Finding the right head tension for a 12" banjo

This week I thought I'd discuss what I consider to be the most important piece of banjo setup: proper head tension. There are a lot of people out there who have likely never adjusted their banjo's head tension but I take the opposite approach: I typically check my head tension every couple of weeks (yes, synthetic heads do fluctuate on occasion) and consider head tension maintenance to be a non-optional piece of overall banjo maintenance. Later in this post, I'll post sound files of the Buckeye at different head tensions to demonstrate how important it is for proper sound, but first lets discuss the basics:

How do you check and adjust head tension?

One oft-quoted approach to checking head tension is as follows: "if the banjo sounds good, the head tension is correct." Obviously this is true; however this approach is not all that useful for diagnostic purposes: For instance, what if the banjo doesn't sound good on day? Is the head tension the issue or is there another reason? If the head tension is the issue, does the head need to be tightened or loosened? I prefer to use a more-objective method of measuring head tension when the banjo does sound good, then I know if/how the head tension should be adjusted when the banjo doesn't sound good. Some commonly used objective methods to measure head tension are as follows:

1) Tap tuning the head - Basically you mute the strings, tap the head, and listen for a note. I'll admit that I'm terrible at hearing the note here - I can usually convince myself that the head is ringing at several different notes. I read a recent post on banjo hangout where someone was claiming that the note we're looking for is actually a low frequency note that is outside the hearing range of many people (caveat, I have done absolutely no research into the truthfulness of this claim). I can tell you that this particular approach doesn't work well for me - however I will revisit tap tuning (with some audio!) later in this post. If you can hear the note, most people say a banjo head should be tuned to G# using the "tap tuning" approach. 

2) The ruler/straightedge method - This method measures bridge displacement as a proxy for banjo head tension. The logic of this approach is as follows: the pressure of the strings will push the bridge downward into the banjo head; this displacement will be greater on a looser head than it is on a tighter head; there is a "goldilocks level" of bridge displacement indicative of the head tension at which the banjo sounds best. There are details of this method on banjo hangout, but the procedure is basically as follows: get a straightedge (I think they specify a 10" straightedge) and lay it across the head next to one foot of the bridge. Most people recommend that you should be able to slide a quarter under the straightedge next to the bridge. This seems to be the recommendation for an 11" banjo and I have no idea what the "ideal tension" for a 12" banjo would be using this method (less then a quarter? more?). Also, its a little problematic to me that string tension and tailpiece tension could affect bridge displacement as well; still this is a very quick and easy measurement and maybe I'll look into something similar in the future.

3) The torque wrench method - This method measures the tension on each hook as a gauge for head tension using a tool called a torque wrench. The logic here is that tighter hooks mean a tighter head and looser hooks mean a looser head. This may be true on average but it doesn't allow for friction differences between hooks (maybe one nut just fits a little better than another?). Also, it seems like the ideal amount of tension you're going for should depend on how many hooks you have so I'm not sure what to do with recommended values for the torque wrench method on my 26-hook buckeye.

4) The Drum Dial - This is my preferred method for checking head tension. The drum dial is a piece of equipment that, as the name suggests, is commonly used by drummers; since a banjo is basically a drum with a neck on it, the drum dial works great for our purposes as well. If you lift up the drum dial you can see that there is a little piece of metal sticking out the bottom; this piece of metal is connected to a spring and if you push it in with your finger the number on the dial changes. Basically, the drum dial measures resistance against this little piece of metal sticking out the bottom. If you put the drum dial on a banjo (or drum) head, it will display a number greater than 0 which is positively correlated with head tension (the higher the number, the more tension in the head). To me this is advantageous because you're directly measuring head tension rather than a proxy for head tension. Most discussions recommend drum dial tensions between 90 and 92.

More on the drum dial:

(Note that there are plenty of videos about using the drum dial as well, many of which are likely more informative...but here I go).

