With a movie sub you want one that has genuine bass extension not early roll off.
Some subs start rolling off at 40-50hz and rely on room gain to give a better spec figure but in reality will never have the puff or output in the ulf range to give clean bass.
The reason that is important is because within a certain volume limit subs will sound alike in your room.
They are largely separated by their output capability spl and freq extension and distortion we are not as sensitive to bass distortion.
So if your planning on high spl you need one or more big subs with a lot of clean spl.
If your thinking lower volumes you def want a sub with better extension not early roll off. Bkxls400 rolls off too early really for movies as does that Rel. Svs push for freq extension in their sealed subs as their more movie orientated.
hi mate thanks for that
I've got to ask you a question I looked last night at your home cinema setup on your web page and see your running 2 SVS subs the ultra ones which are a lot bigger the the SVS SB2000 why do you have 2 as the SVS ultras are quite power subs .
your floor standing speakers are just as big as my Dali opticon 8s so it's making me think maybe the SVS SB2000 will not be right for my opticon' s but I want the sub for films only as my opticon' s for music are fine without the need to add a sub .