<主要スペック> https://www.kenrockwell.com/audio/stax/new-sr-3.htm Impedance: around 130 k Ohms at 10,000 Hz. Capacitance: around 120 pF. Sensitivity: around 95-100 dB at 100 V RMS. Frequency Range: 30 - 25,000 Hz, but I had no problems getting 20 Hz out of it.