The bridge needs to be carefully fitted to match the contour of the top plate. The top plates of the two violins probably have some small differences, so it is unlikely that swapped bridges will fit correctly.

Get a competent luthier involved.

You need to decide on the curvature of the bridge that you prefer. Then get a new one made for the new fiddle (it takes some skill to carve a bridge). Do you like a classical curvature or one that's a bit flatter, as I do? My 1st and 4th strings are the same height as classical, but I take off a bit from the middle to lower the curvature.

That bridge curvature is significant. It doesn't take much. The difference of as much as the thickness of a string is significant.  

Oh, you are playing both with the same bow, yes? 

To reinforce what was said previously, take both fiddles to a luthier and have a new bridge made as a duplicate of the bridge you prefer. The second thing to realize, as no two people are exactly alike, neither are two fiddles. Minute differences in the thickness of the neck, the height of the strings, etc. can make a difference in ease of play.

I have one fiddle on which the arc of the neck is actually a little shallower than the other. I believe this is the reason that the bridge is also a little shallower. I recognize that they are different, I love them both, and I play them both regularly.

Every single instrument will have small, individual differences. I recommend that you just appreciate that, and you may even learn to harness the differences for certain tunings, fiddle styles, or specific tunes that use those features best.

Having the bridges fit by the same luthier will increase your chances of getting the same setup. I am considering sending mine off to a luthier in Minnesota. I have one done by a different luthier ... it is well setup, just different. < sigh

The advice to find a luthier and tell him what you want is good. A good luthier should be able to match the playability of both fiddles. I have a 1918-20 Czech Slovakia Fiddle and a 2010 Chinese Ma Zhibin Fiddle. They sound different but he set them up so they play the same. Very easy to switch back and forth, which I do all the time.

It shouldn't be a problem to get the bridges very close. Notice I said very close. Keep in mind the curvature of the finger board may effect the curvature and the outcome. Violin Beautiful knows these things,

Thanks everyone. Good stuff.

I enjoy the fact that my three fiddles are all set up slightly differently, and that they are all of slightly different weights. I have individual shoulder rests for each, as well...though I do wish that the pad of one of the shoulder rests had slightly more grip on my shoulder (I've tried to rough the shoulder pad up a bit but it hasn't really worked). I'm the same way with my various steel string acoustic guitars. In addition to the differences in tone I like the variety of touch and feel each offers. It inspires me.

"About the same" may not be close enough in this case - people can feel quite small differences in playability.
However, you can make some simple measurements for comparison if you want to take the time, with only a 6" rule (reading in mm), a straightedge, and maybe a set of feeler gauges.
First, measure the distance between the bottom of the string and the fingerboard, at the end of the fingerboard. Only a half a mm can make a difference here.
Then you can measure the string height at the bridge. If you also measure at the center of the bridge and both edges, you can draw the curves of the two bridges, and even make paper or cardboard templates for comparison. As others have said, the curve of the bridge should roughly match the curve of the fingerboard, so there are limitations in what you can do.
People don't always appreciate how much the string height at the nut affects the feel of an instrument, since this is where your fingers are actually placed. Since there are no frets involved, this can be very low on a violin, and can be measured with feeler gauges for comparison.
With a straightedge you can compare the relief ("scoop") of the fingerboard, and its position between the two instruments. You can also look for any other low spots or bumps that can affect playability.
So with simple tools, you can make some comparisons between your two violins, although I think some instruments just feel more "playable" than others, even though they may measure very close to the same.
Or you can just take both instruments to your luthier and ask if they can make #2 feel as close as possible to #1 and see what they can do.

THink about this - if you get the classical bridge curvature on both, you'll be able to have any violin luthier make a new bridge (when your current ones go bye bye) and it will feel the same. If you have custom bridge curvature, well the next luthier may not be able to make it exactly the same. Flatter bridges do make string changes slightly easier, for them's lazy fiddlers. I like working for my string sonority. And I ain't doublestopping by accident. To each, his own.

