Forget about that concept of ohms, things are a bit different.

Loudspeakers - like everything - put up a certain resistance to electric current. This resistance is a property of the loudspeaker, not the amplifier. Traditionally,

*nominal *impedance (that's another, more general term for resistance) values for speakers are like 4, 8 or 16 ohms and none of these values equals the

*actual *resistance. In reality, a speaker's resistance is not constant. It varies a lot with frequency. The reason why a nominal impedance is provided by manufacturers is that not all amplifiers can handle all impedance values.

Amplifiers are usually designed to act as ideal voltage sources. That means, they try to provide the same voltage (for a given volume setting) regardless of the speaker's impedance. The trouble is: The lower the impedance, the higher the current the amp must provide. Cheap amps often cannot handle 4 ohms speakers (where the real impedance may dip even lower). In this case the voltage will no longer be constant but drop to a lower value. If an amplifier's power output into 4 ohms is noticeably less than twice the power into 8 ohms, this is what's happening.

As long as your speakers' impedance is not lower than what's in the amplifier's specs, you are safe.

This doesn't mean that the amplifier somehow provides 4 ohms (or 8 ohms). It just means that the amp can safely work into, say a 4 ohms load. In the end that's all you need to care about. A speaker rating of "4 - 8 ohms" is pretty much useless, these speakers should rather be rated 4 ohms. Too low impedance values can damage amplifiers, too high impedance values will just result in less power output, thus lower sound pressure level. That's pretty much all you need to know, apart from the fact that the WiiM Amp can safely drive 4 ohms speakers.

These are just some basics. Much more could be said about the topic of speaker impedance and amplifiers, but not in this posting.

Fun with maths:

Power = Voltage * Current = Voltage * (Voltage/Resistance) = Voltage²/Resistance

=>

max. Voltage = sqrt(max. Power * Resistance)

max. Voltage = sqrt(120 watts * 4 ohms) = 21,9 Volts

Cross check:

max. Power into 8 ohms = (21,9 Volts)²/8 ohms = 59,95 watts