Generally speaking, the larger the vertical spread between the front drivers, the more distance the speaker needs for the sound of those drivers to integrate. A small bookshelf speaker should be listenable at a close distance, maybe half a meter or closer, especially if its designed to be a near field monitor. A coaxial speaker like the Kef LS50 should have great integration at any distance, since there is almost no distance difference between the woofer and tweeter. On the other hand, a speaker like a large 3-way tower may need as much as 2 meters and sometimes more distance. The large speakers made for commercial cinemas can need a lot more than that even.