Produced from 1932 - 1955, the RCA 44-BX is perhaps the single most recognizable ribbon microphone and something of an icon in the world of broadcast and recording history.

The 44-BX is a high-fidelity bi-directional ribbon microphone designed for music recording and broadcast. It uses a 2" long corrugated aluminum ribbon which is just 1.8 microns thick, roughly 1/20th the thickness of a human hair.

The frequency response from a 3 foot distance is quite flat from 50Hz - 15kHz, followed by a steep high frequency rolloff. The bass boost from proximity effect becomes quite apparent at closer distances, and so jumpers are provided inside the microphone to allow for two high-pass filter positions (V1, V2 -- "V" for "Voice" which is typically picked up from closer distances).

The only major difference between models 44-BX and 44-B is how the output cable comes out of the microphone's housing. Some examples of 44-BX have the ribbon assembly placed further back in the head basket, but this is thought to be due to inconsistencies in manufacturing and not necessarily a change in design.