Ok, I don't post here much and one of my posts that I posted a while back was stating that when I bought the MicroPro 4000, the bass was loose, exaggerated, and very weak. The driver flexed a lot, and produced minimal usable bass. Upon the recommendation of other CP members I tried changing locations, receiver settings, sub settings, and numerous other things. With Polk's room correction, I dialed it in a little but the bass was still not what I expected from a $1700 sub. Anyway, long story short, I bought another MP4K from another member, and hooked the two subs up. BLAMO!!! Bass for days. Clear, precise, awesome bass. I thought it was because I now had 2 awesome subs. Skip to present time. Last week I cut out some sheetrock and ran all my wiring in the wall and patched the holes. Hooked the subs back up....sounds like a$$. You know why? LFE. If I use the LFE input on the subs, the sound produced is subpar at best. Plug the sub cable into the "Line In"...perfect sound...deep powerful bass. Why? I haven't been able to find a clear answer to my question. I know with all the experience in CP someone will be able to educate me...thanks in advance.