How do SVS subwoofers compare to REL?

Woofer "speed" is a silly term that should be declared useless as it exists only in the minds of lazy reviewers and Bo. I use 2 RELs I bought at different times…both from the same era I think, and both cost around 200 bucks each used on Ebay. A highly recommended route to bass enhancement…be patient, and buy ’em used. A Q150e and a Q108 MK 2…both require careful matching to the main speaker’s frequency drop off, sensitive placement (they’re easily offended) and output adjustments here and there. I use them wired equally instead of stereo because I stick the 108 in a window to my deck sometimes for Al Fresco listening. Plus hey…they’re different. I make my own cables for them (Canare quad stuff with AQ spades and the required Speakons in the "high level" inputs). Recently I wreaked havoc on them by buying very efficient speakers (Klipsch Heresy IIIs) to match with my 12 watt per side single ended amp, so since the RELs get less signal I had to mess with them a bit to get ’em right again. Plus the Heresys surprisingly have no deep bass (58hz and it dies). Worth it though...I don’t use DSP because I don’t seem to need it, but I bought a Schiit Loki and it works great for a little boost or cut here and there, although most of the time it’s out of the loop, so to speak. The amazingly transparent Loki is also "el cheapo" which seems to be a theme in my rig, but the whole thing sounds astonishingly good.

I’ve used an Antimode, but haven’t ever used a DDRC. In principle there is no reason why any line-level DSP couldn’t be used between preamp and SVS subwoofers. One would just leave the subwoofer eq flat (as shipped) and let the outboard DSP unit do the room correction.

The biggest difference I see between the two from a very quick skim is that the Antimode addresses the low frequencies, the DDRC corrects the entire frequency range. If you are happy with the response of your Maggies then DDRC would be overkill. In my opinion, the frequencies addressed by the Antimode are the most problematical anyway and far and away swamp most higher frequency response anomalies.

I will say as a matter of my personal prejudices and not in anyway trying to make a statement of absolute fact, I much prefer to use acoustic treatment (absorption, diffusion and bass trapping) as a necessary first step to address room geometry effects and only then apply DSP, and the minimum DSP necessary, after experimenting with speaker placement in an acoustically treated room. The only DSP I apply is to the range addressed by the subwoofers.

But then, I am a guy who still thinks analog sounds better than most digital, even though digital is definitely getting better and I do listen to my share of digital content.

@steve_zettel thanks again! I noticed your mention of miniDSP and looked up this page: https://www.minidsp.com/products/dirac-series

EDIT: The miniDSP products look too complex for me right now. I'm just learning about all this stuff. The Antimode 8033 is really simple to use.

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Original post:

Anyone care to comment on how a product like the miniDSP DDRC-22 compares to the DSpeaker Antimode 8033?

I found a couple related forum discussions (in German) which help me understand a bit, but I would appreciate any further advice or recommendations.

When should the miniDSP DDRC-22 be considered as an alternative to the Antimode 8033?

Here’s a google translation of one:
http://www.hifi-forum.de/viewthread-72-5677.html

the two options you mentioned are quite different. An antimode AM 2.0 does not make automatic corrections in the entire frequency range, but only up to a maximum of 500 Hz. In the frequency range overlying adjustments to desired target frequency response can only be made manually. A DDRC uses DIRAC and corrects the entire frequency range, allowing arbitrary target frequency responses. In addition, DIRAC can also correct the time response (ie the step response) to compensate for turnouts of turnouts / chassis. Therefore, I would more credibly trust the DIRAC-based solution.

However, the DDRC-88A you mentioned is an 8-channel analogue solution. If I understand your description correctly, but you would calibrate only the fronts, ie you would einschleifen the DSP between the switch box and the power amplifiers. Then you only need an analog stereo DSP such as a DDRC-22A.

The other discussion:
http://www.hifi-forum.de/viewthread-35-69208.html

@willemj: You are correct. There are three available manual eq bands. No auto eq, so some other means of measurement are required. I use StudioSixDigital AudioTools app and their iTestMic (http://studiosixdigital.com/) or REW and a minidsp.com UMIK test mic for determining in-room response. The SVS iPad app makes adjustments very easy and allows adjustments from the sweet spot with a graphical representation of the amplitude and Q of the cut or boost being dialed in.

