You will often see impedance mentioned when researching speakers, and amplifiers. Impedance is basically resistance measured at a given frequency, given as a value in Ohms (Ω), and is incredibly important to consider when setting up an audio system as it determines the ‘load’ placed on an amplifier by the speakers.
For example, let’s say we have an amplifier that is rated to deliver 100W into an 8Ω speaker load. If we were to then use speakers with an impedance of 4Ω with the same amplifier, the amp would then need to supply 200W as a halving of the impedance results in a doubling of the required power due to the reduction of the load on the amplifier.
In a situation such as this, if the amp can’t supply the required power for a lower impedance, then it can result in overheating, and damage to the amplifier and speakers.
For this reason, it is important to pay attention to amplifier specifications, and suggested impedance ratings.