Speaker wire
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 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.
[1] Some early speaker cable designs featured another pair of wires for rectified direct current to supply electrical power for an electromagnet in the loudspeaker.
[4] Speaker wires are selected based on price, quality of construction, aesthetic purpose, and convenience.
For a wire that will be exposed rather than run within walls, under floor coverings, or behind moldings (such as in a home), appearance may be a benefit, but it is irrelevant to electrical characteristics.
Better jacketing may be thicker or tougher, less chemically reactive with the conductor, less likely to tangle and easier to pull through a group of other wires, or may incorporate a number of shielding techniques for non-domestic uses.
The performance of a conductor such as speaker wire is therefore optimised by limiting its length and maximising its cross-sectional area.
[4] As speaker impedance drops, lower gauge (heavier) wire is needed to prevent degradation to damping factor – a measure of the amplifier's control over the position of the voice coil.
A common rule of thumb is that the resistance of the speaker wire should not exceed 5 percent of the rated impedance of the system.
The amount of attenuation can be calculated for any given frequency; the result is called the capacitive reactance, which is an effective resistance measured in ohms: where: This table shows the capacitive reactance in ohms (higher means lower loss) for various frequencies and capacitances; highlighted rows represent loss greater than 1% at 30 volts RMS: The voltage on a speaker wire depends on amplifier power; for a 100-watt-per-channel amplifier, the voltage will be about 30 volts RMS.
The following table shows the inductive reactance in ohms (lower means lower loss) for typical cable inductances at various audio frequencies; highlighted rows represent loss greater than 1% at 30 volts RMS: The voltage on a speaker wire depends on amplifier power; for a 100-watt-per-channel amplifier, the voltage will be about 30 volts RMS.
Ordinary lamp cord has an inductance of 0.1–0.2 μH/ft, likewise for shielded cord,[6] 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).
Skin effect is a significant problem at radio frequencies or over long distances such as miles and kilometers worth of high-tension electrical transmission lines, but not at audio frequencies carried over short distances measured in feet and meters.
[9] 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.
Examples of termination include soldered or crimped pin or spade lugs, banana plugs, and 2-pin DIN connectors.
The type of actual electrical contact (ie, termination) is determined by the connectors on the equipment at each end of the wire.
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.
[12] Industry experts have disproven the higher quality claims through measurement of the sound systems and through double-blind ABX tests of listeners.
[4] As well, the observed problems with speaker cable quality are largest for loudspeakers with passive cross-overs such as those typical of home stereos.
