Amazon.com: for a 06-12 BMW 3 Series E90 / E92 - Custom Sub Enclosure Subwoofer Box - 2 12" Subs : Electronics
Underseat Woofer for BMW 3-Series [F30 & E90]
Car Subwoofer For Bmw F10 F30 G30 E90 Series High Quality Under Seat Low Range Frequency Loudspeaker Bass Speaker Horn Stereo - Multi-tone & Claxon Horns - AliExpress
BMW 3 Series Sub Box BMW 3 Series Subwoofer Box E90 Sub Box E92
Base Stereo Subwoofer Upgrade Guide - BMW 3-Series (E90 E92) Forum
HOW TO REPLACE UNDER SEAT SPEAKER SUBWOOFER BMW E90 E91 E92 E93 - YouTube