> Many have tried all have failed. Not even Neumann was able to recreate the mic...
Excuse me, but that's just hype. At no time has Neumann ever tried to recreate the KM 84 as such. But tens of thousands of KM 84s were manufactured, and there is a continual need to supply replacement parts for them and for several other older models which used the same capsule. And Neumann still, to this day, makes replacement capsules for the KM 84 that sound exactly as they should. If anything they're more consistent than in the old days. And that's the essential piece; if Neumann did ever decide to re-issue the KM 84 for some reason, the rest wouldn't be nearly as difficult.
The main reason the current mikes don't quite sound the same is that during the 1980s Neumann developed a new modular series of small-diaphragm microphones with transformerless electronics. Meanwhile the "semi-professional" and home studio market had grown considerably, and Neumann decided to cater to that market by giving the new model KM 140 a slightly (ca. 1 dB) greater boost at high frequencies via a redesigned, narrower opening to the back of the capsule. The capsule itself, however, remained unchanged internally.
This process of market-driven change has been standard operating procedure for Neumann for a long time. When the transistorized U 87 was introduced in 1967 as a replacement for the (tube) model U 67, its built-in compensation network was tweaked so that the newer model had slightly more high end. That was in keeping with the times. Now, decades later, they can offer a "retro" model TLM 67 that duplicates the frequency response of the old U 67 to a "T".
It isn't magic or rocket science, in other words; it's straightforward engineering, applied in the service of the company's perceived self-interest. You may not agree with their choices, but that's very different from saying that "they can't build them like they used to." The latter can sometimes be true (many people whose opinions I respect believe, for example, that AKG simply doesn't know any more how to recreate their original 1" capsule, the CK 12), but it certainly isn't true in the case of the KM 84.
--best regards