Bemptil23,
The lows are fine and can extend to what Bob Brines specified as the measured response of the design. Care should be taken to re-inforced the cabinets very well though. As you might noticed, mine have a lot of cross braces. Also, as I might commented earlier, the stuffing and the BSC response is the key. Once you tuned this two to how your room reacts, from my experienced, SS, PP, or SET amps works very well on them. SET sounds better without the BSC in line. But for SS and medium power PP amp (20-60 wpc), the BSC a very good option to have. In my system at least of course and YMMV.
Lcrim,
The link of the picture I posted is my brothers speaker which I have an access to. It was not "beamy" at all. I belive he have at least 90 hours on them. It took him several nights to dial the BSC. But when he finally arrived there, it is worth all the effort. They sound great IMHO.