A Scientific Method for Determining the Correct Head Tension For Your Banjo
Banjo Setup File #2
The first critical adjustment in banjo setup is the head tension. No matter what kind of banjo you have, this is the one place where you can make the most difference in the sound of your instrument with the least amount of monetary investment.
In the old days, banjo players generally believed that the tighter you could get the head of the banjo, the better it would sound. This was actually fairly true in the old days of goat- or calf-skin heads. However, with modern materials, such as mylar, etc. it is quite possible to overtighten the head of your banjo. In fact, mylar, the material that serves as the base of most modern plastic heads, has 1/3 the tensile strength of steel. More than one modern instrument has suffered structural damage from overtightening the head. The next time you go to a bluegrass festival, take a look at how many banjos have resonator flanges that have been bent out of shape by excessive head tension. The older skin heads had a safety feature built into them. If you overtightened them, they would stretch or even break. Mylar doesn't do that. It stretches to a certain point, then either pulls off the rim (or flesh hoop), or it destroys the banjo. I might add that skin heads were capable of bending a resonator flange. At a recent IBMA, I saw a flathead PB-4 that had a flange that had been severely distorted. It had a skin head on it. This head was quite thick.
Many people have different theories as to the correct tension of the head of a banjo. Mine was developed by experimentation.
In 1971, John Ike Walton, drummer and banjo player for the 13th Floor Elevators, stayed with me for a couple of months. He had a Fender Artist's Model banjo, which was very similar in construction to a Gibson Mastertone. As we discussed the setup of the instruments, John started thinking out loud. "You know, it is possible to tighten a drum head so much that it chokes off the sound. Well, a banjo is just a drum that is being used as a sounding board for your strings. Every drum has a certain tension where it sounds better. I'll bet that's true for a banjo, too."
What We Did
This sounded logical to me. So we took the strings off his banjo, and proceeded to adjust the head tension the same way he adjusted the tension on his drums. We drew a line on the head about 3/4" inside the edge of the tension hoop, and we tapped the head directly in front of each bracket, right on the line, with a makeshift drum stick. As we tapped, we would adjust the bracket, until we found that one frequency where the head seemed to come alive. The sound would become markedly louder when we reached the correct tension -- sort of like this -- bonk, bonk, bonk, bonk, BONK. We started with the pair of brackets at the base of the neck, that is, the pair on either side of the base of the neck. Then we adjusted the pair at the tailpiece. Next, the pairs 90 degrees away from the first pairs--working the compass points, so to speak. If you think of the neck as "North" and the tailpiece as "South," then the sequence of tightening was North, South, East, West, Northeast, Southwest, Northwest, Southeast. Then we adjusted the remaining single brackets between these bracket pairs in a similar fashion.
To give a numerical sequence to this, imagine that you are looking at the banjo rim from the front. The bracket to the immediate right of the base of the neck will be #1. The one to the left of the base of the neck will be #24. Tighten them in the following order:
You may need to repeat this procedure a couple of times until the tension stabilizes. Usually when you are loosening the head only one repitition is necessary. Now, back to the story.
We did this until each bracket was at the right tension. Amazingly, we had loosened the head slightly, yet it felt even firmer than before--possibly because the tension was so even. When we restrung the banjo, it sounded wonderful--even better than my Mastertone, which before had been the better of the two instruments.
Naturally, we did the same thing to my instrument, and it sounded even better than before. I have done this to many other banjos since then, and I have found that each individual banjo has its own specific resonant frequency. This stands to reason, because of slight differences in the mass of the tone rings, the body woods, the thickness of the head, etc. Some technicians believe that an arch top banjo should be tuned to a B, a flat head to an A, etc. Again, I have found that each banjo is slightly different. Try my system on your banjo and see the difference it makes!
When you try this, remember to tap gently, but firmly. If you have an actual drumstick, let the weight of the drumstick do the work. Don't POUND on the head, but just tap it. A piece of a dowel with a rounded tip will also work well. Also remember to tap directly in front of the bracket you are adjusting.
When you are finding the correct tension for your banjo head. It is very important that you begin with a tension hoop (stretcher band) that is totally flat. Otherwise, it will be difficult, if not impossible to apply totally even tension to the head.
If you decide to straighten out your tension hoop before adjusting the head, the process is simple. Place the tension hoop on a flat surface--lower edge downwards. When you find a bend in the hoop, gently bend it in the opposite direction until you have straightened the hoop out. Then install the head and tension it properly. This idea was submitted via e-mail by Brent Carlson.
If you don't want to go through this process before you replace the head of your banjo, but you do want to try the head tuning technique, you will find that you will noticeably improve the sound by following the tensioning instructions, even if your tension hoop is slightly bent.
One other thing -- always check to make sure your head hasn't pulled loose from the flesh hoop before you try to adjust the tension. This may sound like a "no-brainer," but it really isn't. You don't need to take the head off the banjo to do this. Just push down firmly at several places around the circumferece of the head. If it gives, you probably have a damaged head.
One very important note
Tuning the head to the resonant frequency of the banjo is just a start. You may find that the banjo has more emphasis on the notes up the neck than on the ones in the bass. A lower head tension generally causes the bass to be more emphasized. A tighter head produces better treble. Let me clarify this -- I don't mean that you will get cannon-like bass out of a banjo, simply by loosening the head tension. Nor will you have a screaming treble if you adust the head until it is about to break. I am speaking of minor tension adjustments. A sloppy head is not the answer for a good sounding banjo. Neither is one that is as hard as concrete. There is a point (or points) somewhere in between that will give you the sound that you like best.
