INFINITY RS 2B CROSSOVER PROBLEM ??

Take the woofers out and get a look at the crossover inside the cabinet. Most likely problem is a broken wire/bad solder connection.
Those speakers are 20 years old.
I had a pair of RSIIa and rebuilt the crossovers on mine long ago.

Bill Legal at Millersound is an expert at all things to do with Infinity speakers. He may be able to repair them profesionally. If they are important enough to warrant the shipping and expense, but contact him to see if he can do anything in the first place.

Check whatever caps and resistors that are in series to those drivers.