I use two bands to knock down the two most prominent peaks in my room and one band to raise the lowest bass roll-off. Plenty of headroom in the powerful SB16 Ultra amp to tolerate a reasonable amount of boost in the very lowest octave.

And I think you are absolutely right about the Ultras being best suited for larger rooms. I can't imagine being in a small room with one, let alone the two Ultras I have in my largish volume. Then again, there are folks who really, really like sledgehammer bass (check out the insane auto sound bass videos on Youtube for a sample).

@lowoverdrive: You are welcome. I can't speak to the PC-2000 but I do understand your concern about footprint. The SB16 Ultras are basically a 19 to 20" cube. A very attractive black cube in their gloss black finish, but there is no overlooking them in the room, unless you hide them behind something or use them as end tables. I had a piece of dark gray smoked glass cut to size to place on top of each sub to protect the finish so I can put something on top of the subs and not worry about marring them. And I am very glad I opted for the SVS isolation feet to decouple the subs from my hardwood floor.

SVS have super customer service, are very responsive with questions and have a great trade up policy, along with the in-home trial period and free shipping.

Good luck with your subwoofer hunt and let us know how it works out for you.

@steve_zettel  thanks. I have to say I am leaning toward SVS subwoofers. The Sumiko also look interesting to me. But SVS's 45 day free trial (free shipping both ways) makes it so easy to give them a try first. Unless I learn something new in the next few days, I think I'll order something from SVS.

@axememan suggested the PC-2000. Does anyone else have thoughts on the cylindrical subwoofers. I believe they are ported. But the compact footprint is very attractive to me and would work well in my room.

I had a quick look at the SB16 specifications. From what I can see it can do some basic manual equalization, but it does not measure response, let alone correct it automatically - but correct me if I am wrong. Beyond that, I think is is an enviable subwoofer for people with really large rooms.

Here is the URL of the SVS subwoofer top-level web page:

https://www.svsound.com/pages/subwoofers

SVS do a good job of explaining their line and the hierarchy within the line of subwoofers.

Most folks like sealed subs for music-only or music-first, home theatre-second systems and ported for increased output and lower roll-off for home theatre systems. That said, this is very much the conventional wisdom and as such should be subject to your own preferences. I

n my two-channel music only system I can't imagine needing more SPL or deeper extension than the sealed SB16 Ultras provide, and I do listen to pipe organ, EDM and trap in a large open-plan home. The system sees about 9000 ft3 of volume and the Ultras have absolutely no problem pressurizing the open area.

Hope this helps.

As for DSP in subwoofers, it is used for two things and it is important to distinguish them.
1 As a means to shape the frequency response (boost the lowest frequencies), and as a way to manage the demands put on amplifier and drive unit. Mostly, this is done by reducing the deepest bass output at higher volume, to limit distortion and potential damage to the driver. DSP can also be used as a more refined digital crossover.
2 To measure and then correct in-room response. For this, the system has to measure in-room response with a test tone sweep and a calibrated microphone, construct a correction curve, and then apply that curve.

These days, many subwoofers do 1) and some also 2), such as the bigger models by Velodyne and B&W, but rarely as well as the Antimode 8033.

Found some answers in this review:

http://www.avrev.com/home-theater-loudspeakers/subwoofers/the-svs-sb-2000-subwoofer-review.html

There are differences and advantages to sealed and ported designs. According to SVS, "sealed subwoofers typically have a smaller overall cabinet size and footprint, allowing easier integration into the listening environment with minimal visual impact to the décor. A properly designed sealed subwoofer will typically exhibit less phase rotation, lower group delay, and reduced ringing in the time domain. These characteristics make the sealed subwoofer a natural choice for critical music applications, and are typically described by enthusiasts as sounding tighter and more articulate, with less perceived overhang.

