There is a product that allows you to place a perimeter around the speakers (or any other object), the cat(s) wear a special collar, and if they approach the speakers, they hear a tone that increase in pitch & frequency the closer they get, if they cross the perimeter, they get a shock. You can vary the shock intensity with a variety of plug in resistors. You should be able to find these at major pet discount warehouses, Google searching, etc.
You can also make a perimeter of upside down mouse traps that will scare them from the speakers (but you need to keep resetting them as snapped in order to be effective).
You can also make a perimeter of upside down mouse traps that will scare them from the speakers (but you need to keep resetting them as snapped in order to be effective).