I have a pair of KRK RP6G2 for my bedroom studio.
Tonight I noticed that both the speakers have a hiss coming through, when they're turned on, but there's no audio cable plugged in.
What's causing this, and what can I do to resolve it?
Depending on how loud it is, this could just be normal. My Genelec speakers do the same, but it is only very low, so you need to be fairly close to really hear it. It is because they are active.
Is the hiss you hear much louder than that? Does it actually affect monitoring? If so you may have something faulty, but I expect this is normal behavior. I've only used the G2s in classroom situation and don't remember any unusually loud hiss from them.
I think they have a level control of some sort too. Does that affect how loud the hiss is?