Lowther-Voigt Driver Unit PM1

Lowther-Voigt  PM1

The PM1 was Lowther's first commercially produced permanent magnet drive unit. It incorporates Voigt's light coil, twin diaphragm.

The drive unit was fitted to Lowther cabinets and could also be retrofitted to the Voigt Domestic Corner units replacing the Voigt electromagnet-powered drivers.

Post WW2 Lowther’s chief technician Donald Chave and Voigt Patents, Paul Voight both shared the opinion that the excited-field speaker would be obsolete, and a permanent magnet type was required.
Each worked on the design independently and the outcome was the Lowther PM series, British patents 618,802 & 628,432 registered by Chave.

The diaphragms used in this Lowther PM speaker were supplied by Voigt therefore the speakers were advertised as Lowther-Voigt design.

The magnets may have been produced by Mullard, see article below.

From an article in Wireless Word June 1947, Page 2002.

Two interesting examples of loudspeaker permanent magnet design were seen.
Mullard was showing a " Ticonal " magnet produced for the Lowther Manufacturing Co. having an average flux density of 22,000 lines/ cm², and a double loudspeaker unit for cinema use with centre-pole " Alcomax " magnets was among the examples exhibited by the Permanent Magnet Association. This magnet energizes a tweeter, the throat of which is formed in white metal through the centre core of both magnets. The low-frequency cone has a gap 3” in diameter, 0.08” wide, and 0.5” deep.
Average fluxes are 17,000 lines /cm² in the tweeter and 10,000 lines/ cm² in the large-diameter unit.

Vous pourrez trouver sous ce lien 56 modèles d'appareils, 51 avec des images et 2 avec des schémas.
Tous les appareils de Lowther Manufacturing Co; Kent