20W 4ohm Sound Exciter Model: SL-E02 Dimension: outer Diameter 44mmBaffle Opening 14.5mm Height Refer to Drawing in details Nominal Impedance :8ohm +-15% at 1000HZ Power Rating: 20watt Maximum 30Watt Lowest Resonant Frequency :500+-20% HZ Output sound pressure Level(S.P.L): 86+-3db/0.1 Watt.10CMeter.Average at 800,1000,1200,1500HZ Frequency Rang:FO-20 KHZ, Average SPL+-10bd Distortion :5% Maximum at 1000HZ 20W Polarity: Diaphragm shall move forward when Apply a Positive DC current the or Marked Terminal Load Test :Bt audio Signal Generator At 12.6 Volts. Total 48 hours and 20-20KHZ resonant Frequency Abnormal Sound Test: Must be Normally tasted Bt 12.6 Volts Sinwave Operation Temperature:-20deg to 50deg Storage Temperature :-49deg to 60deg.