Polk Audio AA2691-A MM691 6x9 3-Way Speaker Neodymium Magnets a rare earth metal offering exceptional strength to performance ratio Carbon Composite Basket based on the spokes of a wheel is lightweight Klippel Optimized Components using a state-of-the-art Klippel Distortion Analyzer Woven Glass Composite Cones feature tremendous stiffness-tomass ratio. Lower mass means faster transients and finer detail. Large-Diameter Voice Coils (30mm) in drivers increase reliability and power handling capacity.