That is a good question. Looking into it, B&O does employ class AB amps for mids and highs in their Beolab 7. While their flagship speaker, the Beolab 5, uses all 1CE amps. It's quite a mystery. I sent them a query.
http://www.bang-olufsen.com/UserFiles/File/Products/Technical%20Specifications/BeoLab5_en_na.pdf
http://www.bang-olufsen.com/UserFiles/File/Products/Technical%20Specifications/BeoLab5_en_na.pdf