The Sennheiser HMD 25-1 headset with microphone is designed on the same pattern as the HD-25, but its acoustic characteristics are inferior, with 600 ohm impedance for each phone. It can provide sound pressure level of 102 dB, with total harmonic distortion lower than 1%. Its response curve is reduced for high frequencies and goes from 20 Hz to 16 kHz
The supercardioid mike is perfectly suitable for an intercom system, with 1 mV/Pa sensitivity and reduced response curve from 100 Hz to 16 kHz.
So the proper use of this headset is more in an intercom system than for genuine sound recording.
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