SPECIFICATION: MODEL:TRF SPL W1820D1 Size: 18inch Cone: Competition Grade paper Surround material: Foam Voice coil: 3.0inch Voice coil layer: 4layer Nominal impedance:dual 2ohm Voice coil wire:aluminium RMS Power: 2000wrms MAX Watt:4000wmax Sensitivity: 90.2dB Resonance frequency(f0): 29.6Hz Mechanical Q factor(Qms): 6.71 Electrical Q factor(Qes):0.64 Total Q factor:(Qts): 0.59 Xmax: 21mm Force factor: 23.9N/A Magnet Weight: 300Oz Gascet:PVC 1=Outer Dimension:  468mm - 18.42"2=Mounting Depth: 280mm - 11.02"3=Magnet Dimension: 228mm - 8.98"4=Mounting Hole Dimension: 425mm - 16.73"