Eminent Technology LFT 7 !!

     How about using your LFT 6 and using a high quality 4-sub distributed bass array (DBA) system like the Audio Kinesis Swarm reviewed below?

https://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/
     
     If you have the space to position these 4 relatively small, 12"Wx14.5"Dx28"H, subs with 10" aluminum long-throw woofers asymmetrically around and facing your room perimeter walls, I'm fairly certain this high qualitybass system would be an excellent solution paired with your high quality Eminent Technology LFT 6 main speakers. 
     I've used this bass system for about 5 years now, initially with a pair of Magnepan 2.7QR main speakers and currently with a pair of 3.7i for both music and with Oppo 105 and 205 Bluray universal disc players on 5.1 surround systems for HT.
     The 4-sub  DBA concept was first discovered through scientific research and experimentation somewhat simultaneously by acoustic experts such as Dr. Earl Geddes and Dr. Floyd Toole and then further developed by audio industry members such as Todd Welti of Harmon International and Duke Lejeune of Audio Kinesis. 
     This bass system concept implementation results in bass performance that is near state of the art in virtually any room and with any pair of main speakers, even those generally considered too fast and detailed to integrate well with conventional dynamic cone subs such as planar-magnetic and electrostatic panel type main speakers.  With 4 subs operating in concert, the bass extends down to 20 Hz +/- 3 dB, is as powerful and dynamic as the source content dictates, is very smooth, fast, detailed, with a sense of ease quality that is very natural on all genres of music and integrates seamlessly with any pair of main speakers. 
     You might reasonably think I'm exaggerating but I really don't think that's possible given the extremely high quality bass this 4-sub DBA system reproduces in my room and I believe will also reproduce in your system and room.  It's fairly expensive at about $3K, which I rationalized as about the same price as 2 high quality subs, but it's also a complete kit that contains everything you need except the speaker cables (4 subs, 1,000 watt class AB amp with volume, cutoff frequency, limited equalizer and continuously variable phase controls.  Each sub comes with conical spike footers and a port plug for operating in your choice of ported or sealed mode.  I believe AK still offers a 28 day free in-home trial period that takes almost all the risk out of an audition, too. 
     I found the attached Absolute Sound review of the AK Swarm above to be very accurate and will give you a good description of what to expect in your system and room.  I consider this the last sub system I'll ever need because I'm certain it will perform very well even if I move or change main speakers.
     You can check out my system pics on my profile if you're curious about how they look and are positioned.  The current pics are my former system with the 2.7QRs.  I'll be posting updated pics in the next few days with the 3.7is, $3K in new GIK room treatments, a new OLED 4K hdtv and a few other new components.

Best wishes,
    Tim

Yes I believe in the Swarm bass array.  I currently own all components, cabinets made, for 4 Dual driver GR Research Servo Subs modeled after the GT Audio Works system.  So assembly will begin shortly.  My main listening room is 22x53x10 and is being remodeled.  I decided to go this way only because I have always wanted to experiment with servo controlled bass drivers and the cost to do so has become realitively reasonable.   I am not tied to OB/Dipole for bass but it is possible.  The PAP Quintet 15 proves that.  The Linkwitz Lab lx521.4 proves that.  For sub bass closed box is best to my ears.  Tastes varies.

Hello riverdinaudio,

      I have listened to numerous high quality subs including dipoles but have never listened to OB or any GR Research subs.  My only experience utilizing 4 subs in a distributed bass array (DBA) configuration is the Audio Kinesis Debra 4-sub complete DBA kit system I bought and installed about 5 years ago in my 21'x15'x8' room.  This system is identical in price, sub amp/controller utilized and concept to the AK Swarm system except the Debra subs are more rectangular at 12"Wx14.5"Dx28"H.  
     I initially used Magnepan 2.7QR 3-way 6'x2' dipole panels as main speakers with no room treatments, DSP room correction or EQ and ran them full range (35-20K Hz) with all 4 Debra subs operated in mono, without the port plugs and a 40Hz cutoff frequency setting, so all 4 subs in mono and  ported configuration operating between 20 and 40 Hz.
     This setup provided what I consider near sota bass performance in my room that was fast, smooth and detailed enough to seamlessly integrate with the 2.7QRs while still providing the powerful deep bass impact and dynamics I felt they lacked.
     A couple months ago I upgraded to a pair of Magnepan 3.7i main speakers, which are the same size and 3-ways but have the true-ribbon treble transducer instead of a quasi-ribbon transducer, and fully treated my room with $3,500 worth of custom installed GIK room treatments.  You can view my recently updated system pics to view the results.
     Long story short, the true-ribbon treble section and other 25 year newer technology of the 3.7i main speakers, along with the room treatments, significantly improved the overall detail, sound stage imaging, naturalness, quality, realism and overall enjoyment of my system. And I  perceive the sota bass performance and seamless integration with the new 3.7i main speakers provided by the 4-sub DBA system as even more  impressive, which I didn't think was possible.
     So in summary, I'm stating that I'm thoroughly convinced of the 4-sub DBA concept's effectiveness in my room and believe you'll be thoroughly convinced if you deploy one in your room.  However, I'm not stating that 4 high quality GR Research/Rhythmik OB or servo-controlled sealed subs wouldn't perform and sound equally as well or better in a DBA confguration, because I've never heard them and just don't know.

Best wishes,
    Tim