A sealed subwoofer naturally has a shallower roll-off slope than a ported subwoofer. SVS takes this concept one step further by employing sophisticated DSP equalization to tailor the overall shape of the frequency response and roll-off slope, in order to take maximum advantage of available ‘room gain’ so common in small to mid-size rooms. The end result is much deeper in-room extension than the quasi-anechoic frequency response would otherwise suggest.

With each successively deeper octave, cone excursion quadruples in a sealed subwoofer in order to maintain the same sound pressure level. In addition, the equalization required to tailor and optimize the quasi-anechoic frequency response consumes amplifier power. As a result, a sealed subwoofer will typically have considerably lower dynamic output limits <40 Hz than a larger ported subwoofer in the same family/price range.  

In a ported subwoofer design, a relatively large enclosure size is required in order to achieve both a deep system tuning frequency, and sufficient port area to minimize chuffing artifacts at high drive levels. A larger enclosure also greatly enhances system efficiency in the deeper octaves, with no need for additional EQ boost to achieve naturally deep extension.
   
The result is 2-4X more peak dynamic output in the 18-36 Hz octave as compared to a sealed subwoofer in the same family/price range. This makes the larger ported SVS subs a natural choice for system applications with larger rooms (where less room gain is present) and IMAX-like playback levels, particularly on demanding Blu-ray action and sci-fi movies with strong LFE tracks."

Review of the Sumiko S.9

https://hometheaterreview.com/sumiko-s9-subwoofer-reviewed/?page=2

When you consider the actual improvement it can deliver to an audiophile two-channel system (especially one employing small to mid-sized tower speakers or large bookshelf speakers), how little effort it will take on the listener’s part to gain that improvement, and that it won’t detract from the sound quality of the main system, it’s probably one of the best buys a subwoofer-less audiophile could make...

and, Sumiko compared to REL:

my experience leads me to suspect that few, if any, unbiased listeners would express a clear preference for one of these subs over the other.

Is the DSPeaker Anti-Mode 8033 recommended with the higher-end SVS subwoofers which have their own DSP?

@bunnkmpharmd

On the subject of subwoofers for Maggies, has anyone compared Magnapans own DWM bass panel to those excellent subwoofers made by other companies?

Even my Magnepan dealer did not recommend the DWM bass panel because (if I understood correctly) it is designed for the smaller Magnepan speakers which do not have a bass section. I was told that it would not add anything to the 3.7i series. I guess it might not add anything to the 1.7i either. For those, you want something more like the options discussed above in this thread. That's my understanding anyway. Correct me if I'm wrong.

Here's a subwoofer I haven't seen mentioned in this thread:

B&W DB3D SUBWOOFER
DB Series Dual 8" Powered Subwoofer

Any thoughts on it?

On the subject of subwoofers for Maggies, has anyone compared Magnapans own DWM bass panel to those excellent subwoofers made by other companies?

@steve_zettel

The SB and PB4000 share the same DSP and app control with the SB and PB16 Ultras -- three parametric eq bands, three presets that can be customized by the user, real time gain adjustment. The only thing they won't do is play a test signal and auto-calibrate themselves, but with the flexibility and control of the app, tuning the SVS subs from the sweet spot without having to get up to make adjustments is a piece of cake.

I'm new to this stuff. I found the above paragraph interesting but also a bit confusing. Can anyone help me understand the SVS model hierarchy?

It looks like the SB/PB-16 Ultra is at the top -- 16" and 1500W.

Is the difference just that the SB is sealed and the PB is ported?

Then there are the SB and PB 4000's next in the hierarchy, it seems. I guess they are just a bit smaller (13.5") and less powerful (1200W), but otherwise the same (based on what I read above).

Below that are the SB and PC 2000's. How do they differ from the 4000's? Is it just driver size and amp power again? Or do the 2000's lack the DSP and app control mentioned above? Also, what about input options? I can't seem to find any pictures showing input options for most of these subs.

I also see a few other models such as the PB12-PLUS. Not sure where they fit in the hierarchy. Are they older?

