Marconi-Reisz 'Marble' Microphone

Made:
1927-30 in Chelmsford

Marconi-Reisz marble encased carbon microphone, 1927-30. Based on a German design by Reisz, it was a transverse current carbon type of microphone. It was constructed in a hollowed-out marble block, fine carbon dust was held between output electrodes and fronted by a mica diaphragm.

Sensitivity was good and noise performance acceptable, but there was a pronounced resonance at 5kHz, subsequently cured by substitution of a rice-paper diaphragm. There was a marked non-linear distortion (blasting) at high sound levels which necessitated careful placing of the microphone relative to the artists. Despite some shortcomings, this microphone gave good overall performance and was much smaller and more portable than the Marconi-Sykes Magnetophones introduced in 1923. By 1927 the Marconi Reisz was in virtually universal use, continuing well into the 1930s. This carbon microphone needed to be turned over daily to prevent the granules inside from settling. Although not nearly so sensitive as the earlier Round-Sykes microphone, it was far more widely used by the BBC because it did not require the same very high level of amplification

Details

Category:
Television
Collection:
BBC Heritage Collection
Object Number:
2012-5118/860
Materials:
metal (unknown), brass (copper, zinc alloy), steel (metal), wood (unidentified) and textile
Measurements:
overall: 105 mm x 130 mm x 85 mm, 1.76 kg
type:
microphone