Yes it is possible to pick up radio interference through speaker cables but you have to be near some very strong fields.
Please note this article I wrote some six years ago:
http://www.audioholics.com/education/cables/bulletproofing-your-system-from-interference
Please also note that RF really does not "sneak" it's way in to an amplifier through the feedback loop as the feedback is always referenced to the input.
Regards;
Dan Banquer
Hi Dan and all Audio Circle members.
I've read tons of articles on interconnects and cables and I came up to this conclusion:
(This is my conclusion, it's well suited for me, if it is for you: Good, if its not good for you, then find your own way of solving your problem.)
One easy way to reduce to almost zero all kind of interferences and not degrade sound quality by too high inductance and capacitance is to keep every wires as short as possible.
Interconnects: Less than 24 to 36"
Speakers cables: Less than 10 feet.
When you need to go more than that, then it becomes important to get better, more expensive wires or take another approach.
My opinion, no need to agree with me and tell me I know nothing or that I support mister so and so...
Guy 13