A Technical Introduction to Audio Cables

What is so important about cables anyway?

One of the most common questions asked by consumers faced with purchasing cables for their audio or Home theater system is, "What is so important about cables anyway?" They can cost as much or more than some of the hardware in the system and to many it is difficult to understand why wire isn't just wire.

To begin to understand how audio cables work, we have to start with the two fundamentally different types of audio cables you are likely to have in your system. The first type of cable is called an interconnect, which is used to connect various components together (such as a CD player to a receiver). The second type of cable is called the loudspeaker cable (this is the wire going from the receiver or amplifier to the speakers). It is important to realize that both types of cables are carrying the same information, just with different amounts of energy.

Interconnects carry a signal with very little energy. These cables only need just enough energy to convey the information from the source, for example a CD player, to the amplifier. The low energy requirement means that the signal in interconnects has very little current (usually in the range of thousandths of an amp).

Loudspeaker cables on the other hand, carry a large amount of energy. All of the energy required to move the speaker cones and make sound must come through the loudspeaker cables. Because of the high-energy requirement in these cables the current is relatively high (currents can reach 10 amps or more).

The very basic reason why audio cables are important is because they change the signal going through them. There are two different, fundamental ways that an audio cable can change the signal. The cable itself can change the signal, or the cable can allow outside sources of energy to change the signal.

In order to understand how these two situations can occur, some basic background electrical knowledge is needed.

Signals in all types of wires are conveyed by the combination of voltage and current. Every signal has some amount of voltage and some amount of current. The larger the difference in voltage between two places, say the beginning and the end of a cable, the larger the amount of current, and vice-versa. The direct analogy to voltage and current is the flow of water through a hose. The amount of water flowing through the hose is analogous to current. The water pressure in the hose is analogous to voltage. The higher the amount of water pressure, the more water will flow through the hose. The higher the amount of voltage, the more current will flow through the wire.

Every cable has a set of electrical properties that can be measured using standard electrical testing equipment. The three most basic properties are resistance, capacitance and inductance. While a detailed description of these three different electrical properties is outside the scope of this article, a basic description of the relevant effects of these three properties can be given.

- Resistance opposes current. The higher the resistance the greater the amount of energy that is removed from the current and turned into heat.

- Capacitance opposes changes in voltage. If a voltage is increasing, capacitance will cause the voltage to increase more slowly. If a voltage is decreasing, capacitance will cause the voltage to decrease more slowly.

- Inductance opposes changes in current. If current is increasing, inductance will cause the current to increase more slowly. If current is decreasing, inductance will causethe current to decrease more slowly.

The final piece of background knowledge that is needed for this article is what the audio signal looks like. If one were to take the speaker cover off a speaker to look at the speaker cone while music is playing, you would see that it is moving back and forth. In order to move the speaker cone back and forth, the electrical signal must push and then pull the cone in rapid and repeating fashion. This is accomplished by having an Alternating Current, or AC.

Alternating Current simply means that the voltage oscillates between positive and negative. Because the voltage drives the current, this means that the current also goes positive and negative. In other words, the cu