Sounds like a grounding issue with the power to the speakers, can you try a different outlet and see if that changes things. Maybe a different power supply to the monitors.
Help! I have a pair of Yamaha H8 monitor speakers. They have started to produce a loud humming noise when connected to my controller (DDJ 400). I first thought that it was a connection issue between the controller and the monitor, but it seems like it is the cable itself. I have tried different cables, but the problem persists. When I touch the end that plugs into the controller to where it plugs into the monitor (metal part), the noise goes away, but so does the sound. Any idea how to fix this issue? If I plug in with different cables and remove the other cable entirely, the sound is tinny.