Well, I went the “easy” route for the subwoofers that I just acquired, and with my minimal work, I must say that I am impressed. I acquired 2 Martin Logan Balanced Force 212 subwoofers, and placed them just inside (medial) to the Sound Lab ESL’s, and slightly closer to the front wall (about 24″ away). I set the low pass filter at 41 Hz, and just played some vinyl. The low end was much smoother, and more rounded, with a full sound, as opposed to the slightly thin sound that the SL ESL’s are otherwise predisposed to at the lower end. I didn’t bother with any real DEQ, etc yet or any HPF for the SL ESL’s. Presently, I’m content and impressed with the improved SQ of my system just by simply adding subwoofers.
I did note that when I moved the subwoofers out into the room more, that the bass disappeared, as some interference was obviously occurring. Fortunately, the initial placement simply worked.
One detractor: warped records, even if only slightly warped produce a huge low frequency signal that is unlistenable with the subwoofers.