Yamaha 8” Subwoofer, small footprint good bottom end.

NS-SW050 Specifications

Subwoofer Driver: 8" cone
Dynamic Power: 100 W (5 ohms)
Output Power: 50 W (100 Hz, 5 ohms, 10% THD)
Frequency Response: 28–200 Hz
Advanced YST: Yes
Twisted Flare Port: Yes
Dimensions (W x H x D): 11-1/2" x 11-1/2" x 13-3/8"
Weight: 18.7 lbs.