JL Gotham F212 v2 vs ?

m-db,
Thanks for the kind words. I agree with the comments, "There's no right or wrong, "we may exercise more agency, assembling a system that presents the music just the way we like it, and in so doing, participate in the act of creation?" It's about personal preference. As a matter of fact I don't use the high-level connection with my REL subs. I purchased  upgraded speakon cables and compared the high-level connection to the low-level connection. The high-level was connected via SignalCables speakon cables and the low-level via Audioquest Husky RCA subwoofer cables. After a week of listening I preferred the low-level connection...more dynamic and tighter bass. The subwoofers still disappear more than any others subs I've owned. 

The Gotham is a wonderful sub. You might consider instead getting two (or three) of their Fathom f113v2. The reason is that with subs, having several in different locations helps smooth the bass and also gives an increased sense of ambiance.

Two smaller subs also will be easier to move around, if you want to experiment.

JL Audio is a great outfit that makes a great sub. I have two f112 (v1) and they’ve made a huge difference in my systems through the years.

Rythmik F18se or G25HP in duals should be high on your list. with just a little research you'll see why.

http://http//www.rythmikaudio.com/

No matter what speakers I have, I always have a pair of sub to enhance the overall musicality of the system. I can never go back to a speaker system without the support of subwoofers. Prior to my pair of JL F212V1, I was using a pair of Revel Sub30. The JL was a step up in my music enjoyment. Last year, I decided to add 2 more subwoofers to help smooth the bass around the room. Instead of adding JL subs, I bought a pair of Funk Audio 21.0LX. The added Funk Audio subs is another step up in my music enjoyment. I tried to setup the speaker system with the 4 subwoofers but I prefer the speaker system with JUST the Funk Audio subs. Now all 4 subs is used in my HT system. 

@chazzzy007 --

It’s not just about smoothing out modes. Its about recreating the subtle spacial textures in greater detail. [...]

We certainly agree here, but I’d add smoothing out room modes could aid what you point out. Below the Schroeder frequency what needs to be addressed is, to a point, less about preference and more purely about parameters dictated by physics, and it’s why I gave up early chasing the proverbial "holy grail" of bass with the more typical segment of lower sensitivity, direct radiating subs. Apart from focusing on the importance of minimizing room modes with at least a pair of subs, symmetrical placement close to the mains (my hobbyhorse) and, not to forget, overall implementation, there are two aspects in particular that has caught my attention as being essential in attaining great bass reproduction:

One is the SPL capacity at hand and how its abundance (i.e.: LOADS of it) can lead to sufficient headroom, which has the sonic effect outlined in my earlier post. Many seem to believe this approach is mainly about challenging the structural integrity of one’s house/apartment, and that subs capable of this mayn’t be the last word in refinement and subtlety in their reproduction of the lowest frequencies at more sane levels. Given a well executed design, nothing could be further from the truth; the ease of reproduction that follows from huge headroom and low distortion results in a wholly relaxed and pure bass presentation, not least via horn iterations, that brings out the best in the perceived experience of this frequency spectrum. Indeed I’d wager that if more people actually had the opportunity to witness bass like that, fewer would argue against countering subjectivity as a prevailing point of view here.

Following the necessity of or even logic behind above mentioned, another important aspect to my ears is the horn loading of bass, and I’ve already explained why in above post. The rub of it all - achieving headroom, potential horn-loading and upping the number of subs to at least a pair - is BIG size and the need for a minimum of available space, not to mention usually implementing a DIY-approach, and few are willing to or capable of meeting these demands.