It would be nice to know what kind of frequencies he is on....if he is on HF or VHF, especially.
I've heard lots of complaints concerning subwoofers, due to the fact that most are just a plastic or wooden box, with a circuit board for the electronics (amp, crossover, etc) sitting inside it...basically, "floating" in the electrical field, with no shielding (visualize it like, everything that's non-metal is clear plastic).
If it's coming in via HF band (below 30, or 50, MHz or so), winding the power cord and the audio cables, individually, through a toroid or ferrite core that's the correct chemical "mix" for that range of frequencies might do the trick. That's assuming the cable(s) are acting as an antenna to his signals.
If the interference is coupled directly to the circuits through the air, then the best bet might be to try and re-position the sub (maybe to the other side of the screen, a few feet away) , or see if you can block the signal with a piece of metal or foil...at least temporarily, as an experiment. Sometimes, a roll of metal "window screen" and some clips to keep the edges folded together, can be a great troubleshooting tool.
One thing I'd wonder though....when you disconnect all the cables (power and audio) from the subwoofer, does the TV interference go away? If so, it's just being channeled to the TV and other equipment, via the wires from the sub. So, fixing the subwoofer end of things would do it.
If I remember correctly (I'm at work, my stuff is at home), something like the FT-240-J works with most power cords, and the FT-140A-J will handle a couple of audio cables with RCA plugs on them, here:https://www.amidoncorp.com/items/21
Look at the drawing of the "Choke Balun" here, for how to wrap the cables:http://www.ce3rkw.net23.net/antena_vertical_hf.htm
The J-series core material is good over much of the HF Ham Radio band, up to about 20 MHz. If he's a CB'er, he's on 28-29 MHz, and you'd need something higher, like the 43-series. You'll find that many of the readily-available ferrites, from places like Radio Shack, are that material, and start at about 20-25 MHz, soaking up interference to about 250 MHz, which includes the VHF Ham Bands like "2-meters".
Also, keep the lengths of excess cable to a minimum. Either use shorter ones, or at least coil up the extra length in a small bundle.
BTW, if the interference is coming in via the TV antenna cable (which would be proven by disconnecting all the other cables from it, except power and the antenna), looping the antenna cable through a core 2 or 3 turns/passes, right near where it plugs in to the TV, may help. That keeps his radio's RF off the shell of the tuner module, and off the TV's circuit board. A core on the power cord is likely to be necessary, too.