Photo 1 — More basic than Leo’s Esquire, our author presents his test rig for measuring string tension at varying headstock lengths.
Who doesn’t like myth-busting? The act of disproving something that is generally considered true is just the kind of smack-down justice that people find both entertaining and eye-opening. I’ve had a lot of my beliefs shot down in flames by aerospace engineers I shared office space with. Luckily, my curious nature has made me resilient enough to actually enjoy being shown the truth. Some of my seat-of-the-pants assumptions have turned out to have a basis in engineering fact, although I’d never have been able to verbalize the technical explanations. Still, some preconceptions remain, and nag at me to question my own collection of myths.
Here are some of the things I’ve been thinking about:
1. Does overall string length affect tension?
2. Does string tension really affect tone?
3. Is sustain hampered by pickup magnets?
I’m not going to answer all these questions today, and I may never completely solve any of this stuff to anyone’s satisfaction, but over the next few months, I’ll be building test rigs and conducting experiments for our collective amusement, and maybe shining a light on why things are the way they are. To be sure, I’ll be calling upon input from people whose expertise far exceeds mine.
In the early 1970s, I was involved with the construction of a custom instrument for King Crimson/Bad Company bassist Boz Burrell. Primarily known for his use of a fretless Ampeg bass, Burrell commissioned a similar fretted version with a few stipulations. His contention was that the entire length of the string contributed to the tension and timbre of an instrument. This came from his experience with upright basses. Therefore, he suggested that the distance between the bridge and tailpiece should be as long as possible.
It was partially from this conversation that I formed my notion that total string length determined tension. This hypothesis was also fueled by rumors that Hendrix’s reversed-headstock Strats provided him with distinctive tone. Jazz guitars with long string lengths between bridge and trapeze tailpieces also seemed to have a more strident feel and sound. Could the string-length theory be responsible? After many years of believing so, I wanted to find out. So, I first zeroed in on the question of tension.
I called Mike Connolly, a veteran of string manufacturing with Dean Markley and now owner of MJC Ironworks. “I’d never actually thought about it in those terms,” he offered. “It’s my feeling that you might have something there.” At that point he launched into something about Young’s modulus, which defines the mechanical properties of materials under compression or extension. It felt like my first day in calculus class, which I dropped. Connolly reckoned that the numbers might not support my conclusion, but he agreed there might be perceived changes in feel due to sideways resistance, which would be felt either plucking or bending strings. Although it wasn’t a definitive answer, I was getting closer.
Next, I spoke with Collin Olson, a materials engineer in product development at D’Addario. Olson was just the kind of guy to crack the code, but, again, I was in over my head. I tried to hang on as he called out first order effects and mass/unit to given tension parameters. I was starting to feel like a drowning swimmer as he launched into standing wave theory when I hit pay dirt. “There’s definitely a lot of confusion out there,” he acknowledged. “I think it comes down to the difference between actual tension and perceived tension.” When I mentioned the off-axis movement that fretting or plucking produced, Olson agreed that elasticity might come into play—which is to say that sideways stretching of the string may be affected without showing an increase in static tension.
To find out, I built a better mousetrap. My tension rig (Photo 1) was constructed from aluminum with plates to mount a precision tension gauge. The distance between the “bridge” and the “nut” was 25.5", while the tuner placements replicated the extreme ends of a Fender-style headstock: 4.75", beginning at 1.5" from the nut. Using a typical low-E (.046") string tuned to pitch, I measured the tension over the entire length at both points. Guess what? The results were exactly the same.
It’s no secret that the guitar universe is filled with a lot of mythology, and not a lot of science, so sometimes we get a wake-up call when presented with the facts. Of course, we all can choose to ignore the facts and just keep on believing what we want to believe. My long-held belief that overall string length changed tension at a given pitch was based on intuition, hearsay, and incidental evidence, rather than a plan or method. And I was wrong. But, the story isn’t over. Is there a perceived difference created by increased resistance to bending? Does that affect tone? I’ll have to test those next.