Focal SUB 12 ST6 RED Powered Studio Subwoofer Frequency Response (30Hz – 400Hz) | Reverb
Amazon.com: PYLE-PRO 15 Inch Car Midbass Woofer -800 Watt High Powered Car Audio Sound Component Speaker System w/High-Temperature Kapton Voice Coil, 30Hz-3kHz Frequency,90.2 dB, 8 Ohm, 70 oz Magnet PPA15 , BLACK :
DeltaSonik or PYLE, WP1030/4 10" Woofer PolyPro cone, 4 Ohm 160W, a BOSEy 30Hz | eBay
Vintage 12" in. woofer speaker 3029 30hz - 2khz 50w 6ohm made in Japan | eBay
PLAN] 30Hz 18" EASY TO BUILD LPORT SUB BOX - YouTube