I have personal experience with REL, SVS, Rythmik and to a much lesser extent Martin-Logan. In my experience Rythmik has the best sound quality, though not by much, but if you have  a penchant for loud bass heavy music, they may not have the power you would need for them to keep up. SVS in my opinion is a great value and should be able to handle anything that you throw at it. REL sounds okay but is just not worth their price. Unless you need the auto correction, I would look at the "E" series instead of the Fathom. Magico, I have absolutely no experience but they seem like an awful lot of money for probably very little if any audible improvement. I would definitley want to do an AB comparison before I bought them.

Of all the subs that you have listed, I would pick the SVS. 

@m-db thanks for that bit of info on the tv show. I will have to check it out.

regarding the fleetwoods - they are solid. Just not bass impact performers in the 80hz - 100hz region. I want to hear that slap or impact here.  No one said they were but I crave this for me and the type of music I listen to  

regarding my carbon specials. I am asking them to do too much especially if I’m not willing to tune or walk them around the room as they should. Due to their size they have to stay visually appealing. I’ve used rew and I do get down pretty low but I have room boom and without some sort of eq or more room treatment the subs will just overpower.

Duke is being much too modest (as usual):

I have owned the fathom 113v2 with CR1 and the S510s. The companies obviously different philosophies. While JL's features are all about the frequency response, REL has videos suggesting positioning by way of impulse/timing in reference to the main speakers. That would be impossible with the fathoms. I am confused by REL's approach. Positioning subs to sync an impulse with main speaker would realistically mean the frequency response will not be optimal. Like Duke says, my experience is that peaks and dips and long decays are easily heard and measured.  Their difference are also reflected in preferred connectivity. With my (balanced) amp, I much prefer the ease of low level inputs to the quirkiness of hi-level used by REL. 

The fully automatic EQ included with the fathoms is powerful and does allow for  more liberal placement than the RELs. I. did have personal satisfaction of getting the mains and rels just so, to even out 40Hz and below, though. Ultimately I needed a crossover to flatten a 60Hz vertical resonance from my main speakers.

It is hard to know what features are needed for both particular people and particular rooms/speakers. 

low325, FYI, Devilles were props in, I believe, the first episode of "Just Like That." 

We managed to get much better performance from a down firing REL Studio III by locating it on its side in the rooms major mode and using L&R processed low level signal from an early remote controlled Velodyne DD. While this improved its presentation noticeably it didn't equal the, at less than half the price Velodyne and its low frequency response never reached the manufacturers claim. 

I have Devilles and two REL carbon specials. I have turned the subs off for quite some time since I have had my Devilles. Now thats not saying the Devilles go low so dont believe the folks who are claiming this, LOL! Spending this much on ‘unique’ speakers makes the mind think amazing things, hehe. ;-)  was it the latest stereophille that measured them to useable 50hz in room…?)  

Back to reality, yes I, too, am (lazily) looking for a ‘solution’ to fix my low freq response in my room. For what its worth, I had other speakers before the Fleetwood and those loaded the room with bass in a way that integrated well with the RELs. I also had different amplification before, blah blah.

My options are finding something that will increase transients in the upper bass region, add DSP, or swarm like Mr Duke. I’m not ‘needing’ anything that goes below 30hz, a nice to have but not a quest…. Open baffle would be wonderful, but dont mind looking for more of a finished product than GR’s OB (hurry up Magnepan, jeez!!!) since I have a shared space. My wife allows me to play (god bless) so I must at least make it look decent.

Rel is the one sub everyone compares their product to especially on this site.Just about every post on this site when talking subwoofers references Rel

The above statement is not necessarily true...Definitely not just about every post about subs...

REL is way over priced for what you get.

There’s also GR open baffle subwoofers not mentioned in this post.

Take a look at Power Sound Audio, and as mention earlier Rythmik, very musical subs for the money with phase and other adjustments with Rythmik having multiple connection options to be considered also.

@audiokinesis, there’s something to be said about a subwoofer manufacture that gives advice on how to maximize a competitors subwoofer’s musicality and output with nothing but positive and constructive things to say and more importantly what to do to get there.

OP, I admire you taking on using REW also for better subwoofer output and pleasing sound.

Assuming competent subwoofer design, by far the most audible issue in the bass region is uneven frequency response caused by room interaction. The audible effects of room-interaction peaks and dips on a sub are much greater than the audible difference between two high-quality subs. So if you’re going to solve the problem that matters the most, that would mean addressing the in-room frequency response.

You might consider keeping your two SVS subs and adding two more subs, then distributing the four subs asymmetrically around the room, such that each is a different distance from the nearest corner (and maybe have one of the four in a corner). This will result in each sub generating a significantly different room-interaction peak-and-dip pattern at any given location within the room. The sum of these different peak-and-dip patterns will be smoother than any one or two subs would be, and "smooth" bass = "fast" bass.

