SB ACOUSTICS SB21SDCN-C000-4, 20mm TEXTILE DOME NEODYMIUM TWEETERFeatures Large surround dome for increased acoustic output Copper cap for reduced voice coil inductance and minimum phase shift Compact low distortion neodymium motor system Non-resonant rear chamber with optimized damping for improved dynamics CCAW voice coil for low moving mass Long life silver lead wires Low resonance frequency Specs Nominal Impedance 4 Ω DC resistance, Re 3.1 Ω Voice coil inductance, Le 0.04 mH Effective piston area, Sd 4.9 cm2 Voice coil diameter 20.4 mm Voice coil height 1.5 mm Air gap height 2.0 mm Linear coil travel (p-p) 0.5 mm Moving mass incl. air, Mms 0.25 g Free air resonance, Fs 850 Hz Sensitivity (2.83V/1m) 90 dB Mechanical Q-factor, Qms 2.44 Electrical Q-factor, Qes 2.45 Total Q-factor, Qts 1.22 Force factor, Bl 1.3 Tm Rated power handling* 40 W Magnetic flux density 0.9 T Magnet weight 0.01 kg Net weight 0.06 kg * IEC 268-5, high-pass Butterworth, 2600 Hz, 12 dB/oct.