Bridge prependicular, square? Intonation bad.

[levin4now]

I've had my mandolin for about 3.5 years I think. After two years, I finally had the nut replaced (bone), and had the feet of my bridge fitted to the shape of the mandolin, (a thorough setup if you will). Well, I noticed that after I got it back that the intonation was off (worse than before). I should have brought it back, but it was a 2.5 hour drive to where I had it done and I lived with it. I couldn't stand it any longer. Even as simply as I play, if I tried to play the A note at the 7th fret on the Dstring along with the open A string, they clashed. (even if they were in tune when open).

So, I finally tried to set the intonation by trial and error tonight. I seem to have got it pretty good. I loosened all the strings, moved the bridge toward the nut (which ended up being wrong) and then tried it by moving it back towards the tailpiece. I only tightened up a Gstring partially to see if I was headed in teh right direction.

Well, I found that if the G string intonation was correct, and the bridege was square, or perpendicular to the strings, the intonation at the E string was still off bad. So, now my bridge is sitting at an angle to the strings and everyting seems pretty good.

Does anyone else have this? My mandolin is a pac-rim model.


Alan

PS After fine-tuning my tuning, I find everything is still not perfect with my intonation, but significantly better than before (bridge in cock-eyed mode.)

[Michael Lewis]

Alan, you did what you are supposed to do. Set the G so it sounds right, then set the e so it sounds right. You do this by hitting the harmonic at the 12th fret, then the fretted 12th fret, and they should sound the same.

The fact that your bridge is sitting at a jaunty angle is part of the beauty of the movable bridge design in that it allows the intonation to be set. Are you going to play the instrument, or look at it?

[AlanN]

oof-fah http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif

[Tim]

The fact that your bridge is sitting at a jaunty angle is part of the beauty of the movable bridge design in that it allows the intonation to be set. #Are you going to play the instrument, or look at it?
IF a setup was recently done that involve fitting the feet of the bridge and replacing the nut and the bridge ended up being angled to get the correct intonation, would it make anyone concerned about the quality of the setup? #Is it possible that the grooves in the nut weren't cut properly or that the feet were shaved unevenly? #Would either of those have produced that effect in bridge placement for intonation?

[John Ritchhart]

Maybe the compensated bridge is backwards.

[levin4now]

I will say that I did NOT use the harmonic at the 12th fret, but the fretted note at the 12th fret. I guess I need to check that out. I had never done this before and did it out of memory (and trial and error). I couldn't remember the part about the harmonic.

I'm not worried at all about how it looks, but it just didn't seem to make much sense (physics-wise) that it would be at an angle.

I am at work (sans mando), so I can't check the bridge for reversal, but it seems to me that the groove-size matches the strings so I don't think it is reversed.

Either way, I would like to have it perfect, but for now I'm happy with the significant improvement in sound over what I described in my orig post!

Thanks!

[TommyK]

If intonation is off, the problem is not at the nut but at the bridge. #Intonation is a funciton of scale length (nut to bridge or saddle). #

From Guitar to banjo to mando, all stringed instruments I've seen have the bridge NOT perpendicular to the strings. #This is the nature of stringed instruments. #Probably has to do with the various weights of strings used. #

All fixed bridge guitars have the saddle slot cut closer angled closer to the nut on the high e side vs the low E side. #As with your mando, some guitar saddles are straight, some have a compensated saddle at the high end as a straight saddle is almost, but not perfect. #When I say straight, I mean that if you stand a loose saddle up against a ruler it will be straigt. # The compensated saddles have an addtional cut making the B and e strings a bit longer than a straight saddle would provide. #This is probably due to the fact the the two high strings are plain and not wound. #The mandolin saddle, okay bridge, is compensated as well. #Oh, and by the way, if you flip the mando bridge around, the compensation should be nearly the same. #Try this, Print this post and if the following graphic represents your saddle... Bridge (old habits..) flip the paper over and the low strings are still longer than the ones next to it. #A lefty has to get a custom cut bridge to get the compensation right.

Graphic: ....----....----


I take that back I have seen a guitar with a perpendicular to the strings saddle. #This genius luthier had all the frets and the nut off perpendicular. #A strange looking beast. #At first I thought he did it to impress other luthiers, but now I think it would make fretting barre chords a bit easier. #

If you had a set-up and the intonation was off you got a bad set-up. #Unless, of course, the mando was bumped and saddle moved after leaving the shop. #At the factory, some lutiers will scribe a very light pencil mark where the feet should be. #Light enough so as to not scar the finish, but you have a target for the inevitable event that the bridge gets bump and moved. #

After a set-up or string change, these marks are null and void. #Especially if you change string type and wieght, the bridge will probably have to be moved, a new set of pencil marks and a feet fit.

A careful luthier would have checked intonation in your presence and played a bit, then handed to you to do the same. #This protects him in that you both know that the set-up was proper before it left the store. #If he hasn't, scribe a pencil mark yourself so you know where the feet belong. Again, go lightly, then pack things up and go home.

Problems with nuts manifest themselves as frequent string breakage at the nut, pinging whilst tuning and buzzing of open strings.

A long visit to Fret.com will school any stringed instrumentalist in what he should know about their instrument so as to be a better consumer of set-up and new guitars and mandos.... and yes, banjos.

[AndyG]

You will notice that a classical guitar has a saddle perpendicular to the strings,and not slanted.This is primarily due to nylon strings being near enough all the same guage.
On a steel strung guitar things get more complicated;set ups frequently mean that lower register strings are higher off the fingerboard than treble strings.This leads to a need for compensation for all kinds of complicated reasons.I would imagine the same applies to mandolins,but on a smaller scale(no pun intended!)

[aries753]

I have also had the bridge angled to get proper intonation on the A and E strings. As I am reading this the thought occured to me that after all of my carefull sanding etc to fit the bridge feet to the top it all changes when I skew the bridge. At least on an arched top.