Source Sennuopu Car Active 500W Spare Tire Active Bass Subwoofer 10 inch Auto Audio Subwoofer Speaker on m.alibaba.com
Bose Spare Tire Subwoofer in Toyota Avalon - YouTube
Spare tire subwoofer with built in amp in Civic ExL hatchback | 2016+ Honda Civic Forum (10th Gen) - Type R Forum, Si Forum - CivicX.com
For those of you who want more bass but don't want to sacrifice your spare tire or hatch space, I highly recommend this spare tire mount subwoofer : r/GolfGTI