Nice article you had -- very interesting ("JL Audio Gotham g213: Integrating Super Subwoofers into an Ultra System"). I am in the process of integrating subs and I would appreciate some of your insight.
My mains are Klipsch LaScalas. My subs to be are RCF L18S801s. I will have two separate subs, and I have two different locations that are possible: either together mono between the mains, or stereo overlapping and with the mains.
Your article on how you filled in that 100Hz dip was interesting. I have a dbx DriveRack, so I can choose any slope up to 24dB/octave and any frequency, as well as time align. I am in the midst of getting REW (Room EQ Wizard from HomeTheaterShack.com) as well, and this will be the tool to make it happen.
Once REW is up and running, I think I should be OK. Any advice you have would be appreciated. By the way, I liked that trick of reversing polarity at 50Hz until the dip is most severe.
I'd definitely go mono, and close to your mains, and concentrate on getting a smoothly rising response down to 20Hz. Experimenting, measuring, and listening are the keys, and having the patience to stick with a monotonous process until your subwoofers are optimized will determine whether you are ultimately satisfied with the sound of your system. I know that seems quite obvious and simplistic, but the dialing-in process takes time and effort to get that last 5 percent of performance, and that last 5 percent can be the difference between acceptable sound and truly special sound. . . . Jeff Fritz