Hi danr,
Randyman's suggestions are good (I'll have to go back to May to see what I said!) but overall, placing ANY speaker in a corner alters its sound, almost always in an unflattering manner, the exception being a subwoofer. That's because the three intersecting surfaces--two walls and a ceiling--form a type of corner horn, thereby horn-loading the radiated sound from the QS4s.
In the old days (1950s) when I was a kid, there was a type of speaker called a "folded horn", which was intended for corner placement--it used the aforementioned effect of a corner to strengthen and reinforce low-bass output, which was very effective. But power amps then were tiny, tube, and underpowered--the one I built for my dad was considered huge (25 watts mono). So if you wanted real-life volume levels, you used a speaker design to get the highest SPLs for the smallest number of watts input. (the midrange and tweeter of that folded horn I built were also horn-loaded).
Folded horns are still built, and have their fans, but for domestic high fidelity, the are, in my judgment, awful. Very colored, strictly low-fi by comparison to modern, well-designed speakers.
So my advice is, except for the bass reinforcment that corners offer for subwoofers, keep ALL speakers out of corners!
Regards,
