I’ve seen 8″ Elacs used in early WEM combos and also 10″ Elacs used in 4×10″ PA columns

The following pics show a pair of 6×8″ PA columns and a 3×10″ column.

There seems to be very little information about Elac drivers but you can see a little bit about the history of Elac here – Falcon Acoustics / Elac history

(Many thanks to John Beer at Amp-fix for providing this link)