OK... I did move the speakers; I didn't have alot of room to play with, but now, at a distance of 30" from the wall, rather than 10", the bass is much more defined. In fact, it sounds pretty darned good on well-recorded cds. The sounds-stage is deeper and imaging is better. Could it be better? Probably, but I don't have the luxury of a dedicated listening room. I contacted silverline and Alan Yun asserted the speakers are "desiged to be ported" and that plugging the ports "could damage the woofers". Perhaps this is his standard fine-print disclaimer and does not so much represent an actual risk, but even so, I'm not inclined to start stuffing anything into the 17.5's. For me, they were an expensive purchase. I'm still going to try what others have suggested, in addition to speaker placement.I don't think it has to be a black and white, "this" or "that" approach.