Occasionally lost in the excitement of purchasing new home theater or stereo speakers is the reality that speaker wire is not included. The extensive options and claims made by speaker wire manufacturers potentially cloud the issue, making what should be a simple task more complex. Although sound quality differences between various iterations of speaker wire are largely subjective, core elements such as using the proper gauge wire, terminating the cable, and metal materials used in the construction all have an impact on performance.
Proper Gauge (AWG)
The primary element of a speaker wire's effect on audio performance concerns electrical resistance, which is the degree to which the metal in the wire interferes with the signal. In the case of speaker wire, too much resistance is a result of using wires that are too small for the distance the signal travels, the speaker's electrical impedance or the amount of power produced by the amplifier. For example, while 16-gauge speaker wire is perfectly acceptable under 50 feet with a 100-watt amplifier using an 8-Ohm speaker, that distance is halved when using a 4-Ohm speaker, or you need to move up to 14- or 12-gauge wire. The impedance of a speaker is a measure of how much restriction the voice coil places on electrical current as it passes through, with lower numbers indicating increased impedance. Most home speakers are relatively easy-to-drive 8- or 6-Ohm loads, while the majority of car audio speakers are 4 Ohms or below.
By far the most common material used to construct speaker wire is oxygen-free copper. The less oxygen is present, the "purer" the wire is judged to be. The purer the copper, the less likely it is to oxidize under normal circumstances, although environmental factors such as humidity affect this metric. Increasing the cost of speaker wire fairly significantly is the use of pure silver. This metal has a slightly better degree of conductivity, although you will have to determine how much of an improvement is worth the increased cost. To keep costs down while maintaining most of the effects of silver wire, a silver microplate is applied over conventional oxygen-free copper. This is effective since most of the improvements seen by silver wires happen at high frequencies, which tend to travel toward the outside of the wire. You may also encounter aluminum wire with a copper plating, but these are relatively rare and only found in more esoteric wiring to affect the sound. Normally, you need a one-gauge increase with aluminum wire to match the conductivity of copper. For example, a 16-gauge copper wire requires a 14- or 12-gauge aluminum wire to meet the same standards.
Shielding and Interference
Speaker wire is relatively immune to electromagnetic and radio frequency interference, so the need for shielding is almost non-existent. This is due to the fact that the signals on the speaker wire are amplified to a much greater degree than any potential interference, cancelling out noise. However, you may discover that some CL-rated, in-wall speaker wires are shielded, since on occasion a wire may pass too close to an AC wire or other electrical device that emits significant interference. Although speaker and signal wires should always cross AC wiring at a 90-degree angle to cancel noise, it's not always evident where AC wires really are in a finished wall. Should an unshielded in-wall speaker cable pass too close to an AC line, hum usually appears at the connected speakers.
A method of decreasing oxygen penetration while improving looks and ease of connectivity to a speaker or amplifier is to terminate the wire. Found in crimp or reusable screw-on versions, these terminations include banana plug, braided wire, pins or spades. The one you choose is mainly based on preference or the capabilities of the equipment. For example, a standard five-way binding post on a speaker or amplifier has a hole at the center, making banana plug insertion easy and fast. Alternately, spades may be used tightened under the rotating binding post, or braided or solid pins deployed when spring terminals are present. In each case, a more secure connection is obtained while potentially increasing the life of the wire.
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