Who makes the best subwoofer for music? REL or JL AUDIO? REL uses High level, JL AUDIO low level with EQ. Which will be better for music. 
For best sound with a sub you want to use a highpass. It can be in the preamp (most two channel preamps don’t have one) or external. 

 The JL “E” line of subs has a highpass built in but no EQ built in. The Fathom line does not include a highpass and you need an external one but has built in room correction. 

Without room correction you will have dips and peaks in the bass. 

With that being see I have two E112 subs that have both broken twice and need repaired. While JL did fix them once for free under warranty and once at my cost (pretty cheap to fix honesty) I can’t recommend them as a brand. But they sound great for music. 
I've owned both....dual JL Audio F110 v2 with CR1; JL Audio F112 v2, dual REL Carbon Limited, and I currently own dual REL G1 mkII subwoofers. I submit like most things in this hobby it comes down to personal preference.
Martin Logan also makes some very musical subs so you might look into them also. My 212’s came with room correction. 
If I had to choose only between your two highlighted brands : REL

If I can select a best-of-breed choice that are true contenders and no pretenders : ATC or VANDERSTEEN
Between those two, I prefer JL.  My new favorite though is Perlisten.  I think they make a better sub than both as the DSP is best on market that I am aware of.  
IMHO...More is better, ie you're better off with multiple subs arranged to manage room modes than looking for 1 mega buck sub.  With multiple subs each one only carries a fraction of the load.
There is nothing special about the Perlisten subs, just marketing BS. None of them include a high pass filter, a fatal mistake.

I have also been turned away from JL Labs products due to multiple reports of liability problems. I have personal experience with one failure.

There are many fine subwoofer drivers out there now and many digital processors with fine bass management capability. The best way to deal with subs is to get a processor, separate amplifiers and passive subs. The key to low distortion is using large and multiple drivers keeping the excursions short. With bass management sealed subs are best. As long as you have the power you can make the sub do anything you want. 

You would be surprised how inexpensively this can be done. Parts Express has great subwoofer kits that anyone with two hands can build.
As an example; Four Dayton Ultimax 12 sub kits + a MiniDSP DDRC 22D + 2 QSC QX7 amps = $3400.00 plus some elbow grease. 
A single JL Labs Fathom 113 is $5000.00. 

Great thread.  I've wondered about the same question.  Having only owned a REL (528SE) and in the market for two subs, this is great information.  Reliability is important as shipping subs back and forth to the mfr for repair is not something I'd want to do.  My use is for music only.
I had a pair of JL Audio E-112s, very fine subs but I couldn't take advantage of the built-in XO...I replaced them with a pair of REL S/510's...and was able to get much better integration with my mains using the high level inputs. 
Appreciate all the input. I have a REL S2 and am upgrading so I wanted to know which way to go. Looks like I'll stick with REL. The Carbon Special looks like the one. 
Lots of rel are made in China ,except upper line  over$2-3k range 
on average , why no adjustable app ,? 
SVS makes  the excellent Ultra 16,
As well as the  3000 SB  that are every good if not better in their price class.
SVS have a great app for all adjustments ,Free shipping, 45 day audition 
if not happy they even pay return full refund ,5 year transferrable 
warranty , does Rel or ,JL do this -Not that I know of ,
And  a bunch of Excellent reviews !!

