"Sennheiser HMDC 27 Professional Broadcast Headset - over-ear desin, closed back, NoiseGard (active noise reduction) reducing the noise level by additional 15dB, no batteries needed, it is conveniently powered via the..."
"Sennheiser HMD26-II-600-S Professional Broadcast Headset - dynamic, closed back and on-ear headphone, impedance 600 ohms momo, sensitivity 107 dB SPL/1 kHz, 1V, frequency range 20 - 18000 Hz, microphone: typ BMD 424,..."