Speaker wire

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RCA speaker wire
RCA speaker wire
stripped speaker wires
stripped speaker wires

Speaker wire is used to make the electrical connection between loudspeakers and audio amplifiers. Modern speaker wire consists of two electrical conductors individually insulated by plastic. The two wires are electrically identical, but are marked (eg a ridge on the insulation of one wire, color of one wire, a thread in one wire, etc) to allow convenient polarization connection.

Some historic designs also featured another pair of wires for electrical power for an electromagnet in the loudspeaker. At least one such speaker design is still in production (in France), but essentially all speakers manufactured now use permanent magnets, which displaced field electromagnet speakers over half a century ago.

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 much advertising claims on these points has also been a matter of much debate.

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[edit] Explanation

Speaker wire, like any other linear electrical component, has three parameters which determine its performance: resistance, capacitance, and inductance. Robustness is also significant in some applications. If a perfect wire were possible it would have no resistance, no capacitance, and no inductance. The shorter a wire is, the closer it comes to being perfect as resistance increases with length in all conductors. Resistance can in a minority of cases have some effect on speaker wire performance, whereas capacitative and inductive characteristics of speaker wire are vanishingly small relative to the loudspeaker itself.

The quality of construction is often chosen for price, aesthetic purposes and convenience. Stranded wire is more flexible than solid wire, and suitable for movable equipment. For a wire that will be exposed, often in a home, (rather than run within walls, under floor coverings, or behind molding), appearance may be a benefit, a wholly subjective one, but is irrelevant for electrical characteristics. Better purification of oxidizing materials such as copper is claimed to result in more consistent conductive properties throughout the length of the wire, but this is a non-issue in terms of its effects on sound quality. Better jacketing may be thicker or tougher, less likely to tangle and easier to pull through a group of other wires, or incorporate a number of shielding techniques for non-domestic uses.

Even with a poor wire, an audible degradation of sound may not exist. Many supposedly audible differences in speaker wire can be attributed to listener bias or the placebo effect. Listener bias is helped in no small part by the popular practice of lead manufacturers making claims about their products with either no valid engineering or scientific basis, or of no real world significance. Many manufacturers catering to audiophiles (as well as those available in less expensive retail locations) also make poetic, if unmeasurable, claims about this wire sounding open, dynamic, or smooth. To justify the claims, many rely on electrical properties such as skin effect, characteristic impedance of the cable, or resonance, which are generally little understood by consumers. None of these have any measurable effect at audio frequencies, though each matters at radio frequencies [1].

[edit] Resistance

Resistance is by far the most important specification of speaker wire. Low resistance speaker wire allows more of the amplifier's power to energize the loudspeaker's voice coil. The shorter the cable and the greater its conductor cross-sectional area, the lower its resistance. However, real world speaker wire resistances have no detectable effect in standard domestic installations.

A speaker wire’s impedance takes into account the wire’s resistance, the wire’s path (coiled wire acts as an Inductor), the dielectric properties of local insulators. The latter two factors give the wire its frequency response. The lower the impedance of the speaker, the greater the significance of the resistance of the speaker wire will be. High power in car audio systems using 2 ohm speaker circuits require relatively thick cables.

[edit] Wire gauge

Thicker wires in a cable reduce resistance; insulation thickness or type has no effect. Counterintuitively, the gauge sizes in SWG (standard wire gauge) and AWG (American wire gauge) reduce as the wire gets larger. In the American wire gauge (AWG) system common in the US, an 8 gauge wire is thinner than a 4 gauge wire and thicker than a 16 gauge wire. Sizing in square millimeters is also common and less prone to confusion.

[edit] Wire material

Use of copper is more or less universal for speaker wire; it has low resistance and less cost compared to other suitable materials. Copper and aluminum both oxidize but the oxides of copper are conductive, those of aluminum are capacitative and insulating.

Silver has a slightly lower resistivity than copper, which allows a thinner wire to have the same resistance. Silver is expensive and so a thicker copper wire with the same resistance will cost considerably less. Like copper, silver also suffers from oxidation.

Gold has a higher resistivity than either copper or silver, but it does not oxidize, so can be used for wire end terminations. Suitably specified gold flashing for appropriate tasks has its uses, but in domestic use such flashing is not normally functional, for several reasons.

[edit] Capacitance and inductance

Speaker wire capacitance and inductance normally have no effect on audio quality, though extreme examples using unusual high impedance speakers and exceptionally long wire runs can show a small effect.

[edit] Terminations

Speaker wire terminations are optional and largely for convenience, as bare wire ends work just as well electrically, and may work better mechanically as adding a termination introduces another potential point of error in installation or of failure over time. The most common termination types are solder tinned wire ends; soldered or crimped pin or spade lugs; banana plugs; and 2 pin DIN plugs. Which type to use is determined by the connectors on the equipment at each end of the wire.

Some terminations are plated in gold, which is of no functional use on consumer equipment speaker lines, but markets equipment to end users unfamiliar with the relevant principles. Gold plated connectors can resist corrosion better than some other materials, in a moist environment.

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). Use of larger 12awg wires may require trimming some 30% of the strands at the wire end (in common stranded wiring). This makes no significant change in the electrical characteristics of the wire.

There are also several types of proprietary connectors, though these are largely on all-in-one entertainment centers and bookshelf stereo systems.

In recent years, the Neutrik Speakon connector is appearing more and more on pro audio equipment. One reason is simple: in many European Countries the banana plug can fit into 230v mains sockets. A mistake will damage equipment and could possibly injure or kill someone as well. Recent EU regulations prohibit banana plugs in non-AC equipment, unless equipped with a safety pin mechanism preventing insertion into a wall outlet; there is such a connector available (from WBT Connectors) but it is not widely used.

Additionally, the Neutrik Speakon connector twists to lock in place, preventing one cause of intermittent failure, and accidental disconnection common in well used banana plug connections. The Speakon also carries more current than a heavy duty 15A 1/4" phone plugs (originally used in the telephone industry) and doesn't short two conductors together at insertion.

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