4 Inch 40W-100W Subwoofer Speaker 4Ω 8Ω High Power Long-Stroke 2Way Divider Bass | eBay
Test Bench: The SW26DBAC76-4 Shallow-Mounting Subwoofer from SB Acoustics | audioXpress
Amazon.com: hejhncii 4 Inch Subwoofer Bass Speaker Carbon Fiber Cone Woofer, 4/8 Ohm 40W Low Frequency Car Audio Speaker : Electronics
BOSS Audio Systems CXX8 Chaos Exxtreme Series 8 Inch Car Audio Subwoofer - 600 Watts Max, Single 4 Ohm Voice Coil, Sold Individually, For Truck, Boxes and Enclosures, Use With Amplifier
Amazon.com: CHOOYO 5.25 Inch Subwoofer Speaker 4 8 Ohm 60W Woofer Audio Modification Deep Bass Bookshelf Loudspeaker for Home Theater DIY 1P (Color : 8 Ohm, Size : 5.25") : Electronics