A close friend of mine just dumped SVS and switched to a pair of REL Carbon Limited. REL comes with 60 Day home trial and free shipping and returns!
That says nothing a empty statement- they sold there SVS sub ?,Svs has   Over 8 models , and both the3000SB,4000 and ultra 16 SB are loaded with accolades around the world .I have had both rel and JL audio and dumped them which were $1200 or less it all depends what model good and bad in all , I love  the SVS  sub app all adjustments from your phone or tablet.
SVS is out. They are nothing but a big boom box. REL or JL AUDIO are the only consideration. 
I hav Jl audio,  rel  and M&k subs in my systems . All pairs.
IMO the sub choice  depend on the speakers you are matching them with . I use my Jl Gotham’s v2 pair with my magico M3 integrated with a cr-1 crossover and the integration and blend is seem less . The rel s812 pair  I use with my Charney horns using high level inputs . Good integration. Without an adjustable phase I feel  the integration is very good but not perfect . The ease of set up though is beyond compare .
 Took me with the help of bass guru Barry the Sounddoctor months the get the Gotham’s tuned in to perfection to the room with thr m3 . The Rels I could do it in an evening. They  sounded decent just plugged in  lol.
The M&k x12 pair I use in my home theater . Thundering sound effects . Set up using Dirac.
Each sub IMO is a diff beast . To compliment full range accurate speakers Jl audio,  if you take the effort will win. For just adding bass to a limited range speakers with ease rel would win.  Purely my experience. I have been a rel faithful from their st series . 
I have owned dual SVS SB15 and SB16 Ultras, HSU, JL Audio, Martin Logan Depth and REL subwoofers. I prefer the REL G1 mkII over every other subwoofer that I've owned. JL Audio subwoofers hit harder, but to my ears, in my room/system, no other subwoofer improved everything across the audio spectrum like REL. You can't hear my G1s when they're on, but turn them off while music is playing and I just shake my head.
I just switched from my Martin Logan Force subs and picked up 2 REL subs after demoing REL and JL Audio.  Extremely happy with the upgrade.
My JL crapped out. Been meaning to send in the amp to fix for $400 but haven’t gotten around to it. I hear it was a round of bad caps in the 1st couple years models. 
I have a REL and like it a lot, but I chose Rythmik because it's good a great reputation and is a servo sub that is eminently adjustable.
I know you are inquiring about REL and JL Audio, but you might consider looking at Rythmik Audio subs. They use servo driver technology. I have their FV18 for music and home theater. It's fantastic for both. 

No servo subs. Ancient history.  REL and JL AUDIO info only. Looks like JL has the output and power, REL has the finesse.  For the same price as a JL F110 V2 I can get a REL CARBON SPECIAL.  REL is made in China though. That for me is a big problem. 
I also sold my REL S812 and bought 2 Rythmik G22s, much better low bass, tremendously better integration, just as tonally accurate - or at least similar, but most likely due to the servo, a little less immediate.

Regardless the Rythmiks are a really nice step above the RELs for music, but I have different subs for HT as the G22s are just too clean and refined for those needed sonic movie thumps.

P.s. jeffvegas, I used to think like you, untill I did an A/B comparison. To each their own.
Heard Rythmik, weak bass response.  Lack of dynamics . Like all servo subs I've heard there seems to be a delay in the sound, like the sub is CORRECTING the signal AFTER it happens. Started this thread as a REL and JL AUDIO comparison.  Not bashing other brands. It's a free country.  Buy what you want. For me it's REL and JL AUDIO. JL AUDIO might win because it's not made in China. 
"sold my REL S812 and bought 2 Rythmik G22s, much better low bass, tremendously better integration, just as tonally accurate - or at least similar, but most likely due to the servo, a little less immediate."

just based on what you've stated, 2 subs replaced one. Regardless of brand, it SHOULD sound "better". More of whatever brand  sub is going to be more convincing than 1 "premium" brand sub.  

I just upgraded to a JL, heard most of the brands in this thread. The thing that won me over was their DSP, they are built like tanks and weight just as much. Solid. But I wouldn’t have minded a Rel or Martin Logan, I brought before the new KEFs came out and would have liked to hear them. Any one here do a swarm of mini subs yet? 

A swarm with mini subs would be interesting, especially for an irregular room. 4 duel driver 6.5” kefs (8 drivers total) subs would have a lot of surface area.

 In my head I alway like big drivers for bass but I know that is not science based… and it comes down to box size and efficiency. 

Anyway back on topic. Even though Rel subs are made in China I bet they have less failures than JL which probably uses Chinese electronics in a U.S. assembled sub (just assuming and I have no actual knowledge). 

I would also love to know if it seems like JL Audio’s fail more simply due to more market saturation, but my reliability experience has not been good. 
So interestingly enough, this is the exact dilemma that I have been having. I have been torn between the 2 brands for the same reason and have not been able to actually buy one over the other. What I find interesting, and maybe others can help explain, is the large power difference between the amps of the two brands. Yet both have great bass, just different style bass. 

