"I have a feeling that JBL is protecting that horn with their crossover network. I have heard that the drivers a built like tanks and one supplier has never heard of anyone ordering replacement drivers (woofers) but that horn is another story, I bet they are filtering the heck out of it. It runs parallel to the LFE section on the bottom so how much power is actually getting through the network? Hmm, sounds like a bi-amp is in order??"
you may be onto something there as i can't for the life of me figure out why those woofers wouldn't be performing as you want them to.
i'm not completely sure how having the network in front of the woofers degrades (or not) the effect that you are looking for. given that they are low passed fairly high up, i'm not sure it would be a problem, but who knows. a harman/jbl guy who switched his everest to active indicated that it really tightened up the bass, but they are .1 with a relatively low cross on one of the woofers. so again, some evidence, but who knows.
one other thing, based on your pictures, the placement of the main units is such that you are going to get a big time cancellation from the side wall and the rear wall right in the midbass region. when you are 1/4 wavelength from a boundary, you get a cancellation.
here is a good note:
so at a minimum, move them out of that spot before making judgement calls.
also, urapnes (i still have a hard time typing that lolz) suggested putting some eq on them in the 100-200hz ball park. that might not be a bad idea.
also, one thing further, given the different distances from the mains and the subs to the listening position, the mains will need some delay on them, so everything is time aligned.
interestingly, you might also try putting a little bit of negative eq on/around 500hz or so. not sure why, but lowering that region can make drum beats seam to have more hit.
[btw, i just the kind words a page or two back...thanks guys. :-)]