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The Braun Cosmophon BMF 2020, from 1933-34, is a quality product from a distant past; a high-performance carbon microphone made in Germany.
The design seems indebted to the Bauhaus school of design, where form followed function.
Here we see a 'machine for the recording of speech and music', wherein all the non-essential elements have been omitted.
For me as a design lover the design has a touching elegance; beautiful in its simplicity and totally different from other microphones of the time, which often had all sorts of finery.

The element was equipped with non sticking carbonates (carbon granules), unlike other carbon microphones which had to be constantly shaken vigorously before use, to loosen the grains for a good signal.
This Braun was almost noise-free and had a constant signal strength that did not vary like other brands of the time, as the carbon granules started to stick together.
The bakelite pedestal houses a transformer output, a 4.5 volt (torch) batteriy and an on and off switch with a control light, the height of the stand is adjustable.
The microphone was fit for work; as command or dictation microphone, but also for home use, for the recording of records or at an amateur radio station.

A portable version also existed: the Cosmophon BMF 2025, mounted in a case. When the lid was opened the microphone automatically came into force.

It is unknown how many of these microphones have been made, but the BMF 2020 with his bakelite foot is very fragile so very little copies of this model have survived until today.

On the internet there is no information available about it, but apparently there was also a version made with a triangular frame for the suspension of the element, as shown in the pictureon the right. The element is evident from the same maker.

Many types of microphones feature in my book Witnesses of Words, which was recently released. More information about that can be found at

wow cover

Braun BMF 2020
Braun Cosmo triangle
Braun Cosmo ad
Braun catalog