Cierto Element
Adecuados para poner detrás cuando es imposible a los lados del punto de escucha o estás cerca de la pared trasera.

http://www.polkaudio.com/home/faqad/...icle=placement

For these reasons, surround speakers work best when elevated at least two feet above the seated listeners' heads (a height of six to seven feet above the ground is considered normal), and mounted on the side walls in line with or slightly behind the audience (figure below). If you are using front-firing speakers, they should face each other so that the sound is projected over the listeners' heads.



If your seating area adjoins the rear wall, or if you cannot place speakers on the side wall, you'll have to position the speakers on the rear wall (Fig. X). In this case, bi-directional (bi- or di-pole) speakers are recommended, since they will produce the most diffuse effect. If you use front-firing speakers, do not aim them at the audience as one would a front speaker, but point them straight forward so the sound projects past the audience (figure below). Another option is to mount in-wall speakers in the ceiling, aiming them downward at the listening area.