Audiomaze, I recently added a Swarm to my dedicated listening room. As usual, I found that using REW as a guide got me to optimal results faster than using the sub crawl technique or published formulae for multi-sub placement. My mains go pretty low. They are down 3 dB at 27 Hz but have decent output down to about 23 Hz. So, in a sense, I have six subs, two of which are in fixed positions.
All that said, my final configuration was as follows:
I ended up with one of the 4 Swarms subs in each room quadrant. Right front, right rear, left front, and left rear. I had one sub in the left front corner angled away from the corner, firing down the left side wall at an angle. Another sub was placed in the right rear corner, firing directly into that corner. A third sub was placed along the right side wall about 1/3 of the distance from the front wall to the back wall, and this was firing towards the rear wall. This sub was elevated about 30" off the floor. Sub 4 was placed immediately behind the listening position, firing into the left rear corner from a distance of about 6 ft. All four subs were out of phase with the mains.
As a rule, the direction of fire of those subs in a corner made a big difference. For those subs located away from a corner, the direction of fire made a small difference.
My room had been very carefully laid out and treated before installation of the Swarm system. It took a great deal of care for me to install the Swarm in such a way as to substantially improve frequency response at the listening position, but I finally got it, and boy, do I like the end product! No doubt this was one of my best investments of time and money ever.