These Polk Audio DB571 High Performance Car Speakers feature Dynamic Balance® Driver Technology for pure, distortion free sound. It's an ultra-high-performance 5"x7" mid-woofer and 1-inch silk dome tweeter have a frequency response of 52Hz-22kHz and a sensitivity of 93db. Neodymium is a rare earth material used in all db driver magnets, excluding 461p, that are about 1/10 the weight of a comparable ceramic magnet and much more powerful. Marine Certified means the db571 is built tough to withstand the harshest environments on the water.