Better Subwoofer for 2 channel Music: Focal Utopia Sub or JL Fathom f113


Hello Everyone,

I am looking for a good sub at about the 2K price point and am considering either the Focal Utopia Sub (15" woofer, 1000W RMS) or the JL Fathom f113 V1 (13.5" woofer 2500 RMS)- The fathom being slightly more expensive on the ’used’ market.  Both subs are highly rated and the Fathom seams to be very highly regarded on this site so I would like to try it. At the same time, my speakers are FOCAL Utopia BE series so I think the Utopia Sub will gel nicely and I would be able to save several hundred bucks to put towards other tweaks if I went with the focal sub. Currently I have a Monitor Audio Gold 12 Sub (12" woofer 600W RMS) which is very good, but want to see if either the Utopia or the Fathom is much better,  and I mostly use the Monitor Audio in my HT set up anyway.

Specs wise:

Focal Utopia BE Sub  - 15" woofer, 1000W RMS

JL Fathom f113 V1  - 13.5" woofer 2500W RMS

Both subs go down to ridiculously low Hz.

Usually, I am less into specs and more about hearing music (and not sure how important these specs are anyway) but I am not able to audition either of the subs (let alone in my system) , so kinda shooting in the dark and would appreciate some advise on which way to go as these are also heavy and expensive to move around to deal with!.

I imagine I will keep the new sub for a while.

I’d like the sub to merge with my speakers as seamless as possible, and provide that extra lower-level feeling and punch when needed.

Does anyone have experience with either (or both to compare)? Thank you in advance.


Aside -   My 1 pair of preamp LXR-outs is taken up by the connection to the Amp. So I would connect the sub via one of the two remaining RCA outs from my preamp - is there is a better way?

Ag insider logo xs@2xjmarshak

Hello jmarshak,

      The truth is that a single sub, no matter the quality, size or price, is not going to perform as well as two good quality subs in any given system and room.  You'll achieve better in-room bass response using two good quality smaller subs.  The bass will sound smoother, more detailed and more dynamic because there are two subs sharing the bass duties and not just a single sub being required to produce it all and possibly being overdriven and stressed.   I'd suggest you consider using two of these will provide better bass response and integrate more smoothly with your main speakers:
www.svsound.com/products/sb-1000?variant=9532234051&gclid=Cj0KCQjwgLLoBRDyARIsACRAZe7Yb0D_Yzqu6P...
 

     For even smoother, more detailed and more dynamic bass response, arranging three of these in a distributed bass array (DBA) system would provide outstanding bass response.  The DBA concept is a proven method developed by acoustical experts, Dr. Earl Geddes and Floyd Toole, to achieve near state of the art bass response in virtually any room and integrate seamlessly with virtually any pair of main speakers, even fast planar-dynamic and electrostatic speakers.
     I use a 4-sub DBA system in my room with outstanding results. I use the Audio Kinesis Swarm system that consists of 4 relatively small passive subs (unamplified 1'widex1'deepx24"tall subs with a 10" aluminum long-throw driver in each) powered by an included 1,000 watt class AB amp/control unit that sells for $2,800.  Here's an Absolute Sound review of the Swarm system for more details:

