inertia

I was wondering how a Fi Q12" sub would perform in a 4.2ft^3 enclosure tuned at 21hz? I would be giving 2 of them each in their own 4.2ft^3 enclosures 1000 watts each from a crown XLS2500 amplifier. Would this perform well or are their better sub options? They would have a subsonic filter at 21hz and then a LP at 80hz. My surround speakers can easily keep up with almost any sub combination out there considering I spent about $4,000 on DIY towers and DIY center channel alone... I hope this being a car audio forum it doesnt bother you guys me asking about home audio... I know a lot of guys using car subs for home theatre.