Dr. Harry F. Olson began working for RCA Laboratories, where he developed ribbon microphones, first with field coils and then with permanent magnets, resulting in the first ribbon microphones with bi-directional pickup pattern, the RCA Photophone PB-17 and PB-31, introduced in 1931.
[2] A smaller and lower-priced version of the uni-directional Type 77-A, the 44-A's smooth sound and defined pattern control reduced the effect of reverberation on soundstages and offered higher gain-before-feedback in live sound applications, making it a staple of the audio recording and broadcasting industries.
The 44-BX has the ribbon mounted further towards the back giving it a smaller figure 8 pickup pattern on the rear side.
Jon R. Sank joined RCA's acoustical laboratory in 1957, and designed the BK11, a successor to the Type 44.
AEA continues to manufacture recreations of classic RCA designs, as well as new updated variations.