www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/


Tim

Hi jamarshak,

I've had subs for years and can share my experiences and 'growth' as it may be;  For many years I have had several M&K subs,  They were the sh## in their day, dual 12" push pull, very articulate but not the absolute 'deepest'.  But what I quickly learned, was that two stereo subs, each being fed by distinct left and right inputs if possible, was way better than one sub, no matter how great it is.  +1 to noble100 on that.  (and I am sure that 4 in an array is the best but that is not going to happen for me).  Anyone that says you can not localize where a sub is is just wrong or can't hear.  I can sit right in the center with one sub blindfolded with mittens and tell you where the sub is, even when adjusted well.  So two is the bomb.  About two years ago I got a paradigm studio 15 new on a  great clearance.  Wow.  Deep and low.  but just one...(the M&K's are now gone).  So I got another and had stereo 15' paradigm's, pretty nice.  
But the lady thought they were hideous, and I was able to use them downstairs, so I started researching Rel.  Now I feel I have grown up about bass and subwoofers.  I now have stereo REL Carbon Limited's.
It is not about just hearing and feeling the deep stuff, but it about how they pressurize the room and support the stereo imaging and sound of my Revel Studio 2's.   I have a large room, all open from family through eat in area to kitchen.  So  a lot of air.  The sub's you ask about are also awesome, but it is about how the REL's feed their input off of the amplifier to receive the 'exact same timing etc' to keep everything sweet.
I also use the Longbow wireless and it works easily and perfectly.
And get this, the lady thinks these REL subs look good!  Read everything on the REL site before you purchase anything.  The Rel SHO 5's would have worked but what the hell...and you can find discounts on new REL subs.
Hello fastfreight,

    We all are unable to localize deep bass frequency soundwaves, that is determine where the sound is coming from, that are below about 100 Hz but we're very good at localizing higher frequency soundwaves in the remainder of the audible spectrum, from about 100 to 20,000 Hz.
    This is the reason there's no such thing as 'true stereo' deep bass and why the bass is summed to mono on frequencies below 100 Hz on all vinyl and cd recordings. If you doubt this, try to find a single vinyl or cd recording that is not summed to mono. This means it's pointless to configure subs in a stereo configuration with one located by the left main speaker and one by the right.
    However, thanks to psychoacoustics and our remarkable brains, it is possible to create the perception of stereo bass in our systems. Here's how it works:
    Whether you use  2, 3 or 4 subs, run them in mono and optimize the bass at your listening seat.  The bass below 100 Hz won't be able to be localized but there are bass harmonics or overtones of the deep bass fundamental frequency that extend into higher frequencies that are reproduced by the main stereo speakers and can be localized.  Our brains are able to associate the fundamental deep bass frequency reproduced by the subs, that are not able to be localized, with the deep bass's higher harmonic frequencies, that extend well beyond 100 Hz, which are reproduced by the main speakers that are able to be localized.  This psychoacoustic association allows us to localize the deep bass in the soundstage, for example the kick drum is located in the rear center and the upright bass is located in the front to the left, which would not be otherwise possible without this psychoacoustic association our brain's are capable of.  
     Other factors I think are important to integrating subs seamlessly with the main speakers are the subs volume levels and the crossover frequency setting.  I'll try to discuss my opinions on these factors in a future post.


Tim
All good info in posts with which I generally agree. To the OP who asks about specific subs, Focal, JL, I’ll say this:
I know nothing about the Focal but enough about JL to be dangerous. Using a JL in my system F112 v2 has really upped my game, one of the most valuable upgrades I’ve made. That said JL has had their share of issues that were addressed in their v2 versions. I’d stay away from earlier versions. The JL IMO is the current leader in subwoofers. Very well defined, articulate, tight, fast, accurate and reproduces the lows down to below your hearing, below hearing you can feel it though.It has all the functions available to integrate it with your system regardless of name brand and will integrate seamlessly with some effort. Once I properly integrated my sub it gave a truly magical representation of the material. It’s a powerful piece of audio equipment. It also has its own room correction software to tame the modes. I do not use the correction as my listening space is such that it’s not necessary. Depending on material localization can be easily determined at frequencies mentioned in other posts depending on your crossover settings. Would I like a dual setup? Absolutely but at the price I easily can live with just one.

Add in to address hook up question, 
I have my sub connected to the Preamp via its available variable RCA output. This allows for the Preamps volume control to adjust sub volume simultaneously with the left and right channels. 

My space dimensions are 15 x 23 x8
Hope this helps,

Read this prior thread first

https://forum.audiogon.com/discussions/what-are-considered-to-be-the-best-subwoofers-for-2-channel-m...

