Normally, you can unscrew the speakers from the front of the cabinet. I have not tried this, but I wonder if you can reach in and arrange some heavy duty aluminum foil on the side of the cabinet facing the tv. It would probably help if the foil could be sandwiched between the insulation inside the cabinet -- otherwise you might get some noticeable resonanance. This would be a cheap and easy experiment. Another plan of action would be to contact Paradigm to see if they have an aftermarket shield that can be applied to the speakers once you remove them from the box (there are normally four or more screws holding in the speakers -- you probably don't have to worry about the tweeter since that magnet is so small). I've found the customer service at Paradigm to be exceptional. Good luck.