It seems like most here prefer sealed subs for music. Is that correct?

I also like the look and the size of the cylindrical SVS subwoofers (such as PC-2000), but it isn't clear how they compare in terms of sound.

@jbhiller

I’m using a Sumiko S5, which is really a REL T5–as I think the companies are one in the same.

That's an interesting option.

I'd like to hear some opinions on two of the Sumiko S5 for my room & the Magnepan 1.7i speakers. (I ordered the speakers but I will not have them for a month; built to order.)

I do plan to add an Antimode 8033, but I will probably try the subwoofer(s) without it first.

@icanskate

PSB subs in my experience have a great synergy with Maggie’s.

Which model PSB sub would you recommend with the Magnepan 1.7i's?

Yes, for the most part, we do agree. I am not opposed to large woofers per se, but have had very good success with a single Rythmik F12SE with multiple main speakers. I would love to get another one of them and use it to help tame room modes. Subs with larger woofers would still be an option if I had a large room and needed that amount of displacement to achieve the output I desire. When set up properly in that case, I would see no reason that 15 inch and larger subs would sound slow. IMO, another factor not often discussed when setting a subwoofer up in a room is getting the phase between the mains and sub correct. When that is not correct, a sub never truly disappears in a room to my ears. 

Indeed and I think we effectly agree. I agree that there is little or no useful music signal below 25 Hz, and to be sure, for this and other reasons I am not a fan of huge woofers either. What I tried to say is that the issue of setting subwoofers up properly is largely to deal with the room modes.

What I did was compare apples to apples. That is my point. Most well designed 10 inch subs are capable of 25 hz. How much music is occurring below that frequency? Why would a 10 inch sub sound faster than a 15 if they are set up properly? My "definitions" above would be factors used to set up the sub properly. As you said, your 8 inch subs didn't sound fast until you set them up properly. I suspect the same would be true of a 15 inch sub, when set up properly.

It is true that under those conditions you have excluded a lot by defining it away, but in reality big drivers are likely to go deeper. That was my point. However, I am not excluding the possibility that big drivers are flabby and not as accurate. They would certainly need more control from a powerful amplifier. My own subwoofer (B&W PV1d) has two opposing 8 inch drivers, and is reputed to be 'fast'. Yet, without the room equalization that I later added this sub did not seem 'fast'. Originally it was certainly woolly and boomy and a problematic match for my ultraclean electrostats.

 I suspect that part of the explanation for the observation that big woofers are slower may therefore be that they potentially generate more room modes.

If the subwoofers are playing at the same level, in the same room/same location, with the same extension, and with comparable levels of distortion, I do not see how this can be possible.

I really think ’speed’ is not a property of the subwoofer driver, but of the room acoustics. If you look at waterfall graphs of low frequency output, you can see that the lingering of some low fequencies is at room modes. Deal with those, and your ’slow’ subwoofer suddenly becomes ’fast’ (been there, done it). I suspect that part of the explanation for the observation that big woofers are slower may therefore be that they potentially generate more room modes.
As for subwoofer design, I guess that everything else being equal sealed enclosures are more beneficial for music than vented ones, with designs with passive radiators somewhere in between. Vented ones are often preferred for HT and massive explosions (if that kind of movies is what thrills you) because they can go deeper and louder. SVS offer both designs. The Audioholics forum has many detailed discussions and measurement data.

I actually had the Audio Kinesis Swarm in my system and compared it against my dual Rythmik F12G's. The Swarm wasn't worth the extra cost over the Rythmiks. 

@lowoverdrive 
Search YouTube for speaker demos at the major shows that incorporate a subwoofer. 99% of those demos choose a REL. 

@bo1972 - I had the impression that SVS and REL are both fast response.

Does anyone else agree that REL and/or SVS are inferior in timing and speed? That's news to me if true...

Thanks

I sold Rel for many years of time. I sold them to clients and even to some friends. Most of them now own Monitor Audio subwoofers which are superior in timing and speed. This is an important part of a subwoofer.

The SVS are also rather slow in response. I did win each shootout against a SVS subwoofer in the last 8 years of time. 