A repost and good summation of the conflicting strengths and warts in setting one up properly and more importantly , first considerations  you would undertake to do so. 

http://ultrafi.com/why-everybody-needs-a-good-subwoofer/


August 3, 2008 by ultrafi in Tips, Tricks & Info | Comments Off on Why Everybody Needs a Good Subwoofer…

" …And Why a Really Good Subwoofer is so Hard to Find

Audiophiles and music lovers are missing out on one of the most dramatic improvements they can make to their audio system: Powered Subwoofers. Most audiophiles won’t even use the word “subwoofer” in public, let alone plug one in to their precious systems. There is a kind of snobbery that exists in the world of high-end audio aimed primarily at receivers, car audio, home theater and especially subwoofers. As a matter of fact, subwoofers are responsible for many people disliking both car audio and home theater, since it is the subwoofer in both of those situations that tends to call attention to the system and cause many of the problems.

The truth of the matter is that subwoofers have fully earned their bad reputation. They usually suck. Most of them sound boomy, muddy and out of control with an obnoxious bass overhang that lingers so long as to blur most of the musical information up until the next bass note is struck. We have all had our fair share of bad subwoofer experiences, whether it’s from a nearby car thumping so loud that it appears to be bouncing up off the road, or a home theater with such overblown bass that it causes you to feel nauseous half-way through the movie. You would think that high-end audio manufacturers would be above all of that, but you would be wrong. In many cases, their subwoofers are almost as bad as the mass-market models because they too, are trying to capitalize on the home theater trend that is sweeping the land.

You see, it’s very difficult and expensive to build a good subwoofer. One reason is that a sub has to move a tremendous amount of air, which places big demands on the driver (or drivers). Moving lots of air requires a lot of power and that means an amp with a huge power supply, which can cost huge money. Finally, in trying to move all of this air, the driver (or drivers) which operate in an enclosure, create tremendous pressure inside of the box itself. The cabinet walls must be able to handle this pressure without flexing or resonating. Building such a box involves heavy damping and bracing which gets very expensive. When you consider these requirements, you quickly realize that it is virtually impossible to build a really good subwoofer (I mean good enough for a high-end music system) for under $1000. Yet most of the subwoofers out there sell for between $500 and $900. Manufacturers do this because their marketing research has shown them that that is what people want to spend on a sub, never mind the fact that what people want to spend and what it takes to get the job done right may be two different things. The result is that even most high-end manufacturers are putting out poorly constructed subwoofers that just don’t sound very good.

I don’t want to give you the impression that anyone who really wants to can build a good subwoofer so long as they are willing to throw enough money at the problem, because that really isn’t true either. There are some pretty expensive and well-constructed subwoofers out there that you would never want to plug into your music system because they would most certainly make the sound worse. Why? Because of their crossovers. A crossover is inserted into your signal path in order to remove the lowest frequencies (the deep bass) from your main speakers so that they no longer have to do all of the dirty work. The deep bass will instead be dealt with by the subwoofer. The #1 benefit of adding a high quality subwooferto your system is not how it further extends the bass response, but how it can dramatically improve the sound of your existing power amp and main speakers from the midrange on up. That, my friends, is by far the most compelling reason to add a sub to your high-end music system. Once your main speakers are freed from the burden of making deep bass, they will sound cleaner, faster and clearer, especially in the midrange and midbass. They will also image way better because there will be far less air pressure and therefore resonance and vibration affecting their cabinet walls. And since the power required to make the deep bass is provided by the subwoofer’s built-in amplifier, your main power amp will be free from that burden and begin to sound like a much more powerful amplifier. The one big problem with all of this is that you need a crossover to roll off the deep bass in your system and achieve all of these benefits. And the crossover that comes with almost every subwoofer on the market will cause more damage to your signal than can be overcome by these benefits. That is the main reason that audiophiles refuse to consider adding subwoofers, even very expensive ones with well built cabinets.