To use the drum dial, first it must be "zeroed" by placing it on a hard surface and making sure it measures zero (really, this is a measuring of "100" - the dial goes all the way around the circle to get back to zero). When I say a hard surface, I mean a really hard surface: metal is best though I have hard tile coasters I normally use. My coffee table is a little too soft (it will measure more than zero even when the dial says zero sitting on my coaster); my coffee table is not the highest quality wood however : ). If the hard surface doesn't measure zero, turn the dial on the front of the drum dial until it does (you're basically adjusting the whole scale of the drum dial to set the new 0/100 value is by doing this).

Next you're ready to place the drum dial on your banjo head (about 1" from the edge - there is a gauge that comes with the Drum dial for this) and see what it says; this process should be done with the strings on the banjo. My drum dial is a bit old and often has to be wiggled a little bit to settle on the correct number. Measure the tension at 6 to 8 points around the head; hooks can be tightened or loosened to achieve the correct tension in a given region - ideally head tension will be even everywhere you measure. A quick tip for overall hook tightening (e.g. changing head tension from 89 to 90): some people will say that hooks should be adjusted in a star pattern or something similar - The buckeye has 26 hooks and I'd likely screw that up...I simply go hook by hook in order to adjust tension, usually not turning each hook more than 1/4 turn, and I've talked to several builders who use the same approach.

But what drum dial reading is best for a 12" banjo? As mentioned above, most people on Banjo Hangout say the best sound is somewhere between 90 and 92 (as an aside, they say this correlates to a  head tuned to G#); however most of these people are playing 11" resonator banjos. I had a 11" white lady banjo that sounded phenomenal at 89 but really "choked up" and lost bass notes at values of 90 or more.

Would we expect a 12" pot to need a looser or tighter head than an 11" pot? It seems like a banjo head should work like a banjo string: just as a thicker string needs more tension to make the same note as a thinner string, a bigger banjo head should actually require more tension to make the same "resonance frequency" as a smaller head. However, that approach assumes that a 12" pot should have the same resonance frequency as an 11" inch pot - perhaps the larger chamber of a 12" pot really "opens up" at a lower resonance frequency? I bought a 12" banjo for increased bass response over an 11" banjo; perhaps I should adjust the head tension towards more bass than I would want for an 11"?

So many questions.....the only way to answer them is to go into the lab! 

Testing different head tensions on the Buckeye

To figure out the "perfect" head tension for my 12" banjo (post about my Buckeye available by clicking here), I cranked the head to even tensions of 84, 86, 88, 90, and 92 as measured by my drum dial (once again, with the strings on). This is a pretty wide range of tensions so I'm pretty sure the right answer is in that range somewhere : ) I tuned the banjo to double D (aDADE), mostly because this is the tuning that I spend most of my time in, and played through both a 2 octave D major scale and an "AB" version of "Spotted Pony" at each tension. Also, I am a big proponent of head stuffing to kill overtones (yes, this is blasphemy to some!) so all of the audio files below are played with a small folded over rag stuffed between the dowel stick and head at the top of the pot (where the neck meets the pot). Finally, the banjo has a no knot tailpiece and renaissance head (just FYI).

How do I know which tension is right? What I'm looking for is a good balance of "booming bass" and "cut" (mid-range tones that would allow the banjo to be heard in a group). I used a cluck-heavy version of spotted pony because I also wanted to see how head tension affects cluck. On to the results!

Head tension 1 - Drum Dial reading of 84

2 octave D major scale (left) and "Spotted Pony" (right) played on the Buckeye
​with a head tension of 84 as measured by the Drum Dial

Comments: The open 4th string sounded crazy boomy at this head tension, which I loved...but it was really hard to bring out the cluck and the high notes sounded "warbly" rather than clear. Definitely sure this is too low of a tension value...