A pair of PC2000 SVS Cylnder Subs will make you smile.

Hi lowoverdrive,
You have gotten some great feedback.
I have always associated SVS with Home Theatre Setups.

I included a link on the REL site to check out their recommendation on Sub Pairing for what you currently have. I would follow their advice at least for now and save yourself some $$ until you are ready upgrade to the next model Magnepans? 

Whenever you are ready, and want to continue to save some $$$ on the upgrade - The B-1/ B-2 are some of the best models REL produced. They are extremely musical. No longer produced but can be found on Agon and other sites from time to time.

Have Fun.
https://rel.net/speaker-pairing

One more thing- in talking with several so-called experts calling around before buying I was told by all that 10” or smaller is ideal for tight bass that is fast/quick and better suited for musical enjoyment.  You want the subs to keep up with your speakers in reproducing the music.  Larger subs go lower and match better for home theater use.  I have a larger room than yours and two REL T9/I subs did the trick beautifully.

I use a single REL T5i in a 12' x 20' room with Harbeth P3esr small monitor speakers.  The specifications indicate the Harbeths start to roll off at 75 hz.  Whatever the specs, the influence of the room will dominate the perception of bass.
I have somewhat limited options for monitor placement.  For optimal listening with my system in my room I pull out the speakers into the room and have more of a near-field listening experience.  Bass frequencies being much less directional (perceptually) allows me to move my sub around to get the most enjoyable results.  When I was setting this system up, I was on my hands and knees scooting the sub around until I liked what I heard.  It's not a symmetrical arrangement, but it allows the little T5i to adequately (at least for my taste) activate the room.  I may try DSP room correction some day, but I find that jiggling things around and listening works pretty good.  I would work with placement and room corrections before surrendering to the digital dark forces.
Keep in mind this works with my system in my room for my listening tastes.  I don't listen very loud, and I prefer smooth and buttery sound over bright and articulate.  My system sets up a somewhat miniaturized 
user experience, but it's all there – detail, clarity, soundstage, dynamics, and, most importantly, an intangible I'll just call musicality.

My experience with some of the equipment you are considering is a bit tangential at best -- I owned Magnepan 1.6 QR speakers for several years, but never tried to use them with subwoofers. I spent some time at friends home who used REL subwoofers very successfully with Spendor SP100 speakers. I currently use a pair of SVS SB16 Ultra subwoofers with KEF 207/2 speakers.

I think the SVS are a great value and don't give away anything to much more expensive subwoofers since the introduction of their DSP amplifiers, newly designed 16" and 13" drivers, and integration with a very intuitive app. The SB and PB4000 share the same DSP and app control with the SB and PB16 Ultras -- three parametric eq bands, three presets that can be customized by the user, real time gain adjustment. The only thing they won't do is play a test signal and auto-calibrate themselves, but with the flexibility and control of the app, tuning the SVS subs from the sweet spot without having to get up to make adjustments is a piece of cake.

I'm very pleased with the performance of the SVS subwoofers and how seamlessly they integrate with the KEFs.

@icanskate - which model PSB sub did you select for your Magnepan 1.7i speakers?

@hogarthd

...anyone that can point me to a thread about how to tune all the options beyond just the simple cutoff frequency on the SVS SB16 would be really appreciated (phase, etc).

What I read is that phase is important only if there is more than one sub. Set each sub to the opposite phase. It's not important which is which, as long as each sub is different.

If I can find the link to the article I read, I'll post it. It was a good article.

Also, check out the Antimode 8033 as recommended by @willemj 

I have Maggie 1.7s... started with a Rel T7 but after a year the amp in the Rel developed a problem..picked up a PSB sub and it sounded fantastic. So good in fact that it ended my love/hate relationship with my Maggie’s. PSB subs in my experience have a great synergy with Maggie’s.

I'm running Maggie 3.7i with an SVS SB16 Ultra.  It's amazing. I have a huge room, too.  I'm not an expert at subwoofer tuning, though...actually, anyone that can point me to a thread about how to tune all the options beyond just the simple cutoff frequency on the SVS SB16 would be really appreciated (phase, etc). 

