Gauge (measurement of a string's diameter) - Is It Meaningful?

I often get calls from customers who are all caught up in the gauge of the string. This is perhaps because some of my customers come from an electric bass/guitar background, where gauge is the primary determinant of how "hard" or "easy" a string is to play. But really, for upright strings, gauge (sometimes) ain't nothin' but a number. DB strings have many characteristics that affect playability. Varied materials, radically different windings, etc - these factors are generally less prevalent in the "slab bass" world.

The point we have to address is that "tension," "flexibility," and "gauge" are terms that are often improperly used interchangeably... or altogether confused. They are not the same thing, but rather are each a distinct part of the whole that comprises playability (for each player.) Because of the many variables, it can get complicated to try to help folks find their perfect blend of all three.

A quick primer:
  • Put simply, Tension is the "weight" - in lbs. or kilograms - required to bring the string up to its required pitch at its designated scale length.
  • Flexibility is how easily the string can "bend" - a less scientific term, without practical measure for our purposes, it can vary based on the type of materials used in making the string. As a simple example, consider strings you may have in your overflow drawer; if you coiled them as tightly as you could without damaging them, a more flexible string could coil more tightly with less effort.
  • Gauge is the measurement of the string diameter - and it's almost meaningless for upright strings, as the different materials strings are made of change the other two properties and render gauge only a useful stat for your personal preferences (do you like beefy strings or skinny ones?) For instance, a Eurosonic Ultralight E string is 0.150, while a Thomastik Spirocore Stark E is 0.120. But that Eurosonic, because of the materials used, is MUCH lighter in tension, and probably more flexible, than the considerably "thinner" (lower gauge) Spirocore.
So for Double Bass strings, the gauge (diameter) of a string might actually the least important factor, IMHO. Here are a few things that are more important, not necessarily in descending order:
  1. Core Materials (macro) - the core of the string may be solid steel (for example, SuperSensitive Red Label), stranded steel (Corelli 370), synthetic (Evah Pirazzi), real gut (Oliv) or even some combination or other material. As you can imagine, this has a big effect on the tone, feel, playability, and tension of the string. A gut string sounds very different than a solid-core string, and it plays differently too - gut is more flexible and soft, while the solid core would feel more taut and stiff. So even at the same tension weight measurements, strings with different cores could feel "harder" or "softer" to play in direct comparison. And you can bet that they will have a big difference in gauge. But the gauge doesn't tell us much; in the case of a gut E versus a Spirocore E, for instance, the gut string would have a much larger gauge, but probably have a lighter tension and softer, more flexible feel.
  2. Core Materials (micro) - even within similar construction, there can be differences; for instance, if you compare Thomastik Superflexible strings to Corelli 370's, you'll find that they have very similar construction (flatwound, rope-core) - however, the Corellis have a considerably thinner gauge measurement. This is because Savarez (Corelli) strings use a special blend of steel that has more mass than the more "conventional" steel used by Thomastik; this allows a string that responds like a "heavier" string because it has equal mass (more or less) despite its smaller diameter.
  3. Additional layers - some strings add layers of silk, thread, or other materials as an intermediate winding - this may be to "damper" the response, shorten the sustain, darken the tone, etc. This adds "bulk" without necessarily adding a meaningful amount of tension.
  4. Outer winding - Windings can vary in material (silver, nickel, alloy, steel, nylon, perlon, etc.) and profile (wire, tapewound, flatwound, etc.) The varying materials, their thickness, as well as their winding design, can affect the playability/stiffness. For instance, a nylon tapewound string is not as "flexible" (imagine bending it like Superman bends a steel rod) as a wire-wound string. This, again, means that a string with nylon tape winding could be more "difficult" (stiff) to play than a wire wound string, even at the same tension (and gauge!)
All of that said... gauge can still be a factor in playability; the size of the string under the fingers can certainly affect how you approach playing the string. Some people prefer a big, beefy string that they can grab with their meathook fingers, others prefer a smaller gauged string and play with a more delicate, deft touch.

And certainly, tension is a very useful statistic to know - all else equal, a higher-tension string will be more physical to play than a lower tension string.

But as it pertains to the "feel" of a string, I just gently caution anyone against getting too focused on any one factor; as someone who pretty much talks about strings, all day, every day - I can tell you that it's a complex combination of factors that make the string "perfect" for a certain player (and hey, we didn't even get into timbre/tonal preferences here - that's the subject of a whole other conversation).