5.1 sound problems?

Question

ASUS

There is an Asus Maximus VI Hero mother and a 5.1 system. When you connect speakers to the back panel, when testing them in Rialtek, everything works, but when playing music in VK, on ​​any players, only the front, sub and center silence work. But when I reconnect one of the jacks to the front panel everything works fine. I do not connect rear speakers, because. nowhere to put them. And then it turns out the front is connected on the front panel, and the sub / center on the back. Who faced such problem? How did you solve it. Firewood is worth