The prometheus go down to 100Hz and fall off rapidly below that because of the open baffle. Then the dual powered subs take over and provide flat bass down to 30Hz or so. Not too bad considering both speakers, the subs and the sub amp, and the wood kit costs under $2k.
http://www.bastanis.com/diy/prometheus_en.htm
Gary
http://www.bastanis.com/diy/prometheus_en.htm
Gary