How do I know if I need a sub woofer?

@gournard Somebody here said their sub is too slow! No such thing as a slow, boomy or one-note-bass sub. 

Before you criticize, make sure you know what you’re talking about. The “slowness” of a subwoofer does not refer to when the bass notes start (attack), but rather to when they stop. In fast passages, the bass note fails to stop in time before the next one begins — that’s the common understanding of subwoofer pace. Changing the phase, even discretely, does not affect or control when a note stops. I always prefer and use sealed-enclosure subs, but that alone doesn’t help much. I also use bass traps to reduce ringing from standing waves; this helps, but only slightly. Ultimately, control must come from the source.

I also tap the signal directly from the main-speaker terminals to take advantage of the main amp’s high damping factor. Again, this helps, but there’s still much left to be desired. The only thing I still hope to try before concluding this journey is a servo-controlled subwoofer.

So again, make sure you understand why there is no such thing as a truly ‘slow’ subwoofer. Do you really know what a slow sub sounds like? My colleague once complained that a large 12" sub was slow and swapped it for an 8" sub to address the issue. But until then, why would I even need a sub? If you feel you need a sub as a panacea to achieve a good soundstage, then either something is wrong with your main system, or you are not optimizing it properly.

Bass reminds me of my drinking days: "I had three beers and felt good, why did I think that three more would make me feel better" 

Oh dear. To address your apparent complete misunderstanding would take too long so I won't bother. You do you.

I provided you with the names of some extremely well informed people to read up. If somebody writes their thesis on this subject then I think it's fair to assume they know what they are talking about. 

Have you read anything from those authors? No I didn't think so.

I will not respond to anymore of posts.

sounds_real_audio OP, I hope you did not suffer too much with all the above. I attempted to explain that all rooms regardless of the speakers' size will benefit greatly from a pair of subs however it seems to have ruffled some feathers.

Good luck in your quest.

Two Blue Jeans 45' Canare L-4E6S shielded star quad XLR stereo pairs to Velodyne DD Plus through put to a second DD Plus. Approximately $230.