PS Audio Co-Founder and Superphon and Supermods founder Stan Warren is a big believer in freezing speaker cables and interconnects. He also freezes a lot of the circuits he modifies currently. Stan uses dry ice. He has found it is cold enough (minus 100 degrees fairenheit) to do the trick. Therefore you can buy some dry ice and do it yourself. He recommends doing in stages (ie, refrigerator, freezer, dry ice, back to freezer, refrigerator, room temperature), so not the shock the metal.
Mike Vansevers who makes power cords and conditioners, cyrogenically treats the input plugs on his reference level AC conditioners.