That pretty much says it. Offset drivers were thought to be best practice back in the day. The idea was that diffraction peaks and dips to one side of the speaker would be different than to the other side, and would tend to offset each other in the overall room response. I don't think there were ever any blind, controlled tests to see whether the theory actually made any audible improvement. I never heard any between the old BMR's and the new in-line--they sounded the same, perhaps because the drivers were so smooth off axis to begin with. Today, following the research of Floyd Toole and others, the design goal is even off-axis response to either side of the speaker. That's tricky and requires very careful selection of drivers and crossover points, or resorting to a wave guide for the tweeter (which has problems of its own), but at least the designer can tell whether that' objective has been met by performing the proper off-axis measurements. With offset drivers, you never know what you've got off axis, because the response to one side will never be the same as the response to the other side. My current Affordable Accuracy monitor uses a very old-school Parts Express cabinet with offset tweeters, and I went crazy trying to optimize its response. A $100,000 Klippel machine will tell you, but so far I'm about $99,000 short of acquiring one.
