I recently bought a secondhand neumann KMR 81i. I'm totally new to sound recording and microphones. I want to use the microphone for film and video productions. At the same time I bought an Audio Technica AT875R to put on my video camera. While trying bought microphones out several times, I noticed that the KMR 81i's output is 10db lower than the Audio Technica AT875R. I was a bit surprised about this because the KMR 81i is defined as a highly sensitive microphone. When I want to record a sound , for example of running water in the sink or even a voice I have to turn up the gain a lot, so I get a lot of noise. It's very difficult for me to interpret the specifications of both microphones, so I will give you some (hopefully usable) info here (KMR 81i: 18 mv / Pa +1 dB / AT875R: 31.6 Mv). Could it be that my old KMR 81i has not the same output level as the new KMR 81i because the specifications changed in time? I hope someone can give me an answer why the KMR 81i's output level is 10db lower than the Audio Technica. I will also give you the serial number of the microphone: 10302. Could someone from neumann maybe tell me the year of production of the microphone?