Powerful speaker magnets really play havoc with compasses?unless they’re Ultra-Low Magnetic Field speakers. Because their cancelling magnets and shielded enclosures significantly reduce magnetic flux, you don’t have to mount them 5' from compasses and autopilots like other systems. 4000 series speakers combine a mid-range polypropylene cone with a 1" mylar tweeter for full-range frequency response. 80 watts peak power per pair. 4-ohm impedance.