THX Certified Ultra 200mm In-Wall Subwoofers (2)Brand New in Box! Total of 2 Subwoofers. Hundreds off to clear my storage - These are $999.99 at Best Buy right now! Bid and purchase with confidence - I am a 100% positive feedback ebayer for over 15 years!! Any questions be sure to ask! Thank you and goodluck!! THX Certified to the level of Ultra and Select, the formidable Ci200QSb-THX in-wall subwoofer delivers deep bass and theatre thumping output capabilities, matched to the uncanny ability to deliver all the drama and emotional intensity of full theatre sound quality. With a powerful high-output 200mm (8in.) sub-bass driver, the Ci200QSb-THX can be used in passive mode to supplement the LF output of KEF’s in-wall or in-ceiling speakers. In Active mode, when 2 pairs of the Ci200QSb-THX subwoofer are powered by 2 KEF KASA500 System Amplifiers the performance meets THX Certified Select specification. When 4 pairs of the Ci200QSb-THX are powered by 2 KEF KASA500 System Amplifiers the performance meets THX Certified Ultra specification. Nominal Impedance6 Ohm - Passive Mode (Crossover ON)N/A - Active Mode (KASA500)Sensitivity85dB - Passive Mode (Crossover ON)N/A - Active Mode (KASA500)Crossover Frequencies100Hz - Passive Mode (Crossover ON)N/A - Active Mode (KASA500)Frequency Response40Hz-100Hz - Passive Mode (Crossover ON)18Hz-140Hz - Active Mode (KASA500)Drive UnitsLF: 200mm (8 in.)Recommended Amplifier Power10-150W - Passive Mode (Crossover ON)KASA500 - Active Mode (KASA500)Product External Dimension (H X W X D)Diameter: 273 x 273 x 106 mm (10.75 x 10.75 x 4.17 in.)Cut-Out Dimensions (H X W)238 x 238 mm (9.37 x 9.37 in.)Mounting ThicknessCeiling Thickness (Maximum): 40mm (1.58 in.)Ceiling Thickness (Minimum): 6mm (0.24 in.)Mounting Depth From Surface101.6mm (4 in.)Optional Rough In FrameRIF200SNet Weight3.3kg (7.28 lbs)Unit MeasurementPiece