When the original Telefunken GmbH company lost its contract for OEM U 47 microphones built by Neumann, they tapped into AKG in Vienna for a slightly redesigned version of the popular C 12 microphone. With the same tube, transformer, and capsule, the Telefunken ELA M 251E built by AKG is nearly identical to the C 12, with a few key differences. Rather than having remote pattern switching, the ELA M 251E has three selectable polar patterns (cardioid, omnidirectional, and figure-of-eight) as part of the microphone's head assembly. The physical orientation of the tube in the 251 is flipped 180 degrees, with less wire between the capsule and the tube. Cathode bias, grid coupling, and capsule polarization are also different. Most notably, the head baskets of the two microphones are significantly different from one another leading to different acoustics surrounding the capsule.

The ELA M 251 is nearly identical to the ELA M 251E -- the E designation is for "Export" which meant that the microphone was to be sold to the United States, and was equipped with a 6072 tube. The non-E version used the AC 701k tube, which broadcast studios could easily power with their existing N52 "cassette" module power supplies.

Being one of the most iconic, widely-used vocal recording microphones, original examples of ELA M 251E microphones are among the most desirable microphones ever produced, with prices well into the five-figure range.