As a ballpark rule of thumb, the in-room bass smoothness increases proportional to the number of bass sources in the room, provided they are in acoustically dissimilar locations. And this improved bass smoothness holds up throughout the room. In contrast, the in-room bass smoothness of a single equalized sub (no matter how capable that sub is!) only holds up in a small area, outside of which the frequency response is likely to be worse than it was before EQ.

The net result with a good distributed multi-sub system is that you hear more of the low-frequency information which is on the recording, and in particular more of the spatial information, because there is less "masking" imposed by your listening room’s "small room signature" in that region. Imo this is conceptually consistent with a loudspeaker like the DeVille, whose well-controlled radiation pattern likewise results in less imposition of the listening room’s inherent "small room signature" atop the venue acoustics on the recording.

Duke

subwoofer manufacturer

+1 jtcf and emailists.

Did you use the presets and the remote volume feature often?  

A Double Bassist I'm constantly changing my subwoofer systems volume and its six customized EQ presets via remote control on a majority of recordings to suit my personal taste.

Aren't Magico's Asub adjustments computer accessed only?

Whatever you end up with I recommend sticking with something with DSP.Or just add a third sub of your choice to the two existing SVS.Dialing in the Q,setting the slope,and controlling the room modes are vital to fine tuning.

Seaton sound Submersive HP 

Rythmik F12

I have Thor hammer in pool house. Six pack stack rel in main system.

Thanks all for the posts. Helpful indeed. m-db I've had the SVS-3000's for a couple of years and have some familiarity with REW though far from an expert. Wish there was a book REW for dummies! I'm leaning toward the Magico Asubs but there are no dials. All software controlled with built in DSP through their software and REW. Anyone have experience with Magico Subs??

Is this that guy that drool all over cabin every time get a new gear? Get sub that go deep not rink dink sub you must pay plus $4000 stay away bargain want be sub.

foolish1, is this your first subwoofer?

You mention assistance if you went with the Magico. How do you feel about setting up a subwoofer? 

Popular brands get popular, often, because they’re excellent. But that doesn’t mean they remain the best value. Let's agree to disagree. You can think I'm silly or stupid and I'll just think you're smug.

Yep silly you indeed....Rel is the one sub everyone compares their product to especially on this site.Just about every post on this site when talking subwoofers references Rel and for reason..you pay for that not the name...

@missioncoonery Oh, I’m sorry. I forgot that no one ever pays a premium for a name. Silly me indeed. Thanks for your help. 

OP, you DO pay a premium for REL, and some just think it's worth it. I like my REL. But numerous good subs are out there, and you want adjustable phase, which REL does not provide on most of their models. That was what diverted me from REL for further subs.

You don't pay a premium for the name,,that's just silly at best. Whst you pay for is the best subwoofers in its respective price point made...IMO

Rel (any of their carbon based subs)-Biggest concern is no phase adjustment.

I have a REL 328 and like it a lot. BUT the lack of phase adjustment is the Achilles' heel for anyone wanting to dial in the sub.

The direct-servo Rythmik line is excellent and completely adjustable. And you don't pay a premium for the name, as you do with REL. Better value.

REL are the easiest subs to integrate perfectly despite not having a variable phase.  i had jl audio and martin logan dynamo and after months the integration still had occasional issues like peaks, midrange coloration from enclosure resonance and hard sounding lack of quality.  

Note, this is for 2.2 channel music.  HT is a different animal.  

RELs have solid non resonating enclosures.  Follow their break in and positioning guidelines and you can get an excellent integration in a few days.  

RELs play low in room despite the specs and have plenty of power.  Properly adjusted they offer depth, punch and do not color the midrange and are fast and non lagging.  

I believe they are not so critical about phase adjustment because they are so fast and have a down firing passive radiator (my T9is)  that balances the sound pulses.  

finally i like the sound quality of their bass, a nice pleasing tone that is not too dry and tight or loose and flabby.  

Add Vandersteen to your candidates!

https://www.vandersteen.com/categories/subwoofers

Also I have never had a reliability issue with my ?carbons.  I have not heard god things about JL audio reliability, but have no personal experience.

For REL pricing PAV in Chicago was good to me..

I am very happy with REL Carbon Special and Carbon Limited subs.  I have a pair of each in my two systems. They are not located inside or right beside my speakers, as I found better blend when placed off to the sides with one angled in more than the other.  This helped blend into the room much better.  I replaced Paradigm studio 15's, which were very low and deep, but the REL's blend and support my stereo much better.  I Found the phase switch adequate but of course did not have variable to play with  Both of the Carbon's have great resale.  The Paradigm not so much.  I have also heard those SVS and the app and control is cool, but I thought they did not disappear nearly as well.  With them you need the app to turn them down when the are to much.  Once dialed in I never mess with my sub controls.

I’m a big fan of Velodyne.  They sold the subwoofer line and it’s now being manufactured and supported again.  I’m using 2 of the 10” DDplus in a very large space and up on stands (which means it doesn’t get the boundary gain being on the floor, but it more articulate) and still provides amazing bass. 

SVS is okay but how about Funk Audio? They make several models.