Audiopipe TSCVR6 TSCVR Series 6-1/2 inch Subwoofer - Dual 4 ohm voice coils
Amazon.com: Lanzar 6.5” Car Subwoofer Speaker - Black Non-Pressed Paper Cone, Aluminum Voice Coil, 4 Ohm Impedance, 600 Watt Power and Foam Edge Suspension for Vehicle Audio Stereo Sound System - MAXP64 : Electronics
Audio Dynamics 6.5 Subwoofer | Speaker Subwoofer 6.5 Inch | Best 6.5 Inch Subwoofer - Speakers - Aliexpress