Sony ECM-50
The microphone small enough to disappear on a lapel - and the one that launched an entire category of electret condensers.
Overview
Sony itself calls the ECM-50 the world's first electret condenser lavalier. The claim is preserved in the company's own ECM-55 series documentation, which describes the later ECM-55 as the "successor to the ECM-50 microphone." That tells you the most useful thing about this mic. Everything that came after in Sony's professional electret lavalier line came after the ECM-50.
The big idea was putting an electret element in a lavalier body. Sony's own advertising in DB-Magazine (October 1970, p.7) pitched the ECM-50 to TV announcers "long burdened by the cumbersome lavalier version of the standard dynamic microphone." It called the mic a miniaturized Tie-Tac/Lapel condenser, "so small it literally cannot be seen." That's marketing copy, not a measured verdict. The design argument is plain enough, though: give up the bulk of a dynamic lav for an electret condenser element small enough to clip to a tie.
The mic shows up in Sony's period advertising next to the ECM-22 (an electret condenser with on/off switch) and the ECM-51 telescopic electret. The company ran these together as a family of "Sony firsts" in DB-Magazine (August 1969, p.9) under the banner "Innovation through imagination." The ECM-50 was positioned for field interviews and broadcast work. The same ad run described it as acting "like an extension of the reporter's arm."
By the early 1980s the ECM-50 was a stock item in professional circles. Studio-Sound (June 1981, p.37) listed it among Sony's professional microphone range "available from stock." The listing noted the line had been "used extensively in studios throughout the world for many years" and was recognized for "quality of manufacture." The same listing, repeated across several 1980-81 issues, grouped the ECM-50 within Sony's four microphone types - FET condenser, dynamic, electret, and back electret.
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