There is also a remote chance that when you find the "hot" frequency for your banjo, that is, the proper tension for the maximum volume, that you will run into a situation in which the banjo has one or two notes that are overpowering. This is a rare occurrence, but it can happen. Check the note that the head is tuned to. If it is tuned to a G a B or a D, you will have a situtation that produces a type of "wolf" note. These are notes that vibrate uncontrollably. The problem here is that you have the head tuned to the same pitch as one of the open strings. This is not a good situation. Every time you play that note, it will roar!
For example, if your head is tuned to a G, every time you play an open third string or an open 5th string in G tuning, you will have a note that is overbearing. Here's the solution.
Determine whether the banjo needs more bass or more treble. If it needs more bass, loosen the head very slightly -- so that it is tuned somewhere between an F# and a G. If you tune it directly to F#, you will get a wolf note when you play a D& chord. If the banjo needs more treble, tighten the head very slightly, so it is between a G and an Ab. If you tune your head to an A, you may have a wolf note every time you play a D7 chord or an A chord.
Drum Torque Wrenches Now Available Via Internet!
One device that has helped me greatly in adjusting head tension accurately is the Neary Drum Torque. This is a special torque wrench developed in Canada for equalizing the tension on drum heads. Once I find the correct tension for a particular instrument, I make a note of it and I use the Drum Torque to set the tension in the future.
Important!!!!! Determine the correct tension by tapping the head before you try using the Drum Torque. Each banjo differs slightly from the others. Also, each of these inexpensive torque wrenches is an individual. It is not possible, as far as I know, to recalibrate them.
This is now available from Janet Davis Music. and from Hatfield Music. Check with the respective music dealers for pricing. Hatfield Music also has a banjo setup kit available, which contains various pliers, cutters, screwdrivers, etc.
I have modified mine slightly. The Drum Torque comes with a special fitting that will straddle a banjo wrench while it is on the bracket nut. I found it very convenient to permanently attach the bracket wrench to the "straddle" fitting with ribbon epoxy (available in auto repair shops, hardware stores, etc.) If you wish to do this, order an extra bracket wrench. You will be glad you did!
Conversion Table for Torque Wrenches
contributed by Ronald R. Hewitt Cohen
This chart will enable you to use any torque wrench within these ranges on your banjo. Torque wrenches that measure in foot pounds will be difficult or impossible to use because they fall out of the range of normal banjo head tensions. Thanks, Ron, for permission to use your chart.
Replacing the Head
First, make sure the tension hoop is flat and straight.
Examine the inner edge of the bottom of the hoop. If it has any sharp areas or burrs on it, remove them with a file, a rasp or some emery cloth. Burrs and/or sharp spots can cut into the head. Modern tension hoops have a chamfer on the inside of the bottom. It's a good idea to put one of these on your hoop if your banjo is not an antique and you are not planning to use a skin head.
Make sure it goes on evenly and seats properly. Installing the hooks in the order I have given for tightening them virtually ensures that the head will be seated properly. Get those first four pairs in place and make sure they are even before you try to start making adjustments. Do not try to reseat the head by simply tightening down more on one side and loosening the other side. You are almost certain to damage the head if you do that.
Once you have installed the new head, tighten it evenly and let it sit for a few hours, even overnight, if necessary. Then come back and tune it properly. If you install it a little tighter than you would normally install your head, it will settle in a bit more quickly and will not require as much time to adjust.
If you have an archtop or raised head banjo, you will need a medium crown head or a low crown head. If you have a flathead banjo, you will need a high crown head or a medium crown head. The height of the crown determines where the top of the tension hoop sits, which, in turn, determines how the tailpiece sits. Using a high crown head on an archtop banjo may cause the tension hoop to be so low that the tailpiece rests directly on the head. This can cause undue stress on the tailpiece in some cases, and can also cause the tailpiece to dig into the head. I have seen more than one banjo head destroyed by a tailpiece that cut or broke through it.
"Windows" of Tension
In discussing setup with Kyle Smith, well-known banjo setup man, I have often heard him refer to the different "windows" of tension for the proper setup of a banjo. He has a special, proprietary process that he uses to determine the proper head tension for a banjo. He quite often will find three different tensions that produce similar results. These will be three different points at which the banjo assembly comes to life. I have noticed this, myself. The ranges on these will somewhere between 6 and 17 kg-cm. I won't go into the physics of this. I have noticed that certain people in one part of the country will swear by 6 kg-cm. Others like 11 kg.-cm. Still others prefer 17. The whole point of my mentioning this is that with banjos that sound good in any of these particular ranges, they are neither muddy nor strident, and they have good note separation. One of the banjos I took to IBMA 2003 was adjusted to 11 kg.-cm. A similar instrument at 17 kg.- cm. had a remarkably similar sound. Which one is correct? Both of them! This brings up something that is quite important:
There is no "magic number" that works on ALL banjos!
When you are adjusting your head tension, tap-tune it as I have described. Find the point where it sounds the best to you. Then measure that and keep a record of it. But don't just go cranking away at it with your torque wrench. That is a sure road to failure!!!!
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