Dayton Audio ND90-4 3-1/2" Aluminum Cone Full-Range Neo Driver 4 Ohm Full-range 80 Hz to 15 kHz performance Rubber-edged aluminum alloy cone Large excursion capability-4 mm Xmax, 20 mm peak Self-shielded Neo-Balanced motor structure 3/4&quot; 4-layer underhung voice coil with polyimide former