JBL LSR310S 10 inch Powered Studio Subwoofer With XLF - Extend your system LF all the way down! 

Features:

• The LSR310S subwoofer incorporates JBL’s patented Slip Stream Port working in concert with a custom 10” down-firing driver and a 200 Watt amplifier to add deep, powerful bass to any studio monitor system. 
• A JBL first, the XLF Extended Low Frequency setting lets you hear your tracks with the augmented bass tuning used in today’s dance clubs.