As with every speaker, there is no such thing as a minimum or maximum of something. Every speaker sounds more spacious with more image depth and air, if it is not close to a rear wall. It is of course possible, as with any other speaker, to put our speakers right in the corner. But then you lose much of their incredible sound staging abilities, especially image depth. With most other speakers you lose less, because they in the first place could not create a similar imaging performance.