Maggies are being driven by Classe CP-800 and a Parasound A21 (I have a Classe CA-2300 that is currently being repaired - see my other thread to hear about that 5 month nightmare). 

A vote here for two REL T9/i subwoofers. You can get a much better deal. Just ask a local Magnolia/Best Buy rep and they should be able to knock off up to $200 off each sub if you buy a pair. You can also contact Dedicated Audio in Arizona who offered me a great deal.

I chose the REL because of the high level speaker level input connection. I wanted to keep the setup as simple and pure (no equalizer, etc) as possible and I wanted the subs to integrate well with my speakers. By the way my speakers are Apogee Duetta Signature so there are some similarities with your Magnepans being that the Apogees are planars.

I was really hesitant putting subs in the room as I didn’t want anything to cloud the natural Apogee sound. Boy was I happy when everything was dialed in. I can listen to even less than stellar recordings now and the music just sounds great. No room mode issues and if I put something in front to hide the subs you wouldn’t even know they were there.

Try a couple T9/i subs. I think the SHO series is overkill and you may get too much boom. Either way you might have to get some corner treatments for your room to reduce boominess.

By the way I found that pulling the subs out the corners and placing them laterally on the wall with my speakers sound much better than being in the corners where they have a tendency to boom more. REL recommends to start in corners and work them diagonally outward. You have to experiment with placement and trust your ears.

By the way there is no simple answer. It’s just going with what you want to prioritize in terms of setup. I would much rather prefer a servo sub like the Rhythmic but the downside is they don’t do high level inputs. I wanted to keep the setup simple without extra equipment that to me tends to artificially contribute or take away from the sound. In following that philosophy I found the RELs to be my best bet.

You have to go with what your preferences are, and experiment to your liking.

I’m using a Sumiko S5, which is really a REL T5–as I think the companies are one in the same. 

Given my room constraints (I’m in the living room), I didn’t have many placement options. So positioning was fixed. But even so, I spent time dialing in the crossover and volume.  Let me tell you with confidence, it’s nearly impossible to pinpoint the subwoofer or tell it’s in use. As others have said, it just adds pressure to the room and opens up the whole sound spectrum. 

So so when I think of my sub, I don’t think of it as a bass augmentation device. I think and hear it as a sound spectrum device—if that makes sense. 

The only time I hear it is if I remove it from the system.  What I mean is that I hear it’s absence. 

I pair this tiny sub with PSB Imagine T2s and a tube integrated.  

@lowoverdrive --

Using the SVS SB16-Ultra myself, but have no experience with REL. From what I’ve read of the latter they’re very musical subs, and integrate extremely well with the main speakers - depending of course also on ones ability to properly setup the sub - but all things being equal, and in that regard, I’ve heard mostly positive things on the REL’s.

As has been mentioned already though I do believe SVS is the better value in all aspects of the performance arc when considering the combination of integration, musicality, extension, sheer force, radiation area, ease of setup (with their new app), etc. There was a time, I gather, when REL was the go-to brand of subs if you sought the most successfully integrated, musical sub, but with the advancements in subwoofer development and technology these latest years I’d say you can have your cake and eat it too. And by that I mean they can be both very musical and immensely powerful as well - at a fair price, that is. REL, from what I can understand, somewhat lacks the second and third part here compared to other brands, like SVS.

Do you really need more power and radiation area, at the same price, than what a REL can provide? My opinion is that you can never have too much capacity, but you can overload a room with subs dialed in too hot, be they large or small. The more capacity you have however - all things being equal - the more ease, inherent power and proper fullness you have. Perhaps REL’s still have a smidgen of a lead in overall musicality and integration, I couldn’t say, but when you consider the other traits mentioned with a sub like SVS at a similar price, my bet would be for the latter to take home the price, so to speak.

