Order the Reference 15" Subwoofer Kit - SoundImports
Dayton Audio DS270-PR 10" Designer Series Passive Radiator
162*69mm Bass Radiator Rectangular Large Woofer auxiliary Metal Diaphragm High quality 2PCS|Speaker Accessories| - AliExpress
8 Inch Flat Bass Passive Radiator Speaker Resonant Diaphragm Rubber Sheet Iron For 6.5 Inch 8 Inch Subwoofer 215*120mm 2pc - Speaker Accessories - AliExpress
Dayton Audio DS315-PR 12" Designer Series Passive Radiator
51 Gal. DOT Powder Coated Al. Rectangular Transfer Tank