The speaker cable is the wire or cable used to connect the amplifier to the loudspeaker system.

Like all cables it has three main properties: capacitance, inductance and resistance. As a result of the environment in which speaker csable operates it is the resistance that is the most important. This is brought about by the relatively low frequencies used and the system impedance. Most speaker systems have an impedance of anywhere between around three or four ohms up to around 15 ohms. Today most loudspeaker systems have an impedance between four and eight ohms.

As the resistance rises it starts to affect the system performance. Obviously there can be a reduction in the drive current to the loudspeaker as the voltage across the speaker cable increases. The other issue is that the back EMF created by the loudspeaker needs to have a low impedance source against which to work. As the source impedance rises, so the back EMF is absorbed less. This affects the performance of the loudspeaker, particularly in the bass region where the bass may not be as pronounced and it may sound less natural.

Typically the effects of the speaker cable start to become noticeable when the resistance of the cable reaches about 5% of the speaker impedance. Some may even say it needs to be less.