Enter the Vandersteen 2Wq 300 watt powered subwoofer. This is the only subwoofer that is specifically designed to be inserted into the highest of high-end music systems without doing any harm to the precious signal. So how does Vandersteen do it? Simply. In fact his crossover scheme is so ingeniously simple that it’s a wonder nobody else thought of doing it the same way. I’ll spare you an in-depth description and just say that the only thing you end up inserting into your system is a couple of high quality capacitors. That’s it, nothing more! No additional wires or gadgets enter your signal path. Hell, you don’t even have to disconnect the wire between your amp and speakers to add this subwoofer. The model 2Wq sub uses the same basic crossover scheme as the $15,000 flagship Model 5As. As a matter of fact, you can even run the specially designed Model 5A crossovers (M5-HP) with the 2Wq if you want the most transparent sound imaginable.

So what about the other reason to add a subwoofer to your system: for more powerful and extended bass? I don’t care how big your main speakers are, they’re no match for a good subwoofer in the bass. A really good subwoofer can run rings around the best floorstanding speakers when it comes to bass extension, power and control because it is designed to be good at that and nothing but that, whereas main speakers have to be good at higher frequencies as well. Ideally, you want two subwoofers so that you have true stereo separation down deep into the bass. Stereo subs can also help to lessen room interaction problems by providing two discrete sources of bass information. Remember, if you can’t afford to buy two subwoofers at once, you can always add the second one later. Adding a pair of 300 watt powered subwoofers is exactly like adding a pair of 300 watt monoblock amplifiers to your system and upgrading to a pair of better main speakers at the same time. The beauty is that you don’t have to replace your main power amp or speakers to do it.

But there is a problem here as well. Everything comes at a price, and the price you pay with most subwoofers is that when you add them and their built-in amplifiers to your system, they don’t tend to blend or integrate well with the sound of your power amp and speakers. This is especially true if you own a tube amp, because the character of your amp is nothing like the character of the big solid-state amp that is built into most subwoofers. The result is that your system sounds split in half. You can hear where one part of the system leaves off (namely your amp and speakers) and where the other part takes over (the sub and its amp). This is a HUGE problem for audiophiles who aren’t willing to destroy their system’s coherence for additional power and bass extension. Fortunately, Vandersteen has the perfect solution for this problem that is, again, so simple, I wonder why nobody else thought of it first. His solution is to build a very powerful 300 watt amplifier that strictly provides the huge current needed to drive the subwoofer. You can think of this amplifier as only half of an amplifier; or just the power portion of an amplifier. The release of this power is controlled by the signal that is provided by your power amp. Vandersteen’s amplifier needs a voltage to modulate its current output, and what better place to get that voltage than from your main power amp? This way, your power amplifier is directly responsible for the sonic character of the deep bass coming from the subwoofer because it provides the necessary voltage signal. This voltage signal contains the unique and characteristic sound of your main power amplifier and insures that that character is maintained in the sound of the subwoofer itself. The beauty of it is that your amplifier is only providing a voltage reference and no actual current, so it is not taxed with the burden of “driving” the subwoofer in any way. As a matter of fact, your amplifier doesn’t even know that the sub is connected to it. The 2Wq’s potential is almost unlimited given that it will ratchet up its performance as you improve your power amp. Remember that you always want your subwoofer to sound just like your power amp. No better, no worse. NO DIFFERENT!

