I had the same problem some time ago with my Velodyne Subs - caused by my Cable TV Box - Shaw as well. This is a common problem & Shaw normally will not acknowledge it.

I made a jumper cable of zip wire with alligator clips on each end. Attached one clip to the outside barrel of an audio jack on the sub & did the same with the other end on the TV. Some experimenting was required to find out what connection worked best, but in the end the hum was gone.

When I replaced the Velos with my EP800s the hum was back but screwing 'out' the chassis ground screw cured it...

TAM