I would not worry about the rated power and look at total DB output if using in a home theater application. For music who cares as you will not be at the limit.

I would guess you are seeing the difference between the efficiency of sealed vs passive radiator. The sealed box of the JL will require more power. Also keep in mind going from 800 watts to 1600 watts is only worth 3db and when not driven at the limit will not matter.
@jeffvegas --

I'd rid myself of brand-focus and gadgetry and go with the DIY-advice of poster @mijostyn above. Let physics have their say, and when you buy separate components (certainly electronics) reliability usually sees a clear boost. Cheaper as well.   

If DIY is a no-go I'd go with the likes of a duo or quartet of PSA's S1512. Very high quality subs with great pro drivers and good ICEpower amps - way cheaper than both REL and JL Audio to boot. 
Have *both* REL and Rythmik and have compared extensively, too. Both are good. Rythmik has no weak bass response or lack of dynamics in my room and no delay in the sound. Jim Salk, a top-notch speaker maker, uses Rythmiks in his custom subs.

Still, rooms are a big factor and of course so is subjective perception. Good luck with your REL and JL AUDIO comparison. 
I own both brands. As a reliability issue for JL, that was with the older E Series. I believe it was the volume pot or something basic. The V2 are really reliable and in the F series they have 80% more adjustment nodes than the V1 series. The issue with JL Audio VS REL is cost. With REL you can get a smaller T series sub with the Speakon connection and it is as smooth as silk. It looks like the Carbon series in REL is like the ESeries in JL with a Speakon connection. With JL F110 series you have the same specs with a cheaper price and a smaller foot print. If you want the Speakon connection then go with REL. If you are going RCA connections then go with JL. The best system is two JL F110 subs and the JL CR1 crossover. It lets you dial in the perfect crossover point on your subs but more importantly your main speakers. The F110 have 18 point room correction. They play at the same frequency as the bigger RELs do but at a cheaper price, a smaller footprint, and with one driver. So in a nutshell it’s REL at a cheaper cost at the lower end. Since you are going to $8000 I say go with the JL. Regardless of brand pick up a JL CR1 crossover as long as you are using a separate amplifier. At these price point it’s JL Audio. You are getting way more bang for your buck. No pun intended. The F series is so good you will not look back. As long as you do not need the Speakon connection. The JL is so good I have not even needed the room correction. 
I tested with 2 S812s (borrowed one from my local dealer) because you are absolutely correct 1 vs 2 would not have been a fair comparison.

@hilde45 and @jeffvegas
My experience too, my Rythmiks had better bass (much lower than the REL S812s) and I still say cleaner bass as well and there was certainly no delay with the servo (at least not audibly) perhaps due to the fact that I had so much more control over the setup of the Rythmiks than the RELs. (REL’s never did integrate as claimed) But I agree with jeffvegas that I think that the dynamics were a hair better with the RELs.

Always find these discussions interesting, there are so many factors which guide us to our solutions. The differences in equipment, the amount of money tied up in each component, and especially the room size and acoustics. So many variables... that is why I still prefer my brick and mortar dealers. -- wish there were more!
There is no question about this ….REL.  if you can play 2 and place them in the corners for best sound.  I have a pair of S2’s and they changed my sound significantly.
I personally like SVS. I thing they are well built, economical, and do a great job. 
@james633, bigger drivers of the same caliber are always going to sound better and that is science proven. There is a simple reason for it. As the cone excursion increases the suspension becomes progressively less linear. It gets stiffer until it can't move any farther. This distorts the waveform. Larger drivers do not have to move as far to move the same amount of air resulting in less distortion for the same output level. There is a limit however. As the cone gets larger it becomes more difficult to control and in many instances starts to wobble. You can see it happen with a strobe. The largest anyone has to go in a home installation is 15" If more power is needed the go to multiple drivers which accomplishes the same thin as larger drivers, shorter excursions. With the right size drivers servos are not needed at all. It is easy to keep distortion under 0.5%.

