Folded horn *subs*? Good luck finding those. A true horn loaded subwoofer would have a flare frequency at 30 Hz or below, and that would mean a long horn path and large mouth area to boot.The reason what you heard doesn't sound like subs is because they aren't subs. They are gigantic midbass bins, designed for huge output at 50 Hz and above, and little below that.
Probably why you think so many of them suck is because a lot are severely undersized. I've seen 'bass bins' which are supposedly 40 Hz cut, using a pair of 18" JBL's that were small enough to fit in the trunk of a medium-sized sedan. Not happening. A true 30 Hz horn would be the size of a couple of large refridgerators, Let alone a 20 Hz horn.
Adam