A bit more about that "Broadcast Filter" in M49s:
*There was none in the first edition (w/ Hiller MSC2 tube, later often replaced by Neumann during service with AC701.)
*There was a barley perceptible (and, according to the specs, non-intrusive) high frequency attenuation on M49 mics built from ca. 1952 to ca. 1961- 150pf shunt to ground.
*In 1961 and for the remaining years the mic was made, the shunt increased to 600pf, but, again, according to the specs, frequency response of the amp remained flat, from 10k to 15k.
If you are so inclined, simply remove the shunt, and your psychological perception of regaining lost high end will be satisfied.