BOSS Audio Systems BASS8 8 Inch Under Seat Powered Car Subwoofer – 800 High Output, Low Profile, Built In Amplifier, For Truck, Boxes and Enclosures, Remote Subwoofer Control
Focal Inside ISUB BMW4 Integration Focal Inside Series 8" 4-ohm component subwoofer for select BMW models at Crutchfield
Best Underseat Subwoofer for 2023 - Fast Car
How to install an underseat powered subwoofer.Improve your car stereo`s performance. - YouTube