I am wracking my brain right now: I just answered the same question somewhere but cannot find where...So here it goes again:
The U47 capsule mount is at the end of a stiff rubber column whose height and material properties need to be an ideal compromise between elasticity (shock absorption) and stiffness (preventing the capsule to whiplash against the inside of the head basket after a shock). Making it shorter gets you into the territory of the C12 and its capsule mount problem: heavy subsonic Trittschall-transmission. The whole thing transmits too much at 20 hz and below when triggered with even the smallest external excitement.
The secondary, and probably unintended (positive) consequence of the column length Neumann chose is this: the higher you place the capsule inside the basket, the father away it gets from two parallel and reflective surfaces-the basket wall and the base plate-and the closer it gets to the domed (and diffractive) top.
Here is an experiment I have made a few times to understand the real-world consequences of an acoustical obstacle placed close to a diaphragm: mount the same CK12 capsule, once in a C12 (no obstacle in front of the front diaphragm) and then in a C24 (a nasty support bar crossing right through the middle of the front diaphragm): I cannot hear an difference.
That leads me to believe that the small circular weld connecting the U47's cylindrical basket with the domed portion of the basket must be quite negligible, acoustically.
