Evaluating archtops - bridge question
 

I am in the market for an archtop and spent some time today playing 6 different Eastmans. I learned a lot. I was very impressed with all of them across a wide price range. I also learned I shouldn't get a 17-inch one. Just too wide for me. Sounded great though.

Here is the question. All of the instruments seemed to be set up nicely. One or two of them had none or almost no remaining "travel" on the adjustment posts on the floating bridge. Most of them had, I would guess, about 1/4 inch or a little more adjustment left on the posts. None of them had the bridge really high.

How much of a concern should this be? Am I correct that if there is no adjustment room at this point, then the bridge itself will have to be thinned down the road if the adjustment is needed later? Or, should it not be of great concern if the instrument is currently set up fine?

Thanks.

Travel in which direction?

The adjustment was pretty much all the way down -- the bridge was as low as it could go using the screw adjustment posts.

When I look at an acoustic archtop made in the traditional pattern with a floating bridge, I look for the string height above the top (total bridge height, in other words) to be between 1" and maybe 1.2". That suggests to me that the neck set and angle is correct for traditional built instrument. If I see much less than that, then I look to see if the string break angle is less than ideal (for me, ideal is 14 degrees). If the bridge height is low and the break angle also low, then in my view the instrument is wrong and won't perform to optimum, since the top needs a certain amount of preload.

If the string break angle seems good and the string height is in the ballpark, then I look at the bridge. Keeping in mind that making a new bridge piece is pretty simple and non-invasive, I look at the current action at the 12th fret. If it's in the ballpark of 1/16" for the high E and 3/32" for the low E, I look at the adjustment range. I would want to see at least 1/8" of down adjustment to accommodate changes in humidity, settling of the neck joint and body, etc, and 1/4" is just fine. Small changes in action will require twice the adjustment at the bridge, as is well known, some future adjustment to neck relief might ask for a tweak to the bridge height, time will inevitably lower the bridge height as the guitar settles, so you want some adjustment.

More than you probably wanted, but asking about the bridge is the starting point only... :)

I look for about 1/4" of travel in either direction, without the bridge being too high/low - IME all the rest of the geometry Brian describes tends to fall within spec...

If you needed to lower the saddle, you could remove material from the part of the saddle the contacts the thumb wheels. If there is not sufficient gap between the bridge and the saddle, you could also remove material from the under side of the saddle.

My Eastman AR503CE was setup similarly - not much of a gap between the bridge and the saddle. In my case though, I actually raised the saddle slightly so it hasn't been an issue for me. Was not concerned that the bridge could not be lowered much more than say 1/8" because I figured I could always sand down the saddle if necessary.

Thanks for replies. Very helpful.

Crossing my fingers that I am not misunderstood.

When shopping for a vintage archtop guitar, when the saddle is cranked down "too low" for good playing action on a bridge base of standard thickness it is indication of a neck reset. If the bridge base is sufficiently "thick", you may thin it down to postpone getting the neck reset. But a good healthy neck angle is essential to getting a good tone. A Gibson archtop has a 4 degree neck angle, if I am not wrong.

When a saddle is cranked up "too high" for good playing action, this is an indication of a sinking arch. Another tell is to look at the f--holes to see if the inner edge is not on a plane with the outer edge.

A "healthy" bridge usually measures about 1" from the highest point of the saddle to the arch of the top, give or take a little.

On new Eastmen, if some are cranked down too low, see if you could lie them down side by side and check the neck angles. Check the bridge bases to see if some are way thinner than others. They should all look and measure the same give or take a few hundreds of an inch. If there is only one, it is difficult to eyeball the neck angle.

When a base is thin from the factory, a lot more bridge post is going to be exposed. This makes it look "high" or "low"as the case may be.

On those you see with little or no travel, how thick is the bridge base? If it looks unhealthily thin, you got to inspect the neck angle next. Of course, the guitar could have an unnaturally high arch but that is unusual and it would be rather obvious. A healthy bridge base is about 3/8" thick at its thickest section. A wooden saddle is about 3/8". That leaves about 1/4" post showing.

A luthier can shed more light on this. I stand to be corrected.

PS An acoustic archtop guitar requires higher playing action to sound its best. Electric players may require very low action outside of the adjustment range of a standard bridge. This could result in the saddle "bottoming out" for preferred playing action. Nothing wrong with neck angle in that case.