These Response woofers are excellent for replacement or for new speaker design constructions. Not only are they price competitive and perform very well, but they also look fantastic! The concave treated paper cone matched with rubber surround provides smooth overall response. Equipped strong steel frame baskets, high power magnet and voice coils, these drivers will produce massive quantities of clean bass output for any musical application. Resonant Frequency 28.1Hz Nominal Impedance 8? Recommended Speaker Box Volume 42l Mounting Hole Diameter (B) 212mm Driver Material Coated Paper Mechanical Q (Qms) 1.46 Speaker Type Woofer Driver Driver Channels Single Driver Total Q (Qts) 0.33 Electrical Q Factor (Qes) 0.43 RMS Power Rating 90W Equivalent Volume (Vas) 42l Frequency Response 38Hz-4.5kHz DC Coil Resistance (Re) 6? Side-to-Side Diameter (A) 220mm Cutout Diameter (C) 182mm Insert Depth (D) 92mm Cutout shape Round Attachment / Securing Method Screw Down Mounting Method Front of Panel Diameter 220mm