The Sennheiser HSP 4-EW is a high-quality permanently polarized condenser headmic with cardioid pick-up pattern, designed for professional "hands-free" applications. The adjustable neckband is visually unobtrusive and very comfortable to wear.
Pick-up pattern: cardioid
Frequency response: 40...20 000 Hz
Nominal impedance (@ 1 kHz). 1000 Ohm
Min. terminating impedance: 4700 Ohm
Sensitivity in free field, no load (1kHz): 4 mV/Pa
Maximum sound pressure level (passiv): 150 dB
Equivalent noise level: 37 dB(A)
Current consumption: ca. 250 µA
Operating voltage (stand alone): 4,5-15 V
Cable length: 1,6 m
Excellent feedback rejection
Microphone includes a detachable cap as integral wind/popshield
Individually adjustable to all head sizes Neckband design keeps the microphone clear from shirt-collar or clothing
Twist-proof microphone boom (Ø 2.0 mm), can be attached to the left or right side
Microphone boom is adjustable in length and angle
Flexible gooseneck section
Connection cable can easily be interchanged
All metal parts coated in a physical vapour deposition process
Can also be used with the omni-directional HSP 2 boom microphone
Delivery includes: boom microphone, neckband, connection cable, plastic transport case, foam-lined with cut-outs
DPA d:fine™ CORE 6066 Omni Headset Mic, beige, Mini-Jack
Sennheiser HSP 4-EW-3 Condenser Headmic 
Sennheiser Headmic 4 SB
Sennheiser HSP 2-EW-3 Headmic Microphone