
The fronts have the single driver.
It really does sound better.
I can tell you after an hour of listening that these are not junk, and deserve serious attention and evaluation. My original (series 1) 901s are very well built, with excellent plywood cabinet construction. They pass the knuckle test solidly. All 18 drivers are good, with no deterioration in the original treated cloth surrounds, and are well sealed with putty. Eight 5 inch drivers per side generate a lot of internal air pressure, and the cabinets are up to the stress. There are no crossover caps to deteriorate, because there are no crossovers!
The speakers are not intended to be used without a purpose built equalizer box, which I do not have. I obtained frequency response curves for the series 1 equalizer easily on the internet (including the curve from the BOSE Corporation's patent), and set the curve and saved it as a custom equalization setting in itunes for my initial listening. The curve is extreme, up 12 db at 30 hz, so a powerful amp is a necessity, and the Adcom GFA-1, at 200 watts/channel, fills the bill nicely.
The many different ways that so many talented engineering minds have attacked speaker design (planar, dynamic, full range, transmission line, sealed, ported, infinite baffle and numerous hybrids to name some), are what make this obsession of ours so much fun. Never mind the overpriced crap the the Bose Corporation has produced. This was a ear opening design when it was introduced in 1968, and it still is.