After having spent time with the amazing Vandersteen Model 5A loudspeakers with their 400-watt powered, metal cone subwoofers, we were reminded of the sound we had with the awesome Audio Research Reference 600 mono power amps. With the Ref 600s there was a sense of effortlessness, openness and unrestricted dynamic freedom that we have only otherwise heard with live unamplified music. Listening to those monstrously powerful amps made us realize that all other systems sound compressed by comparison. Only when we heard the new Vandersteen Model 5As with their hugely powerful built-in subwoofers, did we again have a strikingly similar sonic experience. The reason is that the Model 5As provide a total of 800 high-quality watts, to which you have to remember to add the power of the amp we were using, the ARC VT-100, at 200 watts. This means we were listening to about 1000 total watts of amplifier power – not far from the 1200 total watts provided by the Ref 600s. With the Vandersteen subwoofer crossover and amplifier, you are able to get those hundreds of subwoofer watts to blend seamlessly and even take on the character of the ARC VT-100. It’s amazing! What’s even better is that the price of the system with the Model 5As and the VT-100 is under half the cost of the Ref 600s alone! Since this discovery, we have achieved the same kind of unbelievable dynamics and seamless blending with ProAc loudspeakers and twin Vandersteen 2Wq 300 watt powered subs. So, if you want the sound of Ref 600s but cannot afford them, buy a pair of Model 5As or your favorite pair of ProAcs plus a couple of 2Wq subwoofers and mate them with a VT100 and you’ll get surprisingly close. You can cut the cost even further by running a pair of Vandersteen 2Wq 300-watt subwoofers with your existing speakers. Or mate a pair of 2Wqs with your favorite ProAc. In any case, it is the magic of SUBWOOFERS that allows this to happen. It is for all of the above reasons that there is only one subwoofer in existence capable of integrating seamlessly into a high-end music system, allowing you to reap all of the benefits of having a subwoofer, with none of the drawbacks. And the Vandersteen 2Wq is the one. And just in case you think I am a biased source, our correspondent Blaine Peck (who, for all you know is also a biased source) recently wrote the following, with no discussion between us about the topic prior to his sending us his comments. Whether reproducing the plucked string of an acoustic bass or the sound of an analog synthesizer, the Vandersteen 2Wq subwoofer is a seamless extension of any system. Nothing else need be added! With its internal 300-watt power amplifier, it is the perfect compliment to any sound system. Designed to take on the characteristics of your main stereo amplifier, the amp in the 2Wq will not sound foreign in your system. Also, through an extension of the Vandersteen design philosophy, a unique gradually sloping crossover system is implemented so you simply do not know where your main speakers stop and the 2Wq begins.

Now that your main speaker/amplifier combination need not concern themselves with those power demanding low frequencies, they are freed up to work in a more comfortable range. Yes, now what is coming from your main speakers will sound better than ever.

The 2Wq is not just another subwoofer. It consists of three 8″ floor-facing drivers, each with a massive motor. So why not a more typical single 12″ or 15″ design? Well frankly, the mass of a larger driver will not allow it to respond as quickly as the Vandersteen 8″ drivers to today’s demanding recordings. The 2Wq’s 8″ drivers are designed to handle the content but be “fleet of foot” at the same time. Concerned about where to put them? You need not worry. With the control of both its respective level and the “q” (how loose or tight the low end is) you have the flexibility to place them in a location that fits your living environment and not sacrifice performance. The simple beauty of this product will soon become an addition to your room.

So whether on orchestral music, hard rock or something in between, the Vandersteen 2Wq will exceed your expectations...."
Um, no. It's actually quite easy to build a good sub. The problem is always integration with the other speakers and the room.

If you don't have room correction already, buy the sub with the best options built in. 

If you can't get that, buy the smallest sub you can.

Best,

E
@akg_ca , what a great synopsis of the subwoofer and quite truthful in many ways.............................all the way to the blatent plug or advertising for Vandersteen, I stopped reading at that point.
Are Vandersteen good? Probably. Are they the absolute best? I doubt it. .Are they the only sub in the marketplace of audiophile subwoofers that will satisfy the discerning audiophile? I'll leave that answer to the discerning audiophile. Subwoofers are one of those animals where you get what you pay for at least for now. I don't know what your Vandersteen cost but am pretty darn sure there are equally capable  products from other manufacturers.
These are all great response. thank you. 

