I remember someone asking about these systems a couple of years ago; it
seems that some erroneous information about them was tossed about, but, although I don't have technical data, I do have some first hand experience with them. I ordered a pair "drop-shipped" while in the Army in Germany in 1971, and they were delivered to my apartment in Morgantown when I returned to school in early 1972. The Altec Lansing factory representative who had demonstrated them in Frankfurt said they were designed for monitoring in small studios and that they were the first commercially available systems to be based on the Theile Small parameters. They were a shade over twelve inches wide and almost exactly two feet high, but less than a foot deep. They featured a ten-inch woofer and a ten-inch passive radiator, the first systems I ever saw with such a device, and a two-inch tweeter located midway up the baffle, nestled as close as possible between the two large speakers near the outer edge. Everyone who ever heard them was impressed with their high efficiency, articulated sound, and general "tight" imaging. The bottom end was not so extended as that of the Larger Advents, but the rest of the spectrum was more clear--bright, but not harsh. I was an idiot for ever selling them. I have searched in vain for any technical information concerning them, but have, very occasionally, seen a pair for sale.