These speakers are powered. There's an internal amplifier in the right speaker that powers it and the left speaker. The left speaker works fine when connected, but the right speaker still hums whether or not the left speaker is connected to it.
Swan M200 loud hum in right speaker
I just turned on my Swan M200 speakers today, and I noticed that a loud hum was coming out of my right speaker. I took off the cover, and it seems that the woofer was drawn inwards and stays in that position. When I turn it off, the woofer returns to equilibrium. It goes back inwards and starts humming when I turn it on again. The left speaker still works perfectly though. I've had these speakers for 2 years and this problem suddenly started today. I've already tried just using the right speaker without audio input on several power outlets and the same humming occurs. Any ideas what's wrong?