I surmised a couple of things..

1) To perhaps focus on REL or JL but its a bit harder for me to get ahold of a REL
2)The RCA hookups from preamp is fine.
3) That perhaps two smaller 'good quality' subs may be better for 2 channel music than one larger one.  (i.e two f112s better than a single f113).  I just don't think that going to a three or four sub configuration is practical for me.  I might just get one sub and see how it works by itself and with my Monitor Audio.  

One person mentioned to stay away from the JL Version 1.  Does anyone have  a good account of exactly what JL upgraded in the V2s? 

My room is like 20'x20'x8'.  Two couches, carpet.  Should I be concerned that a single f113 may be two 'large' or overwhelming or can it always be dialed down?
@gillatgh,
Though Akg's post might sound like a plug for Vandersteen, the post does show how such a simple way to incorporate a sub not only makes sense, but works.
Yes, there are other subs out there, but few are built to last like the Vandersteen's. My 2w's were probably over 20 years old, yet still functioned as they should. I would ask the OP to look up previous threads regarding JL subs and the parts they use.
I also own a pair of HSU subs. They are quite good for the money, but took a long time to get integrated properly- Unlike my Vandy's which only required adjusting the impedance on the crossover.
@jmarshak , 
I would also consider the Audiokinesis Swarm. I haven't heard it, but people I consider knowledgeable on the subject, swear by them. 
Bob
The issue with sub size is integration.

Smaller subs are just less problematic than larger subs. The higher cut off prevents you from waking the dragons that live in the depths. Less chance of exciting nasty room modes, therefore, they sound better if you don't have adequate EQ and room treatment.

However ... given good EQ, treatment, and exact calibration, larger subs can be breathtaking.
.“....@akg_ca , what a great synopsis of the subwoofer and quite truthful in many ways.............................all the way to the blatent plug or advertising for Vandersteen, I stopped reading at that point.
Are Vandersteen good? Probably. Are they the absolute best? I doubt it. .Are they the only sub in the marketplace of audiophile subwoofers that will satisfy the discerning audiophile? I’ll leave that answer to the discerning audiophile. Subwoofers are one of those animals where you get what you pay for at least for now. I don’t know what your Vandersteen cost but am pretty darn sure there are equally capable products from other manufacturers....”

@gillatgh

I’m not pushing Vandersteen subs as the “best”.... there is no one “best” in my opinion. This was the full audio reporter article, and his comments on a specific brand fave may or may be noteworthy to a reader, but they are his editorial comments alone.

i totally agree that there are many other brand equals and superior choices as long as one remembers that everything is entirely bespoke/ unique system dependent...,, full stop.

my takeaway from that article is simply twofold as highlighted in his article:

$$ alone as a decision criteria is a pathway to a failed experiment, He has a valid comment that general audio mass market buyer has sticker shock at a under $1000 level,and its nigh on impossible to get a quality performer at that modest level. ANd similarly, simply throwing a large $$ at a sub is a pure gamble at best with a a high likelihood on system incongruity and poor integration regardless of price,

his best takeaway is that BOTH the design and the build of the crossovers are key...

Have I personally auditioned VANDY subs? Yes.
are they good? Yes.... VERY GOOD.and a contender and no pretender .
are they different with a very fast sonic signature ? Yes
Do I think it’s the only Yellow Brick Road to my audio OZ? NO... ,I still have a CASTLE CLASSIC sub ( a quality build and good performer built by ATC) for now.

There is no “Best” ...this crazy hobby choice of auditioning contenders and pretenders is a bespoke journey and NEVER a destination
akg_ca:
"Ideally, you want two subwoofers so that you have true stereo separation down deep into the bass. Stereo subs can also help to lessen room interaction problems by providing two discrete sources of bass information."

