Gladmo,
you might be hearing a longer group delay that could make it sound “slow” I have not seen the SB2000 group delay but I was a bit surprised at how high the group delay was on the SB 16 Ultra (link below). It was over 20ms. You could argue at that low a frequency it is less important but still about twice what JL does with their subs. The only way to overcome the delay is using an active system to delay the mains. Receivers can do this and same fancy highnesses as well. Well a mini DSP does to but the output stage is junk. anyway just a guess and thinking out loud.
https://www.audioholics.com/subwoofer-reviews/svs-sb16-ultra/measurements