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@thespeakerdude , I do not care if you can produce a complicated enclosure or not. I am not limited by financial and space confines. I can build whatever I want. That is the beauty of DIY. If you have the tooling, you can make just about anything. I already have a technique for building cylindrical enclosures and the beauty of it is that the wall thickness varies continuously repetitively between two inches and 1.5 inches 10 times. 

@phusis , that is absolutely correct. The smaller the excursion the lower the distortion. It is why bigger drivers have less distortion than smaller ones. The problem with horn loading is size and the difficulty building a large dampened enclosure. The alternative is using multiple drivers. Every time you double the number of drivers you increase efficiency by 3 dB which requires 1/2 the excursion. In a 16 X 30 foot room 8 12" drivers in corners and against the front wall will do admirably. 

@kota1 , Earl is trying to do the distributed bass gig in his own way. Drivers against a wall on the floor are 3 dB more efficient than drivers not against a wall. Drivers in corners are 6 dB more efficient. More efficient drivers = less distortion. It is also important for the drivers to be less than 1/2 the wavelength at the crossover point apart. Say you want to crossover at 100 Hz. That wavelength is about 10 feet. You do not want your subs more than 5 feet apart. Within 5 feet they are acoustically operating as one driver. If you look at my system page, the front wall is 16 feet. The subwoofers are 4 feet apart forming an infinite line source. This makes them even more efficient and sonically more powerful. 

@mijostyn , thanks. I EQ them with Audyssey in my processor. I have a question for you. I run two subs because my processor has two sub outs. I would still like to add a third one as Earl describes. I am thinking of getting a DSPeaker or miniDSP to EQ them. Should I skip it and just stay with two? I don't need more volume and the bass is satisfying. I am just wondering if it would be OTT good if I add another one. Thanks

@thespeakerdude , you can see how my subs measure without room correction in the graph below (blue frame is before), thoughts? The numbers in the scale are cut off when I uploaded it from PDF.

@kota1 , You do not want to add another processor. The best way to do it is add 2 subs, one to each channel and stay with a 2.2 system which is what I do, two subs per channel. Remember the main speakers are equal volume at the crossover point and can be included in the distance factor but if you have a point source system the subs of each channel should be right together but the channels separated by 1/2 the wavelength of the crossover point. You could also put them way apart like some people do with a distributed sub system. My own preference is to put all the subs on the front wall, but I also cross at 100 Hz. 

You need to include Hz on the horizontal axis and dB on the vertical. We are need points of reference. Change the size of the file to fit. The subwoofer files are typical. You see the room Modes. Room control is a beautiful thing.

@mijostyn

You do not want to add another processor.

That sounds right, I am going to shelve any tinkering with more processors, etc. I think I’ll go in the opposite direction and try 2.0 with no subs and no dsp when I get the new Sony preamp delivered and will post how it goes. The Paradigm passive 40's go down to 45 hz or so. The active version I use go down to 32 hz which should be fine for music.