It is important to match the speaker load with your amplifier’s output impedance for a couple of reasons. One reason is that you will get maximum transfer of power. The other reason is that you can sometimes approach dangerous conditions for your amp if you have the incorrect load. When in doubt, it is safer to go higher in impedance to help protect the amplifier. The manner in which your speakers (in a multi-speaker system) are wired together determines the overall impedance.

Wiring Configuration for 2 Speakers in Parallel
Wiring two speakers in parallel

Two 4 ohm speakers = 2 ohm load

Two 8 ohm speakers = 4 ohm load

Two 16 ohm speakers = 8 ohm load
Wiring Configuration for 2 Speakers in Series

Wiring two speakers in series Two 2 ohm speakers = 4 ohm load

Two 4 ohm speakers = 8 ohm load

Two 8 ohm speakers = 16 ohm load
Wiring Configuration for 4 Speakers in Parallel
Wiring four speakers in parallel

 Four 8 ohm speakers = 2 ohm load

Four 16 ohm speakers = 4 ohm load

Four 32 ohm speakers = 8 ohm load
Wiring Configuration for 4 Speakers in Series/Parallel
Wiring four speakers in series/parallel

 Four 4 ohm speakers = 4 ohm load

Four 8 ohm speakers = 8 ohm load

Four 16 ohm speakers = 16 ohm load