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Electronics component

Speaker wire is used to make the electrical connection between loudspeakers and audio amplifiers. Modern speaker wire consists of two or more electrical conductors individually insulated by plastic (such as PVC, PE or Teflon) or, less commonly, rubber. The two wires are electrically identical, but are marked to identify the correct audio signal polarity. Most commonly, speaker wire comes in the form of zip cord. The effect of speaker wire upon the signal it carries has been a much debated topic in the audiophile and high fidelity worlds. The accuracy of many advertising claims on these points has been disputed by expert engineers who emphasize that simple electrical resistance is by far the most important characteristic of speaker wire.

Early speaker cable was typically stranded copper wire, insulated with cloth tape, waxed paper or rubber. For portable applications, common lampcord was used, twisted in pairs for mechanical reasons. Cables were often soldered in place at one end. Other terminations were binding posts, terminal strips, and spade lugs for crimp connections. Two conductor quarter inch tip sleeve phone jacks came into use in the 1920s and '30s as convenient terminations. Some early speaker cable designs featured another pair of wires for rectified direct current to supply electrical power for an electromagnet in the loudspeaker. Essentially all speakers manufactured now use permanent magnets, a practice which displaced field electromagnet speakers in the 1940s and 1950s.

Speaker wire is a passive electrical component described by its electrical impedance, Z. The impedance can be broken up into three properties which determine its performance: the real part of the impedance, or the resistance, and the imaginary component of the impedance: capacitance or inductance. The ideal speaker wire has no resistance, capacitance, or inductance. The shorter and thicker a wire is, the lower is its resistance, as the electrical resistance of a wire is proportional to its length and inversely proportional to its cross sectional area (except superconductors). The wire's resistance has the greatest effect on its performance. For aluminum or copper clad aluminum wire, 14 gauge or heavier cable is needed to support this claim due to higher resistivity.

Use of copper or copper clad aluminum (CCA) is more or less universal for speaker wire. Copper has low resistance compared to most other suitable materials. CCA is cheaper and lighter, at the expense of somewhat higher resistance (about the same as copper two AWG numbers up). Copper and aluminum both oxidize, but oxides of copper are conductive, while those of aluminum are insulating. Also offered is Oxygen free Copper (OFC), sold in several grades. The various grades are marketed as having better conductivity and durability, but they have no significant benefit in audio applications. so a run of up to about 10 feet (20 total feet of conductor) will have less than 1% inductive loss in the audible range (10 ft * 0.2 μH/ft = 2.0 μH, which is at or below the proximate threshold of 2 μH given above). Some premium speaker cables have lower inductance at the cost of higher capacitance; 0.02 0.05μH/ft is typical, which at the worst end means that a run of up to about 40 feet will have less than 1% inductive loss (40 ft * 0.05 μH/ft = 2.0& μH).

Skin effect in audio cables is the tendency for high frequency signals to travel more on the surface than in the center of the conductor, as if the conductor were a hollow metal pipe. Regardless of marketing claims, skin effect has an inaudible and therefore negligible effect in typical inexpensive cables for loudspeaker or other audio signals. The increase in resistance for signals at 20,000 Hz is under 3%, in the range of a few milliohms for the common home stereo system; an insignificant and inaudible degree of attenuation.

Speaker wire terminations facilitate the connection of speaker wire to both amplifiers and loudspeakers. Examples of termination include soldered or crimped pin or spade lugs, banana plugs, and 2 pin DIN connectors. A commercial speaker wire connector from Neutrik (viz, Speakon) has some advantages: it does not easily pull free, does not make partial contact when making or breaking (1/4 plugs and sockets inherently do so) and offers multi circuits in some versions. The type of actual electrical contact (ie, termination) is determined by the connectors on the equipment at each end of the wire. Some terminations are gold plated. Many speakers and electronics have flexible five way binding posts that can be screwed down or held down by a spring to accept bare or soldered wire and pins or springy banana plugs (through a hole in the outward facing side of the post).

There is debate among audiophiles surrounding the impact that high end cables have on audio systems with audibility of the changes central to the discussion. While some speaker wire marketers claim audible improvement with design or exotic materials, skeptics say that a few meters of speaker wire from the power amplifier to the binding posts of the loudspeakers cannot possibly have much influence because of the greater influence from complex crossover circuits found in most speakers and particularly from the speaker driver voice coils that have several meters of very thin wire. To justify claims of enhanced audio quality, many marketers of high end speaker cables cite electrical properties such as skin effect, characteristic impedance or resonance; properties which are generally little understood by consumers. None of these have any measurable effect at audio frequencies, though each matters at radio frequencies. Industry experts have disproven the higher quality claims through measurement of the sound systems and through double blind ABX tests of listeners. There is however agreement that the overall resistance of the speaker wire should not be too high. An accepted guideline is that the wire resistance should not exceed 5% of the entire circuit. For a given material, resistance is a function of length and thickness (specifically of the ratio of length to cross sectional area). For this reason, lower impedance speakers require lower resistance speaker wire. Once the 5% guideline is met, thicker wire will not provide any improvement. Roger Russell – a former engineer and speaker designer for McIntosh Labs – details how expensive speaker wire brand marketing misinforms consumers in his online essay called Speaker Wire – A History. He writes, "The industry has now reached the point where [wire] resistance and listening quality are not the issues any more, although listening claims may still be made The strategy in selling these products is, in part, to appeal to those who are looking to impress others with something unique and expensive."