My experience adding subwoofers to 2 channel

Hello Tim,
 “ I just sent you a personal message. You should see a 'dialogue bubble' icon on the upper-right side of your screen, next to the 'shopping cart' icon. Just click on that and my pm should show. Click on my pm and I think you can hit reply and attach your video clip before sending.
 I'll re-post on this thread once I receive it.”

i do do not know where to locate ‘dialogue bubble ‘ icon.
khiak

Thank you clio. You said something that is very important (to me at least)
Bass is not just about hearing. It is about feeling. Part of the rush of a live performance is the visceral sensation you get from accurately projected lower frequencies. This is not easy to do in the home environment. Very few systems do this well but it is vital if you want to feel as if you are at a live performance. Even with string quartets the cellos go low enough to feel to to mention the transients caused by banging and thumping on this that and the other. The "visceral" range is (I'm guessing) from 150 Hz down.
Tim, Magnepans are great speakers. If you remove enough bass from them you can get them as close as 28" to the front wall. Just put some acoustic foam directly behind them. There is this thinking that you have to keep the cross over as low as you can to prevent the woofers from getting up into your mid range. It is easier to blend in with the satellites at higher frequencies and this is particularly true with dipoles which you have just like clio. He crosses over at 100 Hz, not sure about the slope.
Many cross low because they are trying to avoid a high pass filter on the satellites which is also mistaken. Removing the low end from the satellites cleans up the midrange and increases your power handling. You can put a simple 6 db/oct high pass filter on your Maggies simply by putting a cap across the input of your amps the value depending on your input impedance. The equations are on line. 
The reason clio is now feeling his bass is because his subs are now functioning as one driver and the arrival time (phase) is the same across the entire room. His Acoustats are now part of that linear array in the crossover zone. He is now getting his bass as one unified whole not the random output of various drivers around the room. Placing speakers around the room will smooth out response variations but because the speakers are more than likely 1/2 wavelength of the highest frequency you want them to carry apart, they are acting as individual drivers and transients are being smeared. This may be another reason DBA people want to stick with lower x-over frequencies. You can put the subs farther apart and get away with it. A SWARM system can work under certain circumstances. Low x-over points in smaller rooms. Once you pull your cross over up and get into a larger room say 15 X 20 you get into trouble.
What you hear is important. But with bass what you feel is more important.

I forgot to mention that clio has also eliminated 4 of the 5 primary reflections that cause comb filtering in the bass. 
Another way to look at this is that the bass linear array is just a more specific DBA system. It will always require 4 or more drivers unless you listen in a closet.

Hello clio09,
     Wait a minute.  What's your plan?
I thought your plan was switching to a line array with larger subs. Four new subs using 10" drivers sounds like your planning a dba.

Tim
  

I use low pass and high pass filters in my active crossover, Linkwitz-Riley 4th order 24 dB slope. One reason this was chosen is that we wanted to keep deep male vocals out of the subs. The other reason had to do with the resonance of the 8" drivers which we wanted to keep above 100 Hz. This is the reason for a 0.3 cu. ft. box which is stuffed tightly with cotton batting. The last reason has more to do with Roger Modjeski’s ESL design which only goes down to 100 Hz but that is irrelevant to me as I use the Acoustats which he modified to create greater dispersion, but left the rest alone, sort of ;)

I should also mention that the speakers are 4 ft. from the wall behind them, 18" from the side walls, and about 94" apart, which is the same distance to my listening position.