space makes bass. You arent gonna get any results unless you do a proper enclosure. Which is why the type R and P3 didnt satisfy you, more than likely your box design was cr@p if space is what you care about. Box is what gets you sounding good and loud not the sub brand or model. A 6.5 inch sub in a proper ported will sound louder and better than whatever 12 you have in a crammed pre-made box.
thats the minimum airspace, not the optimum. buuut they can work in much smaller boxes than other woofers. I heard one in .5 cubes and it was completely fine playing down to 25hz. Starts dying off at 35hz though but reaches 25hz.
anywhere from 0.5 to 1 cubic feet will easily work.
It will go pretty deep with that size enclosure. These are mixed use drivers, meaning they work in a home environment so they go DEEP in the frequency response.
