I reached out to Clair directly. Got my fingers crossed that they will respond.
As I understand the C4 was like a bigger version of the S4. I have only one picture and it is labeled as a Clair Brothers C4. If I can figure out how to post it I will give it a try.
Joseph,
The S4 was all front loaded, originally 440 pounds, "lightened up" in the mid 1980s by replacing the back panel with a foam core composite, dropping the weight to around 400 pounds. Dimensions were 45x 45 x 22.5 inches, standard truck pack integers.
As I recall, the C4 was developed sometime in the late 1980's. I got to see it visiting the Steve Miller tour rehearsals at the Met Sports arena in Bloomington, Minnesota. Steve Wiese, then Steve Miller's sound engineer (and recording engineer for Born 2B Blue) had chose to use it over the S4, as it had better pattern control.
The C4 had horn loaded low mid cone drivers, requiring the cabinet to be deeper, taller and far heavier than the S4. My recollection of the dimensions would be around 67.5 x 45 x 30, weight in the 600 pound range. The large size and weight made it unpopular for most applications, there probably was only one arena system made, and it didn't go out much.
The C4 introduction was not long before the shift to line arrays started, so had a relatively short history.
Art