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@mijostyn re: sub setup I set mine up per Earl Geddes. He actually recommends at least 3 and to have one above the midline level of the room if possible, see pg. 236. I only have two and use the opposing corner setup:

@phusis , the main issue is that most of my customers are not willing to expand the size of the control / mixing / listening rooms to accommodate the required size of a horn subwoofer in order to get a sufficient efficiency boost at the frequencies the subwoofer is expected to cover. Even for a subwoofer I need to be careful about dispersion as well.

@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.