A THX Certified Select in-wall speaker for 2.1, 5.1 and 7.1 surround systems, using KEF's Uni-Q driver array.Uni-Q driver array as a single point sourceTHX Certified SelectUltra Thin BezelKEF Ci4100QL-THX In-Wall SpeakerSKU: SP3831ASpecifications Frequency response (±6dB): 55Hz-28kHz Sensitivity: 89 dB Nominal impedance: 4 ohms Drivers: 3 x 100mm woofers, 100mm mid, 19mm tweeter Recommended amplifier power: 10-150 W Dimensions (H x W x D): 490 x 128 x 81 mm Cut-out: 476 x 114 mm Weight: 3 kg