Retro-thermionic not only produces valve amplifiers and preamplifiers but also some finished speakers. Currently retro-thermionic is having constructed the back loaded enclosures to accommodate the Fostex FE206E drivers. After evaluating the the Fostex driver in a simpler two chamber enclosure, retro-thermionic, decided to have the more complex labyrinth style enclosures made. A CNC cutting machine was employed to make the most efficient cuts from the expensive and heavy 21mm multiply timber. Some panels are double layers of 21mm multiply. Panel bracing is extensively carried-out to control box colouration.
Sandbags can be layed in the bottom of the horn to tailor the bass to the listening room. Sandbagging can also be performed in the driver chamber to alter the level of other low frequencies. With efficiencies of the drivers reaching 96db the retro-thermionic amplifiers can produce high sound levels easily.
