I think its how each sub interacts in that same room. Before I bought the EP600, I had an Axiom mfg sub with two 10" drivers in the same cabinet - one forward firing, and one down firing. The ports were down firing as well. It seemed that I could drop that thing just about anywhere, and the modes weren't a big issue.

In the same (current) room, I've had a heck of a time placing the 600. Now, there is no comparison in sound quality - it goes deeper with far, far more impact, and is much tighter with music. The thing is simply amazing in that size of room.

Shawn

Epic 80/600 + M3's + M3 Algonquins + M2 Computer + EP125
I think I'm developing an addiction.