Why so many JL Audio Fathom subs for sale I wonder

Well you know what? You've all convinced me that buying a JL Audio sub , maybe 2, is going to be ok. This is great to hear, and everybody who's contributed to this thread has made alot of sense, so thank you all for your input. I think I'll just snap me up a Fathom F113 and give it a spin in my listening room. Or would anyone suggest I buy an Fathom F212?? My listening room is approx. 15 feet wide x 18 feet deep with 9 foot ceilings. I'm running MBL 101e Mk2's with MBL 9008A's and a MBL 6010D. Already a pretty potent match, and when I run my JM Lab / Focal sub...the result is quite good. Actually it's DAMN good (not to sound like a braggart or anything). If I step up to a single Fathom F113 do any of you think that would be "sufficient" given my room dimensions? I wouldn't be looking to use the JM Lab /Focal sub in the mix any longer. Just a single (maybe a pair?) of F113's. Or just a single F212. Again, as mentioned in my original posting, I'm a bass freak. So it absolutely MUST play clean, tight, loud as hell, and hit like a sledgehammer. The JM Lab / Focal I have IS all that...but only to a point. I'm looking for "bone-crushing" bass. (Yeah, I'll admit it. I'm into ROCK, and Heavy Metal, hence MBL speakers, amps, and Preamp.) That having been said- and given my room dimensions- what would YOU folks do with regard to my quest for monster, ass-kicking bass?? 1? a pair? Like to see where others would go with this. Thanks in advance for humoring me about this.

I went for two F113's over one F212. My room is about 18x30 10' ceilings.

04-27-13: Jp1208
I went for two F113's over one F212. My room is about 18x30 10' ceilings.
Jp1208 (Answers | This Thread)

Hello Jp1208, thanks for the input. Question for you: did you hook them up as independent subs, each with their own signal input from the preamp/processor? Or did you link them together using the "master/slave" configuration.

And whatever you did, would you mind giving me more input about what you thought? or the percieved differences?

I had them as independent at one point when running Ming Da pre and two Linn Klouts. Things changed and now they are running together through a modified Onkyo reciever. Running the ARO as separate or in master didn't seem to make that much difference in my room so I set the left as the master.

After listening to all the JL's and reading about multiple subs vs. single subs I just felt that two F113's placed right next to each main made sense. I ran this by a factory rep and he said either two F212's or two F113's in my room should work well. Two F212's were out of the question.

In the demo room the differences were minor until you started running into the 90db range and this is where two F113's started to shine over the one F212. Just a stronger grip over all and a little more slam. They were both crossed at 80hz, eq set to zero on pre with -3db on 25hz and lower. Volume was set to ref and the two F113's could have been dialed back slightly.

The stage these produce is pretty stunning so either way you decide should work very well.

Howdy Jp1208. So you ARE operating them in a Master-Slave configuration. That is interesting. Having not owned JL Audio before, I have often wondered what differences may exist if coupling one to the other as opposed to running them in stereo mode. Also, you (Jp1208) mentioned that you x-over at 80hz, and even 90hz. Personally, I have not liked the overall sound when setting any of my previous subs x-over points that high. I have generally set my x-over points at around 50hz to 60hz, and found that to be much more to my liking. I HAVE indeed run dual subs (of the same manufacturer) before. I've run 2 Velodyne FSR 18's, 2 Von Schweikert "Towers of Power", and 2 Sunfire True Subwoofers. All at different points in time. The big Velodynes were staggering and waaaaaaaaay too much for a two channels set-up. The Sunfires were friggin' terrible...I'm talking real hammered dog shit (only MY opinion), Muddy. Overblown. Distorted. Inaccurate. Shook the whole house but could never get them to integrate worth a darn. I dumped them quickly. The Von Schweikerts were probably the best overall pair of subs I ran in conjunction with a pair of Martin Logan Quest Z's. I'm still kicking myself for having gotten rid of them. Oh well, live and learn, huh? I always ran the pairs of subs in stereo, sending the left and right signals from my preamps, to each of the subs, respectively . Never used any sort of processor. Now here I am in 2013...15 different subwoofers later, and now it's time to try JL Audio. I suspect a pair of F113's might be a bit too much given my room dimensions?? But I'm leaning toward a single F212. Maybe? Haven't yet decided. My JM Lab / Focal Sub Utopia is really an awesome sub, but seems to be "out-paced", and "out-gunned" when used in conjunction with MBL 101e Mk2's. I loved what the JM Lab sub did while doing duty with my Martin Logan Quest Z's, but not so much with my MBL's.
Hence, my renewed "quest" for bigger, badder, more ferocious bass.
That having been said- any last bits of input from you fellow Audiogon members regarding which direction you might take things?
1 Fathom F212?, or 2 Fathom F113's in a master-slave configuration? (again, my room is 15'w. x 18'd. with 9 foot ceilings).
Thanks to all who have contributed input so far.