The cheap set just had one driver each, and looked shot. I couldn't find a convenient opening(glue sealed box, bottom-mount driver)so I just hammered about an inch from the driver. I hit it pretty hard, but no hole. The weird thing is the cone jumped out, like I had played it really hard and it blew. I pushed it back in and repeated the process a couple times until I slipped and hit the cone.

I imagine the hammer strike made an increase in pressure (cheap box), causing the cone to pop out.

This makes me think again about shared enclosure space for subs, as it seems it would cause distortion. I also see why if you have your subs like that and one stops playing it might get killed.