HEX stands for High Excursion, these woofers come in 2500w and 5000w RMS models in 12, 15 and 18″ variants with enormous 220mm, 250mm and 280mm diameter magnets to deliver ground shaking bass. 3 and 4″ voice coils with a 75mm winding height allow the woofer to remain in total control electrically while moving on its 2 way linear movement of 70mm. Huge excursion and xmax means the woofer moves huge amounts of air delivering incredible bass and huge air pressure. The 10″ nomex spider keeps definitive control. Beautifully designed and ultra menacing.