The acoustic guitar strings
How are they made? How many types exist? Which one to choose?
Here we need some patience, as the strings topic is particularly complex and tricky, for many reasons. On the one hand, we must consider construction techniques, different materials employed, usable gauges. On the other hand, to choose the correct strings we must analyse subjective and objective factors like playing skills (sensitivity, strength, technique), musical genre, the features of the instrument used (the scale length, for instance) and of course the personal tastes of the musician. But one thing you can take for sure: strings are an essential component if not crucial for the “sound” of any musician.
Typology and construction
The strings for acoustic instruments are
called steel strings (made of steel), to distinguish
them from those used per the classic guitar (nylon
strings). They are further divided into
two types: wound and plain strings. The wound strings (D, A,
E low) have metal windings around their core, that can have different shapes
(round, but more often hexagonal to maximize the stability of the windings).
The windings of the strings for electric instruments can be made of different
metals: bronze, bronzed steel, phosphor
bronze, silver, nickel.
The core/winding combinations create many different kind of strings. Some of the most common are:
The different type of windings influence the longevity of the string, the tone, the fret wear, and of course the final cost. For instance, the Nickel-wound strings offer low fret wear and are cheaper than the Bronze-wound, while the Silk&Steel feel softer and warmer thanks to the insertion of silk-like materials in the winding process.
There are some special treatments that
can increase the useful
life of the strings:
Cryogenic: using the possibilities of changing the alignment of the granular structure of metals (at about -190°) the strings become more resistant to oxidation and preserve their tone for a longer time.
Coated: ideal for the guitarists allergic to nickel, this further coating (polymeric based) extends the useful life of the strings. This coating wears off with intense and prolonged bendings and playing with a very aggressive strumming.
The different types of windings
From the construction point of view, there are 3 main types:
The core is the plain piece of steel that corresponds to the string itself in the case of plain strings, and has a round cross-section, while for wound strings the cross-section can have mainly two shapes: rounded or hexagonal.
with this solution the windings have a 100% contact with the core, the
string can vibrate more freely with a louder volume and a slower attack than a hex
core string. Nevertheless, the round shape causes an inferior stability of
windings, that sometime results in difficulties of intonation of the string. Moreover,
as the string vibrates in every direction and more freely, an higher action must
be set than a hex core string, to avoid noises from the string touching the
frets. For these reasons, together with higher manufacturing costs, many
manufacturers offer more and more hex core strings.
Hex core: the hexagonal shape of the
core offers more stability of windings, resulting in higher precision and
better intonation of the string. The string can vibrate less freely, with a
softer volume and a faster attack that allows for a lower action adjustment than
a round core string. Finally, the hex core string offers lower manufacturing
costs than a round core string.
Core to wrap
When buying strings of a different brand or different series from the same brand, sometimes you note that some strings (of the same gauge) are sonically different, and need different tension. Why? It is not a manufacturing fault, but an effect of the design and manufacturing of the string. As a matter of fact, also the core to wrap ratio has an effect on the physical and tonal characteristic of the string: a string whose winding wire diameter is larger than the core diameter will sound brighter and feel more flexible. On the contrary, if the core diameter is larger than the winding wire diameter, the string will show more sustain, volume, longevity and tension.
The tension created by a string set depends on the gauge of each string in the set. Thinner string gauge corresponds to less tension and consequently both the string action and the truss rod adjustment for a correct neck setup must be calibrated.
Generally speaking, acoustic guitar strings are heavier than those used for the electric guitar, and most common string sets commercially available are:
Buying single strings, we can create
personalized sets to meet our particular needs. On the acoustic guitar often
non-standard or open tunings are used, based on unusual intervals that can
require different gauges to handle the tensions that differ from the standard
tuning. Some example: a Plain Steel can
range from .07 to .24, a Bronze
80/20 from .20 to .59, a Phosphor Bronze
from .20 to .70.