Epik 15" DIY Ported Subwoofer | Home Theater Forum and Systems
15 Inch/12 Inch Audio Speakers Passive Radiator Diaphragm Bass Subwoofer Speaker DIY Repair Parts Accessories - AliExpress
One unit (not pair) |15 Inch Woofer for Bass Compensation of Open Baffle or Cabinet | W-15 - Lii Song (Lii Audio), unique speaker, amplfier, quality and cost-saving parts for HiFi DIY
How to Design Your Own DIY Subwoofer - TurboFuture