Car wiring diagrams: Bmw Subwoofer Harness, wiring diagram, wire wiring harness, schematic circuit diagram, wiring diagran, wireing diagram, wirring diagram, wiring daigram, wiring diagrams. My BMW M Coupe Z Subwoofer Installation . My M Coupe came with the Top HiFi Carver system that is the first THX certified factory stereo from a European car .SubThump offers the best subwoofer boxes and enclosure for Car and Trucks online at very competitive prices. Visit our website and browse through our products..If your BMW Z does not have rollhoops it may be possible to retrofit them into your vehicle. BMW has an upgrade kit, but it can only be used on Zs built on or after .