B&W claims 4th order crossovers even in their mid-level 600 series speakers. (It's in their 600 Series 2 sales brochure.) Believe I read in another manufacturers sales brochure that use of 4th order Linkwitz-Riley crossovers insured phase and time coherence. That was news to me having "grown up" with the idea that only 1st order was phase/time coherent. I don't know enough to comment on 4th order....just an observation that this seems to be out there as truth.
