CAR SUB / SM SERIES SM sub’s built with tripe high flux ferrite motor. The motor utilizes Y35. As you can see from the photo on the T-yoke, this special shape increase transfer heat area, this design make the speaker more efficiency. SM15 | 15" 7000 Watt Max Power Car SubwooferSM18 | 18" 7000 Watt Max Power Car Subwoofer