Are you talking about a clearly audible (loud) hum, or is this something where you have to place your ear close to the speaker to hear? It's a rare system that doesn't produce some of the latter, but the former should be addressed. It's probably not hurting anything, but it certainly won't help your enjoyment of music. I suggest you check the REL connections at the amp and make sure your power cords aren't touching any signal carrying cables.
