I believe Dave Fokos designed speakers for C-J . I do not know if he designed SL-21.
I own other speaker of his design Icon Acoustics model Parsec. They sound great. Icon Acoustics was his own company. After IA went out of business Fokos worked for Boston Acoustics and Bay Audio. Do a search for Dave or David Fokos.
Quote from inc.com :
In June 1984 (Dave )Fokos, fresh out of college, landed a job as a loudspeaker designer for Conrad-Johnson, a high-end audio-equipment maker in Fairfax, Va. In the next four years Fokos would be the principal designer of 13 speaker models for C-J, an experience he calls "an invaluable apprenticeship" for running his own show. Fokos founded Icon Acoustics in April 1989, believing the niche he sought had scarcely been explored.
I own other speaker of his design Icon Acoustics model Parsec. They sound great. Icon Acoustics was his own company. After IA went out of business Fokos worked for Boston Acoustics and Bay Audio. Do a search for Dave or David Fokos.
Quote from inc.com :
In June 1984 (Dave )Fokos, fresh out of college, landed a job as a loudspeaker designer for Conrad-Johnson, a high-end audio-equipment maker in Fairfax, Va. In the next four years Fokos would be the principal designer of 13 speaker models for C-J, an experience he calls "an invaluable apprenticeship" for running his own show. Fokos founded Icon Acoustics in April 1989, believing the niche he sought had scarcely been explored.