They are (or should I say were) great speakers but I do not think you will be able to get drivers for them, unless you get lucky on ebay. Reference 3A has had a complicated past. The speakers were designed by Daniel Duhay or Dehay or something like that and were made in France and/or Switzerland in the 80s/90s before the brand was sold/moved to Canada. You might also find some information under Innovac from Switzerland. The magazine/-zine UHF from Canada has information. The Master Control monitor was also sold in combination with an iso-baric loaded passive subwoofer as an early two piece bass cabinet/monitor top speaker.