Lowther, AER, Coral, Reps
High efficiency wideband transducers have been around for quite a long time. The technology of coupling an ultralight diaphragm to an ultra powerful motor dates back more than 60 years when Donald Chave and Paul Voight created what was to become the famous Lowther driver.

Lowther DIY sites:


Lowther pm4.gif (29510 byte)
Implementations:  Rethm




Francis Reps took over these basic principles in his own drivers. The R-1 is powered by an 8 pound Alcomax-5 Magnet (aluminum, nickel, cobalt) producing a magnetic field of 20 000 Gauss 

The bobbin is made with a very rigid paper cylinder over which lightweight aluminum wire is wound in such a manner as the thickness never goes over 0,075 mm. This assembly is very light. The bobbin is inserted in a 1 mm gap in the magnet.. The basket is made using high quality Alcoa 356 aluminum. 

REPS R-1 Ultra-2.JPG (7472 byte)
The diaphragm and the whizzer cone are made with very stiff , lightweight German paper. And small ribs are added for extra rigidity. Suspension is
foam material. A brass centerpiece (diffuser) is screwed in the magnet centerpiece. Total cone excursion of the R-1 is 1 mm. Efficiency of the R-1 is 99,8 dB/W/m and distortion at 100 dB is under 0,15 %.

See a finished system using REPS under EXTREME SPEAKERS