Ok, I'll do my best to describe this as it was back in the day (early 90's). Buddy had a pair of 8's that sounded absolutely incredible!!! People used to always think he had 12's or bigger - LOL! System was a high end Alpine head unit, Infiniti components, Orion Amps, etc.
Best way to describe the box (one for each speaker) was a big rectangle. Maybe around 42" long. Depth and Height was probably around 24". Recognize I'm pulling these numbers straight out of my a$$ so I could be way off on dimensions as 20 years can cloud the memory a tad. You couldn't see the speaker. It was basically mounted in the center of the box. Each end of the box had a slot that ran from side to side and was probably 3/4-1" thick.
I hope I described that correctly. If not let me know what isn't clear and I'll try to explain it better.
Bottom line, you had to have space, but or what they were those speakers POUNDED!!!