Head tension 2 - Drum Dial reading of 86:

2 octave D major scale (left) and "Spotted Pony" (right) played on the Buckeye
​with a head tension of 86 as measured by the Drum Dial

Comments: This was a big improvement over the last tension (especially in terms of the "warbly" high notes) but it still sounds like a banjo that could use head tightening, mostly due to lack of "cut." Still like the low end though : )

Head tension 3 - Drum Dial reading of 88:

2 octave D major scale (left) and "Spotted Pony" (right) played on the Buckeye
​with a head tension of 88 as measured by the Drum Dial

Comments: I feel like I'm getting close to ideal here! Still some bass afoot, but the "cutting mids" are coming in and its getting easier to put the "cluck" into spotted pony.

Head tension 4 - Drum Dial reading of 90:​

2 octave D major scale (left) and "Spotted Pony" (right) played on the Buckeye
​with a head tension of 90 as measured by the Drum Dial

Comments: This sounds pretty good, but in my opinion the high notes are a little out of control...also the cluck is a little obnoxious (definitely much louder than the other notes). I may have overshot at this point.

​Head tension 5 - Drum Dial reading of 92:

2 octave D major scale (left) and "Spotted Pony" (right) played on the Buckeye
​with a head tension of 92 as measured by the Drum Dial

Comments: Yeah this sounds terrible - super nasal and the notes are "choked" (i.e., the notes have a severe loss of sustain). I thought it was worth testing this tension because my 11" banjo sounded so good at 89 and I felt that this was a necessary data point for testing the aforementioned "maybe bigger pots need higher tension" hypothesis. I'll admit I was a little terrified to tune the banjo head up to 92 but actually it was no big deal (as in, the head didn't actually bust or seem like it was close to doing so). However, I'm pretty sure I'm going the wrong direction by tightening this much and don't need to test any higher values : )

A Quick Return to "Tap Tuning"

​While I had the banjo head dialed in to these different tensions, I thought I'd go ahead and tap the head at each one to see what this sounded like - perhaps I could even improve my tap tuning skills. I tapped the head with my fingernail halfway between the bridge and the edge while I muted the strings. The banjo was "unstuffed" (rag removed from beneath the head) for the tap tuning trials. I combined all of this into one audio file below. I can definitely hear that the "note" (or collection of notes) gets higher each time, but I'm still not confident enough to figure out which note each one is supposed to be : )

Head taps at a variety of head tensions as read by the drum dial. 8 taps each (in 2 groups of 4) at increasing head tensions: starting at a drum dial reading of 84, then 86, 88, 90, and ending on 92.

​Conclusions:

The best head tension for my banjo seems to be somewhere in the 88-90 range; obviously this may differ banjo to banjo but its interesting that the "ideal" value for my 12" banjo is roughly similar to what worked for my 11" banjo. I may try 89 for a while - its kind of hard to know which tension provides enough cut until you find yourself in a jam so I'll have to report back later on how the Buckeye handles in a group at 89. I wasn't sure how well the recordings would capture all of this  and perhaps they dot measure up with my comments I've written on each tension to your ears. However, I think that the Yeti mic did a pretty good job overall (especially compare the 84 recordings with the 92 recordings with some decent headphones - pretty stark differences!)

One final caveat: I used the same bridge (21/32" buckeye bridge) for this whole process. As the head tightened, the bridge raised and so did the action. Therefore, there was a higher string angle at higher tensions, which gives higher downward pressure on the bridge. Typically, increasing downward pressure on the bridge increases the mids and decreases the lows....essentially the fact that the string angle increased as head tension increased likely exacerbated the effects of head tension in the recordings. In an ideal world I would have changed bridges to incrementally lower height (but somehow same weight?) bridges with each change in head tension - however, I'll likely use this bridge on the banjo at 89 so perhaps this was the perfect test for my purposes : )

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Before I go, a quick rundown on the first gig of "Rock Andy," my new old time duo with a local fiddler (we will likely do some trio gigs with an added cellist in the future as well!): we played at a local food co-op yesterday and just killed it as background music : ) I think we're my favorite band now (I may have to get a "Rock Andy" T shirt) - unfortunately I didn't record anything to post here...I'll have to be a little more diligent with that in the future. Stay tuned!