[SteveCallas]

You need a loose suspension in order to achieve the ideal FR rolloff that mates well with a <15hz tune. A tight suspension, even in an infinitely large enclosure, will result in a very peaky range around tuning. Also, since a LLT or IB offers little no no resistance to cone movement, the magnet strength becomes less important. High Bl is much more important in small sealed subs, as that magnet strength is needed to compress the air inside the enclosure.