It's really hard to find a review online in English or someone who has reviewed these speaker in depth.
Searching online will not reveal too much as very few have uploaded their sets.
There is one review on Youtube which doesn't tell anything useful and the reset are nothing related.
I can find a lot of BL5 , BL9, BL18 heck even BL90s reviews online but the BL20s aren't relatively that new.