One thing that's very easy to do without taking measurements is take something like a round #2 pencil, which should be about 7 mm in diameter, and lay it flat against the fingerboard between the strings. Even without making any marks, you should be able to see how high the strings are on the bridge above the pencil tip.

I have a 7 mm round (Spider Man) pencil that I keep for such purposes.

I'm comfortable re-cutting bridges. I strongly prefer to have a luthier fit a bridge, but if the bridge action isn't what I want I'll change it, especially on lesser instruments. I'm not going to give my process as I don't want to imply that you should do this yourself. But the 7 mm diameter Spider Man pencil is an important part of it!

I have a fiddle that I had set up years ago with a classical action. I completely forgot until I compared the string height with the pencil tip.

quote:

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Originally posted by RinconMtnErnie

One thing that's very easy to do without taking measurements is take something like a round #2 pencil, which should be about 7 mm in diameter, and lay it flat against the fingerboard between the strings. Even without making any marks, you should be able to see how high the strings are on the bridge above the pencil tip.

I have a 7 mm round (Spider Man) pencil that I keep for such purposes.

I'm comfortable re-cutting bridges. I strongly prefer to have a luthier fit a bridge, but if the bridge action isn't what I want I'll change it, especially on lesser instruments. I'm not going to give my process as I don't want to imply that you should do this yourself. But the 7 mm diameter Spider Man pencil is an important part of it!

I have a fiddle that I had set up years ago with a classical action. I completely forgot until I compared the string height with the pencil tip.

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Hi Ernie, don't worry, my fiddles are certainly in the "lesser" category!  Messin' around with instruments is very much a big part of why I like to play instruments in the first place.   Oh, the things I did to my first fiddle before I knew that only a qualified luthier should do those things! 

quote:

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Originally posted by wrench13

THink about this - if you get the classical bridge curvature on both, you'll be able to have any violin luthier make a new bridge (when your current ones go bye bye) and it will feel the same. If you have custom bridge curvature, well the next luthier may not be able to make it exactly the same. Flatter bridges do make string changes slightly easier, for them's lazy fiddlers. I like working for my string sonority. And I ain't doublestopping by accident. To each, his own.

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I think that that the fiddle I prefer is neither classical or fiddle curvature.  I think it's a little bit of both. Something like Carl mentioned above. 

There are a lot of details that go into a setup. The bridge is just one part of it, and even that has its own set of details. When you play the violin you’re experiencing a system that works in concert to get good playability and sound.

There is a curvature template for violin bridges that is widely used by almost all good shops. You can find this in Strobel’s book or in the Weisshaar book or in Morel’s templates. It isn’t simply a section of a circle, but is refined to allow the greatest playability among all four strings. The fingerboard, when set up properly, will have a certain profile longitudinally and latitudinally. If the curvature of the board is correct (don’t even get me started on how often this ISN’T done properly!) the bridge template will give the best curve that works with it. If something is off, it either needs to be corrected or you have to begin making sacrifices to get a more workable setup.

Other things like nut height, afterlength, neck shape and thickness, neck length, stop length, vibrating string length, projection, neck heel shape, scroll chin shape, and even the edges of the fingerboard all have an impact. The soundpost and bridge have the most obvious impact on sound, but everything matters.

I was just about to mention how curvature of the fingerboard and bridge are part of the same equation, but Rich beat me to it.

Here's how I learned this: my current luthier/wizard offhandedly recognized the mismatch of a bridge and fingerboard on a fiddle I took in to have a seam reglued. He offered to fix that (more money, of course) and the fiddle never played better. Turned out the various guys who cut my bridges essentially only fitted the feet and cut a standard looking bridge. True confession: one of those fiddles had a bridge profile cut by a younger me.  Later, Randy said and showed to me that two of my fiddles had just plain bad fingerboards (as Rich mentions, poorly shaped) and one was worn some and needed to be planed. 

I had all of my fiddles re-setup after that and, to slightly varying degrees, they now all play easy and smooth like butter.