There are issues with the use of subwoofers that manufacturers won't mention primarily because they can't deal with them or are afraid that the increase in price will knock them out of the market. 
The first is the use of a high pass filter or rather a complete two way crossover. Taking the bass out of the main speaker dramatically lowers distortion in low frequency drivers that operate well into the mid range. You can tailor the response curve of the main speakers and subwoofers to match perfectly and you can take the crossover point up higher without difficulty. Next is a critical issue that they never mention. The impulse from the subwoofers and the main speakers has to reach your ears at the same time. You want to listen to one bass drum not two bass drums. This can not easily be achieved by positioning the subs. The problem is that subwoofers are most efficient in corners and against walls, up to 6 dB more efficient requiring much less power which is vitally important if you are using DSP correction. Most people position their main speakers away from the wall placing the subwoofers 3 to5 feet behind the main speakers. That is a 0.3 to 0.5 millisecond group delay. The easiest way to fix this problem is to digitally delay the signal going to the main speakers. Phasing and time correction are impossible to do accurately by ear but you can measure them with a $300 microphone/measurement program or with a comprehensive room control system. If you want to fix the group delay by moving the subwoofers or speakers then all you need is the measurement microphone. You will just have to accept the fact that your system will not be as efficient as it could be but if you do not have digital facilities this is the only way you can do it. Comprehensive room control preamps with bass management programs are the best way to go. New units are coming along all the time and some of them are not very expensive. MiniDSP, DEQX, Anthem and Trinnov are a few. 

There is no commercially made subwoofer that will provide state of the art bass out of the box. The system I describe above will out perform any subwoofer named so far in this thread and not by a little. I will not buy any more commercially made subwoofers. There is only one that meets my requirements and it is $36,000.00. I would need four of them 🤢 Discounting my labor I can do pretty much the same thing for $15,000.00 in drivers, amps and enclosure materials. 

I have no relationship to Audio Kinesis but I think most here would be better off buying their swarm system.  

If you have one of the above subwoofers you can do your main speakers a favor by soldering capacitors in series with the inputs of your amplifier.
The value is calculated with this equation Fc = 1/2piRC or C = 1/Fc2piR Fc= cut off frequency, R=input impedance of amplifier, C= capacitance in Farads. So if your amps input impedance is 10K ohms and you want a cutoff frequency of 100 Hz  C = 160 nF.   You can get the caps from Digikey. I forgot to mention that this is a 6 dB/octave filter.


thanks for the information and I agree. 
Integrating a sub without a highpass is a waist of time IMO and causes more problems than it fixes. 

The resistor idea is a good one for sure. Though I think a DYI sub with highpass and measurements is way over a lot of peoples heads (mine included). Understanding and doing are two different things. Baby steps lol. 

Any thoughts on a direct to consumer subs like JTR Captivator RS1. I heard about it on Audioholics and it looks interesting (great measurements).  Kind of a “DIY” value done for you. It would need a proper highpass of course.
Heard SVS. Junk. Nothing more than a boombox. I need quality not quantity.

Almost there. 
Having owned both here are the pros and cons-

JL Audio
+Powerful, nice sounding bass with deep impact
-Cabinet resonance colored the midrange of my monitors- a deal breaker
-Difficult integration even with high level inputs and continuous phase control and REW measuring.  after over a year the integration still was not perfect
-High level snap in connector difficult to install and somewhat loose.  

+Nice sounding bass, more subtle and very fast and musical.  Plays flat to 20Hz in room.  
+Solid cabinet with no resonance- midrange from monitors is perfect- no coloration.
+Extremely fast and easy to integrate, weeks vs. years.
+Level and crossover controls have "click steps" to document and adjust the settings.  
+High level input cables are long and of good quality.

Keepers in my audiophile system.    

I alternate between KEF LS-50s and Magnepan .7s for my primary speakers. Most subs I've tried make low tones but they sound wooly, slow, and flabby compared to the primaries. The REL T/7x in my listening room is an incredibly good match for both speakers. Fast, well defined bass,with adequate dynamic range and output level in my situation. Bigger room, bigger speakers, obviously I would double up or go with a higher-end offering.