The Harman paper did take the concept further. Nevertheless, multiple subs up front has alot going for it. Anytime I have heard subs with upfront placement it sounded very good, though the visual impact may have been a factor. I like his idea that "reflections from the side walls will continue, creating a line source of infinite length". It helps explain why that placement always sounded good.
With duals in the corners, its more hit and miss than suggested in Ohman's article. It can contribute to boomy bass from reinforced peaks, especially in smaller or square rooms.
I agree completely with this. Since corner placement increases SPL for the room modes, and is not uniform accross the full frequency range for the sub. You get more SPL at the expense of flatness, generally- but each room and sub combo is different so you just have to experiment. Randy will vouch for this
