According to Tom Nousaine, corner placement of a sub is generally the best position. This can be flush against a corner or out a few inches so long as we're not talking about a couple of feet. This is not to say that all corners are equal. For example, it should not be in a corner that is symetrically opposite (kitty corner) a room opening. In the one example that Nousaine found where direct corner placement wasn't the best (an open loft), the best response was obtained 2 feet out from either one of the two closed corners. A closed corner was taken to mean one that had 5 feet of more of solid wall to either side of the subwoofer. In terms of what might be considered the best listening postion, Nousaine has found that is generally between the long walls and about 5 to 6 feet from the wall located behind the listener. Further, the subwoofer should be crossed over below 100 Hz. The goal, as TN sees it, is to obtain the flattest frequency response. He bases his opinion on measurements that he has done on a variety of rooms over 3 years. His finding, after measuring a variety of rooms (low frequency response maps in 2 foot intervals) with different subwoofers, supports the general statement that placing a subwoofer in such a postion provides the following benefits. 1) excites all the modals in the room which gives the flattest freqency response at all listening positions. A consequence of this is that phase response and signal timing are also optimised. While some may take issue with that of signal timing by arguing that arrival time can be affected by placement, consider that studies have shown that approximately 100 milliseconds is needed @ 100 Hz which is about 100 feet. If you consider the room you're putting your subwoofer in, unless you're dealing with distances that long, then you haven't a problem. Other positions will cause some room modes to be not excited and this results in suckouts which are holes in the frequency response. 2) provides the deepest extension 3) maximizes output As a side note, he also found that many mapping programs, such as CARA, gave erroneous results and predictions when dealing with low frequencies. They correlated poorly, if at all, to the actual experimentally measured results. Consequences of using such programs blindly might suggest placement of subwoofers in decidedly non-optimum locations. Further reading, if anyone chooses can be found in the following 2 publications. They may be available at your local library through the inter-library loan program. January 1995...Stereo Review..."Subwoofer Secrets" June 1996...Audio..."Placing the Bass" As an additonal resource, I've taken the liberty to quote from an article that was published in Sound & Vision by TN.