My experience adding subwoofers to 2 channel

Hello Tim,
Many thanks for your kind offer to help me in the setup of the 4 subs in my music room. 😃😃😃

After viewing Audiogon forum on getting better bass performance with 4 subwoofers in a room, I decided to give it a try. So I added two 21.0LX to my existing two F212.v1 early this month. Instead of adding another two F212v2, I decided to go for 21 inches woofers as I have never heard the bass from such woofers in my life. I have owned the F212v1 for 6 years but I have to say the bass of 21.0LX is awesome.

I have a fix Stewart movie screen frame 94” X 55” at the front wall about 5 ft behind the tweeter of main speakers. The bottom edge of the screen frame is 27” from the floor. From the left edge of the screen frame to the left wall, there is a ASC full round tube trap from floor to ceiling, similarly on the right edge. From the bottom of the screen frame to the floor, I have half round ASC tube trap horizontally. I have 2 half round ASC tube trap mounted on the ceiling between the 2 corners full round tube trap. There is a set of 3 half round tube traps mounted on the ceiling across the width of the room above the main speakers.
A Revel voice 2 center speaker with mounting pedestal sit in front of the movie screen with the F212v1 at each side. The subs are about 2 ft from the edge of the Center speaker.
The Kharma Exquisite Reference 1E Signature main speakers are 7ft apart and the F212v1 is about 1.5ft behind the main speakers inner side. Between the main speakers are 3 rows of 5 mono amps and preamp power supply. Left row is Goldmund Telos 600 stack on top of each other for left main speaker bi-amps, middle row is Goldmund Telos 600 mounted on the bottom of 2 deck rack for the center speaker. The power supply of the Goldmund Mimesis 22S sit on the top deck of the rack, right most row is Goldmund Telos 600 stack on top of each other for the right main speaker bi-amp.
The Goldmund Mimesis 22S Signature preamp sit on a rack in front of the Rack for the center  speaker power amp. 
On the right wall 1.5 ft away from the right main speaker are 3 rows of 3 deck racks where two Mark Levinson N332 for Revel Embrace surround and Vienna acoustics back speakers, Marantz MM8077 for  four Beale Street ICA6-BB height speakers and two Bose wide speakers. Marantz AV8802A processor, Pioneer DVL-919, Dream Vision Sealer 3, Lexicon RT-10, Phillips BDP9600 and Panasonic DMP-UB900 are located.
On the left wall 1.9 ft from left main speaker, sit the 21.0LX follow by a rack with 2 deck for the Reimyo CDP-777 and DAP-999EX and finally the door to the room.
On the corners of the back wall are full round ASC tube traps from floor to ceiling with a 70”X16” wall mounted Blueray cabinets on their side and 3 columns floor to ceiling full round ASC tube traps between them.
The right and left walls above the rack height are space with ASC sound planks. At the wall just beside the main speakers are custom wall mounted reflective towers.
The main listening chair is 7ft from the main speaker and 12ft from the front wall.
The JVC RS-65U projector is mounted to the ceiling directly above the main listening chair.
Hope all these info are helpful. I wish I can send you photos which are much better.

😃 Thanks 
khiak

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?