In 1932 Marconi-Reisz carbon mics were still in regular use but their days were already numbered.
The other day I purchased a copy of the BBC Year Book 1933 from my usual supplier (ebay). The book covers the period from October 1931 to October 1932. Inside I found an absolutely fascinating chapter on the latest developments in microphones and associated technology heralding the move away from the old carbon mics and the arrival of experimental condensers and the brand new Western Electric dynamic mic. It also describes an innovative new development in the form of equalisation circuitry for correcting anomalies in the frequency response of microphones. The birth of EQ as we know it today. Exciting times!
Here below I have scanned the whole chapter.
Here is some more info about the slack diaphragm condenser
With the arrival of the iconic BBC-Marconi Type ‘A’ ribbon microphone in 1934 the somewhat unreliable condensers featured above were gradually phased out.
P.S.
The 1933 Year Book also celebrates the opening of the BBC’s fabulous new art deco London headquarters in 1932.
Martin Mitchell's Microphones 
Nice post! Now there is a microphone design that didn’t stand the test of time!
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Thanks Stewart. Makes you wonder what other exotic designs fell by the wayside? I had never even heard of the slack diaphragm condenser! The stretched diaphragm model was a Western Electric design made by STC. Both models were completely unreliable and later abandoned. Here is an interesting link to the STC model. https://blog.scienceandmediamuseum.org.uk/bbc-collection-stc-condenser-bomb-microphone/
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