I would ask him "Why do you think that, Brian?"
You think i should still be considering the rythmic F12? I don't know what kind of clean output it has at 20hz. You hardly see reviews for it.
x-max = 17.8mm
sd = 530cm
= 0.94 L of volume displacement
Assuming the amp is adequately powered, at 20hz, that's about 100db @ 1m (barely perceptable, and 15db lower than reference levels, although it's possible your room does you a big favour)... remember though that this would be with the little 12" driver working as hard as it possibly can, and there might be a powerful, unexpected 15hz tone that comes out of nowhere to push it even harder
Four would do about 12db more I believe, although slightly less if you optimally space them correctly rather than colocate them, but probably significantly more in your small room. Now all of a sudden that 100db at 20hz sounds less like.. well... sound because it's 20hz and isn't supposed to have a sound.
Then you'll probably never need more bass, or better sounding bass, in that particular room, and possibly other HT rooms.
Then you can focus on getting main speakers that excel, rather than trying yet again to find bass nirvana with a flawed approach.
I don't think i have the space for multiple subs.
Then make space... you'll thank yourself later and never be on an endless "chase to find a sub that sounds good unequivocally".
The only spot i could maby put a second sub is in the back left corner of the room, which has a doorway, and behind my LP. Which the sub would have to be up against the wall. Isnt there certain positions you have to locate multiple subs?
No, there isn't! That's what's great about multiple subs, you set them up well and they "dissapear" and integrate to give best response. Obviously having subs in all four corners will maximize excitation of modes and give you the most output, but basically if you can find a place to put it, put it there!
In fact a three or four sub setup will be orders of magnitude less sensitive about placement than a single sub.
Of course you do want similar time delays if they're different distances apart from the primary seating position, but something like a miniDSP ($150) can do that for you. Is that a big investmentÉ