These speakers are really unlike any others. Bob Fulton was a real genius with sound. I have the Jmod setup with the large bass module. The base module I have is 26" wide x 22" deep and stands 33" high. It has the front firing 10" and the down firing 12". Bass this thing can put out is earth shaking. If not for their size and weight(there only negative), I would say these are the best speakers I have ever had. They certainly are the best I have ever heard.
I bought my set from the original owner who had purchased them while living in California. He knew Bob Fulton and these were actually tweaked by Bob himself at his home. I asked what tweaks Bob made and he said when Bob talked it was so over his head he really couldn't tell me. Bob loved to tweak these as you can see by pictures of his elaborate crossovers. The owner of the speakers I now have told me Bob was never satisfied with the sound any of his speakers produced, he always thought he could do better. His goal was to make a speaker which would ultimately sound exactly like the instruments and singers on the recordings and not like a speaker.
I will tell you that since I have had mine I have determined that the bass mod loves power. I think you need a fast powerful amp to control those woofers.
Congrats on finding a real piece of musical history. I know I will never let mine go! Here is some info I found.
Description: Four-way, five–drive-unit, floor-standing loudspeaker (J-Modular, including two Model 80s). Nominal impedance: 8 ohms. Power capacity: 60W program.
Dimensions: 17.5" H x 9.75" W x 8.5" D (Model 80); 33" high x 18" W by 18" D (Model J woofer).
Price: $188/pair (Model 80, 1973), $1196/pair (Model J-Modular, 1975–1977); no longer available (2006).
Manufacturer: Fulton Musical Industries, 4428 Zane Avenue North, Minneapolis, MN 55422 (1973–1977). Company no longer in existence (2006).