I just bought a used Sony ECM-672 Microphone, unfortunately the owner wasn't the original owner and doesn't know what the low cut filter settings mean? If anyone could explain to me the difference between the M and V setting, I would appreciate it!!

Thanks!

Daremo:
Haven't used an ECM 672 in some time, but if memory serves me right, the M = Music setting and the V = Voice setting.
At the M/Music setting, the low cut filter is bypassed (i.e. you get a flat frequency response with no adjustments in mic). At the V/Voicesetting, the mic inserts a low cut (approx. 80 - 400 Hz. range).
Use the V setting with care: I used to prefer recording on the M setting all the time, and do my sound adjustements in post...the V setting can make your audio sound pretty shrill in ways you wouldn't expect. It's best used in extremely controllable situations, like a quiet room interview setup, where it affects only what you want it to affect - the voice of the eprosn being interviewed. [But I used to record those on the M setting as well! :-) ]
The V setting works when you're trying to cut traffic rumble in an outdoor doc setup - but don't try to cut wind rumble with it! Use a wolly and a Rycote type windshield!
Hope this helps!
Ram

Daremo:
...just to add a small point. The cut peak for the V setting on the mic is somewhere near 200 MHz (i.e. almost exactly midway in the range I've specified.)
Best,
Ram

Thank you!! I appreciate the information, it really helps!