Different strokes........ ;) The early 878B I auditioned didn't impress beyond its relatively deep bass line. The 411 made a fine A7 bass extender though.
Then again, if it and the 846B had been designed with the 802 driver and an optimized XO like the M19 from the beginning, who knows? It's not like Altec didn't have the knowledge to do it as there was no remotely new technology in the M19, so would never have been needed as long as they kept up with the rapidly changing speaker styling occurring back then.
After auditioning the 9848 though, dual horizontally opposed 411s with a 311-90 or large WG were 'dancing' in my head until I got home and back under the 515B's 'spell' that lingers still. :D
GM