WOW, I remember this sub 1st apearance, back in 1989. This is the first subwoofer that I saw with a massive design. To my knowledge, Its a rare item in the car audio world, I've only seen one set-up of 4 10s and I dont recall how they sounded though. Its "magnetic voice coil design" called Differential Drive Design (DDD) motor, which at extreemly high-power each coil will enter the other coil's magnetic gap causing a "magnetic braking" which will slow the cone's motion and prevent damage from over-excursion ( as seen on my post "they're not bad after all" on the 12w6v2), with fins design to dissipate heat from voice coils and Kevlar-impregnated paper woofer cone. The're gotta be something about those paper cones.//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif