I am contemplating building some surround loudspeakers for a 5.1 system. The system will have a dedicated subwoofer. I am thinking of using full-range drivers for the surround speakers. How low should the frequency response extend for the surround speakers? How important is the off-axis frequency response, say above 5000 Hz? I plan on building each speaker as a dipole with switching to permit bipole and monopole function. Each driver will be in it's own compartment to prevent driver interation within each cabinet. Any other thoughts about this project would be most welcome.