JL Audio has also been mentioned, and they appear to be excellent subs. Still, these latest SVS models like the 16-Ultras and the new 4000-series I believe you’ll get an overall similar performance envelope, though at a much more reasonable price (sometimes even by factor 2). Another brand to consider would be Funk Audio (which I would favor over JL Audio), but prices may be too steep here.

My advice would be for you to invest in a single SVS SB-4000 to begin with, try it out thoroughly within the 45 day "trial period," and if you’re convinced of its merits I’d save up some extra coins and buy a second one at a later date. Buying two to begin with however I believe you’re granted a $200 discount, but that’s $3,000 to shell out at once.

I would have bought a second SB16-Ultra had space permitted, but sadly that’s not an option as is. Still it’s wonderfully capable being the lone brute (with velvet gloves) in my setup. Here’s the Stereophile review to give you an idea of the quality level and performance scope:

https://www.stereophile.com/content/svs-sb16-ultra-powered-subwoofer

@lowoverdrive

  FYI, I don't tend to read private messages.

easier / quicker to send messages when you only have mobile access.....

@stevecham

With SVS you have a 45 day in home return for full refund.

Thanks for the info. FYI, I don't tend to read private messages.

Also, thanks for the info about room modes & issues I might face in solving related issues. I do intend to get an Antimode 8033.

With SVS you have a 45 day in home return for full refund.

I kept my pair.

True, that was also the case with my B&W PV1d subwoofer and my Quad electrostats - until I installed an Antimode 8033 Room eq unit. I honestly think that the more you do to solve the room modes issue the better.

IMO, no matter how well set-up the rooms were, there was still work to be done if you heard the RELs separately. It's all about making the entire system work with the room rather than against it.

i've heard rel paired with magnepans many times, typically in well-set up rooms, and while the rel is certainly powerful impressive, i never lost the sense that i was hearing a separate subwoofer.

With subwoofers the room interaction is far more important than the quality of the actual sub (within reason, of course). In this room the Schroeder frequency is about 150 Hz, and below that you will suffer room modes, i.e. resonant frequencies at the room’s specific dimensions. These produce pretty horrible peaks and dips in the response and are audible as boomy one note bass.
You are lucky with Magnepans as these are dipole speakers and dipoles do not excite room modes nearly as much. That also makes for a pretty big contrast with any normal subwoofer. If you have room for them, I would therefore suggest to investigate the dipole subs by Rythmik. Unfortunately they only do a kit, but there are subcontractors who will make you a cabinet (and to your taste).
Beyond that, two (or ven four) small subs will always beat a single big one with respect to smoothness. So, for a given budget, two small subs will give a smoother and more accurate response, but a single big one will be better at HT explosions. See here for an introduction: https://www.google.nl/search?q=welti+geddes+multiple+subs&ie=utf-8&oe=utf-8&client=firef...
Another interesting though bulkier option is the Swarm System by Audiokinesis, using four subs.
In every case I would add an Antimode 8033 room equalization unit for much improved bas quality at a modest price. These connect the sub at line level, however. If you only have speaker level connections you will need an attenuation cable, but that is no big deal (make sure to get a hefty one given your big power amplifier).
Both REL and SVS are respected subwoofer manufacturers. REL are nicer looking and SVS are usually better value for money (and offer a very good money back guarantee). These days REL is no longer the only one to provide for speaker level connections (though not all SVS models allow for this). In any case, if you would be using the AM 8033 this is irrelevant. In my experience REL are dead right, however, that subwoofers should only come in at the very lowest frequencies.
As for sub size vs room size, I would avoid large subs in this medium size room. For music, even two SB1000 subs will give you quite a bit of extra bass, let alone four. HT is a different story.
In my own case, I bought a B&W PV1d sub to combine with my Quad electrostats (if only for its clean and modern looks, but also for its higly adjustable dsp crossover). This only integrated properly once I added an Antimode 8033. Next on the upgrade list is a second PV1d. Not really value fo rmoney, I am afraid, but my wife likes the looks, and so do I.

@dlcockrum 's advice is spot on. 

I have a REL S5 and love it. Very powerful, as well as quick. Great for movies and 2 channel music.

Good luck! 👍