This is a problem that may likely require the skills of an experienced repair tech. If you are not comfortable working on electronic devices, find someone who can do it for you.
UNPLUG YOUR SPEAKER BEFORE INSPECTING A PROBLEM.The first place I would look is the
FUSE. Each of the speakers contains a power amplifier and each has a fuse that will blow to protect the power transformer, circuit and speakers. If you are getting NO POWER at all to the speaker, check the fuse first. It is located on the AC plug circuit board.
You can download the
PDF for the HS series here. It includes all of the circuit diagrams, parts lists and close-up photos of the parts.
If the fuse is not the problem, the speaker's power amp has suffered more sever damage and you would certainly need an experienced technician to diagnose the problem.
Good luck!