Amazon.com: PyleUsa Car Midbass Speaker System - Pro 8" 600W 4 Ohm Mid-Bass Component Woofer Audio Sound Speakers for Car Stereo w/ 40oz Magnet,Tweeters, Grills, 45Hz-4KHz Frequency, 3.1” Mount Depth-PLG8C (Pair) :
Amazon.com: PRV AUDIO 6.5 Inch Speakers Midbass Woofer 6MB200-4 v2 200 Watts Program Power, 4 Ohm, 100 Watts RMS, 1.5 in Voice Coil, Perfect for Small Custom Enclosures for Pro Car Audio
Eminence Beta-6A 6-1/2" High Power Midbass Midrange Woofer Speaker
Tech Talk: Mid-bass Madness - Getting the most out of your door speakers - DD Audio