Hello akg_ca,
   Your statement cited above is not accurate.  Two subs will not and cannot provide true stereo separation down deep into the bass. The information below, however, is accurate and useful to know:
   
     Virtually all humans are unable to localize deep bass frequency soundwaves that are below about 100 Hz.  This means we cannot determine where the sound of bass tones are coming from that are below about 100 Hz.  But we're very good at localizing higher frequency soundwaves in the remainder of the audible spectrum, from about 100 to 20,000 Hz.
      This is the reason there's no such thing as 'true stereo' deep bass and why the bass is summed to mono on frequencies below 100 Hz on all vinyl and cd recordings. If you doubt this, try to find a single vinyl lp record or cd on which the bass is not summed to mono and has discrete L+R bass content recorded. This means it's pointless to configure subs in a stereo configuration with one located by the left main speaker and one by the right.  A better approach is to simply operate all subs in mono mode. 
      However, thanks to psychoacoustics and our remarkable brains, it is possible to create the perception of stereo bass in our systems. Here's how it works:
     Whether you use 2, 3 or 4 subs, run them in mono and optimize the bass at your listening seat. The bass below 100 Hz won't be able to be localized but there are bass harmonics or overtones of the deep bass fundamental frequency that extend into higher frequencies that are reproduced by the main stereo speakers and can be localized. Our brains are able to associate the fundamental deep bass frequency reproduced by the subs, that are not able to be localized, with the deep bass's higher harmonic frequencies, that extend well beyond 100 Hz, which are reproduced by the main speakers that are able to be localized. This psychoacoustic association allows us to localize the deep bass in the soundstage, for example the kick drum is located in the rear center and the upright bass is located in the front to the left, which would not be otherwise possible without this psychoacoustic association our brain's are capable of.  
     Other factors I think are important to integrating subs seamlessly with the main speakers are the subs volume levels and the crossover frequency setting.  For best results, the precise level of these settings will vary by system, the main speakers and the subs used.     
     My main speakers are a pair of 6'x2' Magnepan 2.7QR 3-way planar-magnetic dipoles that are very detailed and smooth but have limited bass extension (down to only 35 Hz) and limited bass impact and dynamics.  To provide the missing bass extension and impact, I use an Audio Kinesis  4-sub Debra  distributed bass array (DBA) system that is very similar to their Swarm system, consisting of four relatively small passive subs with 10" aluminum long-throw drivers powered by a separate class AB 1K watt amp/control unit. 
     My goal was to keep the perception of the four dynamic subs as low as possible, have them only become active when the source material required it and to blend in with my main speakers as seamlessly as possible to attain a cohesive unity to the overall sound quality.  I've achieved the best performance and integration results thus far by running my mains full-range with the subs' volume level set at about 45% and a cutoff frequency of 40Hz.  I believe using multiple subs with smaller and quicker 10" drivers, rather than larger but slower12-15" drivers, allowed the bass to better match the accurate, agile, detailed and smooth sound qualities that the Magnepan main speakers possess, resulting in a seamless blending or integration between the subs and mains.
     I agree that many systems will achieve significant improvements in overall sound quality by utilizing the high frequency pass thru connections for the L+R main speakers on most subs and the Swarm/Debra's amp/ control unit.  This is because the main speakers and their amps are relieved of the need to reproduce deep bass frequencies (usually with a cutoff of about 80 Hz) which usually results in improved midrange and treble performance from the main speakers and amps combination.  I tried this method but didn't notice significant improvements in the midrange and treble performance of my Magnepans and D-Sonic mono-block amps combination.  My thought is that, since these class D mono-blocks are capable of outputting 1,200 watts into my 4 ohm main speakers, the relief on the power requirements gained from the amps and speakers not being operated full-range didn't result in the normally significant sound improvements in mid-range and treble response attainable with less powerful amps and different main speakers.
     However, I realize every system is unique and suggest trying out both configurations, running the mains full-range and with restricted low frequency output, to determine which you like best.
   
 



Tim  
Thank you all for your help  Ill try a JL.
Best Regards