Universal factors govern the wires chosen for any given application, whether selecting speaker wire to rewire your speakers' internal connections or making the link between amplifier and speaker. Proper gauge, shielding and terminations universally affect performance, longevity and trouble-free amplifier operation. Speaker wires need not be expensive at their most basic, but that doesn't mean the cheapest option is the wisest when making wire-purchasing choices.
1Gauge versus Distance: Speakers perform their best when properly wired using the correct gauge of speaker wire. Outside of esoteric reasons like unique manufacturer performance claims, specialized cosmetics or additions such as batteries or frequency network boxes, speaker wires are chosen based on gauge. In electrical terms, resistance is the factor that measures how much a wire impedes an electrical signal. The longer the wire, the more resistance builds. Resistance on a wire that is too small, too long or a combination of the two results in thin sound, lacking in bass and impact. At distances of 50 feet or less, 16-gauge speaker wire is electrically sound, preventing these issues. Beyond 50 feet, 14- or 12-gauge wire should be selected to ensure maximum signal transfer. Internal speaker wiring is normally no more than a few inches, so smaller, 18-gauge wires are electrically acceptable when choosing these leads.
2Shielding: Speaker wire in most conventional applications does not require shielding. Except for extreme situations such as a wire improperly installed too close to an AC wire or unshielded electrical device, the amplified signal on a speaker wire is far stronger than any radiated interference may provide. The exception to this are scenarios in which long runs of speaker wire are coiled, effectively forming an AM antenna. CL-rated speaker wires designed to route through walls are sometimes protected with a thin foil shield, mitigating the effects of close proximity to AC wires and outlets. Speaker wire terminal wires leading to internal components such as the crossover and individual drivers do not require shielding, unless the speaker is internally amplified. The added electrical components inside such speakers may present an opportunity for interference.
3Different Metals: The vast majority of speaker wire uses reduced-oxygen copper, reducing the likelihood of oxidation in indoor environments without excessive humidity. However, more esoteric or premium designs sometimes feature silver, designed to improve high frequency performance. You may choose higher-conductivity silver for internal wiring, teaming with premium crossover components to ensure the cleanest possible signal. Although pure silver speaker wires are expensive and rare, it is not uncommon to see copper wires clad in silver, leveraging the tendency of high frequencies to travel along the outside of the cable. Aluminum is also used in some wires, but features reduced conductivity as compared to conventional copper wiring. Copper or silver should be used inside a speaker to prevent the need to use unnecessarily large wires to maintain proper conductivity.
4Inductance, Impedance and Capacitance: Inductance, impedance and capacitance cannot be ignored when discussing any electrical connection. In the audio realm, these three factors combine to affect audio performance and amplifier stability. Purposeful balancing of these electrical traits can help create a specific target sound, such as one with, for example, a bass-heavy or a bright tone. Inductance is determined by the distance between the positive and negative leads in the speaker wire. In most cases, this is too small to be a factor. Impedance in a speaker wire is usually kept low to prevent amplifier oscillations that damage speakers and the amplifiers themselves. High impedance speaker wires are deliberately designed to alter the sound of your system, effectively becoming passive tone controls. In most cases, bass is subjectively increased but under less control, resulting in a "flabby" sound. Capacitance is a factor based on the proximity between the two conductors and a third conductive material, such as an AC power wire or metal stud. Conductor spacing that decreases inductance increases capacitance, but most speaker wires are built competently enough to mitigate both issues effectively. Remember that esoteric and therefore expensive designs often exploit these factors to deliberately alter the sound of your system. In many cases, any change is seen as an improvement, but may be less accurate in relation to the source material on your CDs or Blu-ray discs.