Well, I don't know how much my response is worth, but here's what I think:
First, I'll preface my opinion with a question: Aren't the BL9's made in the Czech Republic?
I ask because maybe their quality control isn't quite up to snuff as compared to good 'ol Denmark.
I remember reading a review of the BL5's where an engineer enthusiastically stated that they 'don't build BL5's, they CLONE them'.
Anyway, regardless of where they're built, I'm thinking that maybe the BL9's don't quite get that same level of attention, and possibly the person who put your pair together wired one of the midrange drivers out of phase. That would cause some cancellation around the X-over points, and probably between each other. Only way to know for sure, like Mr. Moulton said, is to measure them.
By the way, I have to agree with everyone else here. The BL1's are the latest speakers I've heard from B&O. I haven't heard the ALT speaks. Anyway, the 1's sounded horrible to me. Shouty mids, harsh sounding (and I believe the mid and tweeter used conventional Class AB 75w amps, not the IcePower stuff), but with nice quality, although weak, bass. Thinnest sounding B&O speaker I've ever heard. When I listened to that speaker, my eyes flinched, and I walked away very, very disappointed. Sure did look cool though....
I firmly believe my MS150's would walk the floor with the BL1's, and even doubly so since I substituted in a 7 ohm resistor in lieu of the 2.2 ohm series resistor on the filler driver (R18 I think, if anyone else wants to try it and see). They sound just perfect now. :)))))))))))))))))))))))))))))
Jon