From Banjo Newsletter, 2003
The following question was received from a banjo player in Idaho named Jeff and represents the single most common problem faced by banjo players of all skill levels in keeping their banjo playing in tune. The advice that usually follows this question is often misleading and sometimes just plain wrong. I will attempt to clearly explain the problem and solution.
I just took my banjo apart for the first time to change the head and clean the parts. I followed the advice in a book and the assembly went fairly well. However, now my banjo sounds real strange. It seems the further up the neck I play the notes just don't sound right. I cant understand what happened, the banjo was ok before I took it apart. Did I damage something without knowing it?
Jeff in Idaho
Well Jeff, your problem is likely a simple one. We can for the purpose of this discussion rule out more serious problems that could cause this condition as you mention that it was playing fine before your work. The problem you describe is a classic example of intonation, or more accurately poor intonation. This can be fixed by simply placing the bridge in the correct position. The banjo, more than many instruments can never really be intonated perfectly due to the physics of the five strings and the design of the neck and bridge. Unlike electric guitars which have mechanical adjustment on each string to fine tune the length, the banjo bridge is a solid piece of wood that must be so thin that intonation of each string is impossible. So the best we can do is place is accurately and carefully.
When I set up a banjo, I always use an electric tuner and check the sound of the FRETTED string. Tune the banjo and check the bridge placement by checking the fretted twelfth fret. So many 'experts' recommend using harmonics to check intonation which is as pointless as can be. You fret a banjo to play it and you must check the intonation in the same way it is played or you are wasting your time.
Intonation involves compensating the length of the string from the mathematical perfect length due to the difference in thicknesses of the strings and the distance the string must be stretched to the fingerboard when fretted. For this reason checking bridge position by the harmonics method will always be wrong when compared to the fretted note, and since you fret the banjo to play you should set the instrument up how it will be played. If you only played open strings or played slide style like the dobro the harmonics method is the way to go. This is an important point when discussing string height also. If your banjo is set up with excessively high strings over the fingerboard ( approaching 1/4 inch), it will be impossible to intonate the banjo to play perfectly in both the upper and lower positions. When you play up the neck on a banjo like this the distance the strings must be stretched is so great that it effects the tuning and intonation. You can intonate the bridge position so it plays in the low position but it will be off in the high position. If you adjust the bridge so that it plays in the high position it will be off in the low position.
Assuming your action is about normal (3/16 inch at the last fret) and you have checked the note of the twelfth fret and determined the bridge is in the wrong place, how do you determine the right position? Here again, we will correct a major myth and misinformed piece of advice. How many of you have heard the following, "measure from the nut to the twelfth fret and set the bridge the same distance from the twelfth fret to the bridge"?
Unless you can rewrite every physics book ever written this is impossible. As in checking the harmonics, this doesn't take into consideration string gauges and pressing the string to the fretboard. This is good advice for dobro players. If you fret as we all do, you must compensate by placing the bridge further away from the twelfth fret to adjust the length of the string. So you are asking how much further. Well there is no one answer fits all in this situation. The exact distance of compensation must take into consideration string gauge, string height, and playing style among a few other points. I will give you a tid bit of advice taken from twenty eight years of setting up musical instruments in factories.
Measure from the nut to the center of the twelfth fret. Set your bridge this same exact distance PLUS 2.5 mm (3/32 inch) from the twelfth fret. I have found ninety percent of all banjos and banjo players will be satisfied with this and it checks out on an electric tuner within the range that most people cant hear a problem. If you do hear a slight difference playing the open string and the fretted twelfth, you can experiment with slight adjustments foreword or back. For extremely critical banjo players you can angle the bridge so that the bass foot is slightly further back than the treble, keeping the treble side of the bridge the plus 3/32 distance. But as I have said I have found ninety percent of musicians will be satisfied with the results. This doesn't take into consideration that group of banjo pickers that seem to think every bridge on every banjo is wrong and with nothing but a tin ear to go by move the bridge until it sounds 'right' to them making the banjo unplayable to everybody else.
Well Jeff, I hope you have found some information here to bring your banjo back into good playing condition. Bridge placement and determining the correct position is something every banjo player must understand if you play with others.
Scott Zimmerman - 11-6-03