My experience adding subwoofers to 2 channel

Hello khiak,

     Well, you certainly have some excellent and expensive audio equipment in your system.  My system is a starter system in comparison to yours but I still believe my knowledge and experience with 4-sub distributed bass array (DBA) systems can be of benefit to you.
      I'm running into a few issues while determining the best bass solution given your current room and equipment.  My concern is you may be hesitant to adopt some of my suggestions because you've obviously invested a lot of money in a few of these areas and some may require room rearrangements. 
      I thought it would be best if I just described these issues in a straightforward manner with the assurance I'm not criticizing you by doing so.   My intention is just to learn more about your system's development, better understand your room requirements, get your thoughts and discuss as necessary before proceeding.  I'll assume you agree with this approach and begin describing these issues:    

1.  Why do you have so many bass traps in your room?  
     
     I fail to see the reasoning of having 4 high quality subs producing high quality bass energy in your room only to have much of this bass energy absorbed by numerous large and expensive bass traps positioned around your room.
     One of the major benefits of using a 4-sub DBA system is that it eliminates the need for all bass room treatments.  I currently use the Audio Kinesis Debra (identical to the AK Swarm but with slightly narrower subs) 4-sub DBA system in my room and the only bass room treatment I have is wall to wall carpeting.  Do you have hard surface or carpeted floors in your room?
    The above is the description of the 1st issue I wanted to address with you.  My initial suggestion is to remove all of the bass traps currently in your room.  They're not only not necessary, this would also free up a lot of floor space for optimum positioning of your 4 subs.
     I know these bass traps are expensive but I really don't think they're doing anything to improve the perceived bass response in your room, although I'm sure an ASC sales rep would disagree.  Are you okay with removing all your bass traps?
     It sounds like your 21.0LX subs are on the left wall in front of your equipment deck and near your left Kharma main speaker. Both of them?  Are they currently hooked up and running or just stored there for now?

2.  My current thinking is you place both 21.0LX subs on the front wall, replacing your JL subs.  Set each sub's delay and phase setting to zero  and adjust the volume and xover frequency identically for both until the bass sounds the best to you at your listening seat. 
     Then place a JL sub on each left and right wall, about 1-3 feet away from the rear corners and, with both front subs running, set each sub's room control to "off" and phase setting to zero and adjust the volume and xover frequency identically for both until the bass sounds best to you at your listening seat. 
     Of course, having an assistant make the adjustments as you evaluate the sound will be very helpful.  Once the bass sounds very good to you at your listening seat, adjust the phase control on each sub, in sequence one at a time, to check if altering the phase on any single sub improves the overall bass even further. If not, just leave them all set to zero which is in-phase.       
     A 2nd option could be using what  M-db also mentioned about JL Audio currently marketing a version 2 room processing and a separate CR-1 Crossover component which could be useful just in case the above configuration and sub positioning doesn't provide excellent bass response performance in your room.  I'm going to check this out and see if it'd be useful for your scenario.
     A 3rd option could be the method I used for positioning each sub, which involves a sequential positioning I can explain later if needed.
     Please let me know your thoughts, comments and questions.

Tim

Hello Tim,
In 2000, I bought a pair of MBL101D Radialstrahier speakers. I enjoy listening to my music very loud around 85dB to 90dB, so you can imagine in a room 18’X12’X9’ without acoustic treatment, everything sound bad especially the bass. So I got ASC Mr Art Noxon from Seattle to design the acoustic for the room.

The floor is concrete overlay with 3” wide 0.75” thick 48” Long teakwood of various length

Hello Tim, 
Is there a way I can send you a video clip of the room? 

Tim, sorry I did not get back earlier. I can not believe people are so far off on the subject of time and phase. Time and phase are intimately related. wire two of your subs backwards and see what you get. That is 180 degrees out of phase. You get exactly the same effect when the distance between speakers is different. The wave length of a 100 Hz tone is about 10 feet. If you put one sub 5 feet closer to you than another you get exactly the same effect as if you wired one speaker backwards. Music is not one tone so you get every frequency altered by a different phase angle. Then you have a range of frequencies to deal with at the cross over which depending on slope may be as high as 250 Hz. It is also not only about what you hear but about what you feel. In phase you feel the thud of that bass drum strike. Out of phase and you feel nothing. You can easily demonstrate this to yourself by reversing wires. A system that is aligned in phase and time is a wonderful thing to hear and feel. It is much more realistic. If I blind folded you, drove you around and brought you into the room you would think you were in a jazz bar. I'm afraid millercarbon is spouting off with excuses to support his infatuation with SWARM systems, all of which are entirely unsupported assumptions which in reality are entirely wrong. Humans are marvelous creatures. When they don't know what is going on they make stuff up. They mythologize. Zeus, great explanation for lightening don't you think?

Oh, and Tim. I am not saying that in certain situations a DBA system may not be the easiest way to reasonable bass performance. It may work reasonable well for many people. What I am saying is that in the end it will not produce the most accurate and realistic results but do to do so usually requires advanced digital speaker control that at this time costs at least $6K. If however you have a tape measure, some savvy and some luck, you might be able to get there without the computer. An important part of this hobby is being able to screw around with your system to see if you can get it to sound better and in doing so you learn. So, start screwing around!