MATCH UP W8BMW-S Two 8" shallow-mount component subwoofers — designed to fit select BMW vehicles with under-seat subs at Crutchfield
Do You Need a Subwoofer to Mix Music?
Gately Audio - 2 12” subs up port back 4.75cf
The Five Cs of Subwoofer Setup | Wirecutter
Amazon.com: Polk Audio HTS 10 Powered Subwoofer with Power Port Technology | 10” Woofer, up to 200W Amp | For the Ultimate Home Theater Experience | Modern Sub that Fits in any