Kelly Mandolin and it has what I believe is called a compensated bridge. I am trying to record and notice that the A and D string are out of tune when played up the neck. This also means that all of my chords are out of tune slightly. I set the intonation using guides online that say to move the bridge until both the E and G strings are in and this will take care of the two inner ones. But, my A string is sharp when played up the neck and my D string is flat. This seems to be because of my compensated bridge becuase the strings meet the bridge at a different place. I thought that a compensated bridge is suppose to mean better intonation but I can't get it right. If I get the A or D string on at the 12th fret and everywhere else, that means that the others are off. Can anyone give me some good advice. This is probably something I should already know having played the thing for 2 years.

JOshua Britt

www.thefarewelldrifters.com

**Antlurz** · Jun-22-2006, 12:39am

Off the shelf comp'd bridges are just an "average".

If you need to get closer, individual modification of the bridge likely will be necessary. Like on the A strings, the bridge would need to be cut to make the length slightly longer.

Another thing to realize is that a change in string guage or composition will likely also change the compensation you have now. It could go better or worse. the thing is, if you intend to change the string guage or composition, now is the time to do it, before you alter the bridge, since the intonation will likely be different after you change them.

Ron

**duffey is my hero** · Jun-22-2006, 12:53am

Is this cutting something that I could do myself easily? Also, How would I add more to the D string? I am in love with the strings I use now so a change is probably a bad idea. I use the J-74s D'addario. Thanks for the reply!

**mandroid** · Jun-22-2006, 1:31am

a Peterson Strobe tuner is a good tool to use for reference. about $250. minimize guessing that way.

**Antlurz** · Jun-22-2006, 2:23am

The different bridges offer different amounts of material to work with. Sometimes, it is necessary to start from the ground up to get it. Other options might be to cut out a section and add in a thicker block to work with. Every instance might present it's own challenges as to how to go about it. The actual change needed probably won't be a lot, as you can see by the existing bridge cuts. Maybe the D could be sharpened by gluing a small piece to the front edge....

In other words, "it depends"

Ron

**MarkG** · Jun-22-2006, 3:25am

You might just want to check that you don't have your bridge saddle on the wrong way round. This would have the effect of making the A strings intonate sharp and the D strings intonate flat as you describe above. It's an easy mistake to make.

-mark

**Antlurz** · Jun-22-2006, 4:45am

Good point. Should be easy enough to figger out. just look to see if the big strings are in the big grooves, and vice versa... unless maybe the original installation was backwards. Oops.

Ron

**hungry mountain boy** · Dec-10-2006, 2:43am

So how should the bridge look if not put on right in the first place. The saddle compensation, I'm speaking of?

**Antlurz** · Dec-10-2006, 3:24am

Just imagine turning it around 180 degrees. the D string positions foreward of the A string, and also would if you turned the bridge around backwards, but not exactly the same amounts.

Ron

**hungry mountain boy** · Dec-12-2006, 7:46am

I was told there are two kind of compensated saddles, the one I have the G and A parts are in the same position and
that is kind of back and then the D is forward and the A
is back. Does anyone know if that is how it is supposed to
be?

**Paul Hostetter** · Dec-14-2006, 2:45pm

I wish there was a hard and fast rule, but there never has been. Check this:

The top one, in purple, is the usual current bridge. It's usually put on with the treble strings coming over the left side on this sketch, the one point of contact that's set back a bit. IOW, it's not bilaterally symmetrical. But sometimes it's installed the other way around. Most people play them and never notice which is which.

The bottom one is another configuration that happened on earlier Gibsons, and is one I personally find works fairly often. It's bilaterally symmetrical: it doesn't matter which side is the treble or the bass, as long as the slots are cut right.

Before you get any more carried away with the bridge, please make sure the nut slots are really clean and correctly cut with the string contact right at the front edge, and not too high. Then check the bridge intonation, with fresh good strings. The various intonation formulas are really meant to (and usually do) work with medium strings on a normal 13-7/8" scale at normal pitch. I proceeed with that check by making sure the E is intonating 100% correctly, then go from there.

**hungry mountain boy** · Dec-15-2006, 7:41am

Thanks.

**Paul Hostetter** · Apr-16-2011, 11:29am

I just realized, as this post has been exhumed from five years ago, that my remark in post #11 about the treble vs bass is exactly backwards—oops! On the purple bridge the treble strings would be on the right, not the left. The rest of the post still makes sense.