Agreed, they could be more efficient. I'm not sure how practical it would be to increase Bl or magnetic flux density much more than they already are, I've seen the drivers and they don't skimp on magnets. I think it's just a tradeoff in terms of achieving that "pistonic" performance, which requires a very rigid cone. While they take pride in machining everything out of aluminum in-house it's possible they may achieve a lighter cone that is just as rigid out of other materials, this + increasing cone surface area would be one way of making further improvements in terms of efficiency and I think it would help with overall bass quality and dynamics as well. If I could fault them for one thing it would be lack of woofer surface area, but then you can just buy Sonja XV I guess...