Setup Series - Step 3: Bridge set-up

Once the banjo head, truss rod and coordinator rods are adjusted we'll move on to the bridge. The bridge adjustment, wood used, and shape of bridge greatly affect the tone, but also its final height will determine the string action.

There many theories on bridges. This explanation is based on my hearing evaluation and experience on setting up thousands of banjos.

Banjo bridge styles, construction designs, and shapes are endless.  Since a bridge is easily replaceable, it's probably the most common part replaced by a player to experiment with desired tone. 

Grover Minstrel bridges, introduced in the 1930's, have become the standard for shape and design.  This bridge is 3 footed, close grain maple and has an ebony cap. Ebony is a very hard wood, is commonly used as a cap, as it prevents the string from deepening the slot and has good sound properties. Bridge makers have explored many variations by experimenting with different woods and a variety of shapes. There are two foot, three foot, compensated for improved intonation, graphite bridges, tipless bridges and many more variations.
 
The bridge is the first link in transferring the string energy to the head; so size, height/width and mass really matter. Generally, the lighter the bridge, the louder and more bright the tone, but if too thin or too light, the string tension will easily warp the bridge, as the feet are anchored on the head which naturally curves down from the string tension. 

5/8" height is most common, a standard probably because it allows the best technique position for the right hand as the 4th and 5th finger anchor the hand. 11/16" and other taller heights are also used.  Bela Fleck uses an 15/16" bridge.  He reasons a higher bridge increases the break angle at the bridge and provides a better tone. Bela is very particular about bridge choice, height and wood type.  Bob Carlin will choose a bridge (he likes tight grain aged maple with ebony cap) and then adjust the head so it sounds best with that particular bridge. Both methods make sense, and the player may try a little of both.  Grover also makes a 1/2" height, really too low to the head for optimum  tone (decrease break angle) and right hand technique. It is most often used as an easy solution to lower the string action. If you are using a 1/2" bridge, readjusting your neck angle and increasing bridge height will definitely improve your tone.
 
Compensated bridges are generally heavier and not the best for tone. The Moon bridge is fairly light and curved, so its tone is superior to a Grover. Our solution, and other makers. is to use a straight bridge with a small routed cutout on the third string. This lengthens the third string scale. The third string, because it is the thickest plain string, is always troublesome for intonation.
 
Most often the bridge is made of close grained maple and then an ebony cap. Makers have experimented with every type of hard wood and they all are noticeable difference in tone. For sure, aged maple, 30 years and older, sounds best to most. The best bridges we ever made came from a old basketball floor, built in the 20's. Besides the age, after thousands of basketball games, it was well compressed!

String space notch standard is the Grover spacing, but custom spaces may be needed for a non standard width neck so the strings are the correct distance from edge of fingerboard. Since bluegrass banjos have a typical neck width, the Grover spacing is common. In recent years Crowe space notches have gained popularity. Slightly wider than standard, many players claim more comfortable right hand picking. Try both for your favorite. Old time necks are made often with wider fingerboards but most still use standard string spacing.

Installation and Adjustment

Bridges are changed because:

1. You want to experiment with different bridges for fine tuning your desired tone.
2. The top edge of the bridge will sag in the middle. Its unavoidable, and once curved the strings would not be level. The only bridge I have seen that will not curve is a graphite bridge.
3. You want to fine tune the string action and use a different height. 

First, make sure you have installed a new set of your favorite string gauge. To properly place bridge for correct intonation, measure the distance from middle of twelve fret to the nut (the point where the string exits the nut). A yardstick works perfectly and you can pencil mark the location on the stick. Then place the ruler tip edge on the middle of the twelve fret (highest point on fret crown) and locate the front edge of bridge that distance. Now use a digital tuner to precisely locate. Tune at correct pitch. Now gently fret the 12th fret and check with tuner. If this note is sharp move the bridge towards the tailpiece. Flat move towards neck. Retune and recheck. Then repeat on the 4th string. It's normal to have some slant. Using a sharp pencil, you can mark on the head it's location. 

Sanding the feet thinner will improve tone ...although too thin you will lose support. This is also a way to lower action. To sand feet thinner, we use  120 sandpaper glued to a piece of glass, then 220, and finish with 440. The trick is to sand feet level so the bridge is perfectly straight when installed...

Bridge Hints! 
 

1. A very common problem is a plucked fretted note sounds dull or "fuzzy" on every on every fret on the same string. If changing the string does not solve the problem, simply re-cut the notch (with correct nut file) and make angle of cut = to the angle of the string going from bridge to tailpiece. So instead of the notch angle being parallel to the head, its parallel to the string angle behind the bridge (If only the open string is dull or fuzzy, the nut slot needs a similar adjustment, not the bridge slot).
2. The strings should be exactly level with each other so check with a straight edge tool. After filing notches so strings are level, sand the top edge of the bridge level with top of strings. On wound strings the notch depth is 1/2 the thickness of the string, so the top 1/2 of string is above the plane of the bridge.
3. If you do sand the feet thinner, to optimize vibration transfer, you can make a slight truss rod or coordinator rod adjustment to raise action if needed.  
4. I check different bridges often for tone quality. In my experience, its a challenge to accurately remember a previous tone to make the best choice in comparing different bridges. Also, when you test, you must also play from the lowest to highest note. So my method, unavailable to most, is to have two of the exact same banjos, equally set up.. . with two different bridges. A helper sits in front of me holding one banjo, and the moment I finish playing licks on one bridge, I quickly change banjos and replay the same licks. I do this at least a dozen times before I make my final judgement. Mr. Fleck, who IMHO has the best set of "banjo ears" on the planet, uses the following method to confirm. He makes recordings of each bridge and then compares. That's probably the best confirmation technique.

Next well talk about the nut.. Comments are always welcome!!! 

Wayne A. Rogers
President and Founder
3656 Hopkins Ave.
Titusville, Fl 32780
www.goldtone.com

Setup Series - Step 2: Fret Levelness and Truss Rod Adjustment

Setup Series - Step 1: Adjusting the Head