Surround sound was limited to a single plane until Dolby Atmos and DTS:X added height, allowing the audience to immerse itself in a more realistic three-dimensional acoustical environment.
Dolby Atmos and DTS:X both can work with lossless high-resolution audio. Their biggest advantage is when used in conjunction with a 7.1 channel system plus in-ceiling speakers. This is referred to as 7.1.2 (two ceiling speakers) or 7.1.4 (four ceiling speakers).
If using two ceiling speakers, the speakers should be placed just slightly ahead of the main listening area with one to the left and one to the right. If using four ceiling speakers, two speakers should be placed slightly ahead and two speakers placed slightly behind the main listening area, again one speaker from each pair placed to the left and the other to the right.