Model Sound quality midrange speaker Diameter 55 mm / 2.17″ Power Handling (RMS/max.) 90 / 150 Watt Impedance 4 Ohms Efficiency 88 dB Frequency Response 500 Hz – 11 kHz Voice Coil 55 mm / 2.17″ Membran Layout Coated silk Magnet material Neodymium Mounting Depth 33 mm / 1.3″ Mounting Ø 69 mm / 2.72″ Resonance Frequency (Fs) 353 Hz.