Grimrock

I didn't quite notice it at first, but now it's become annoyingly apparent. I have my audio set to 7.1, however it only give me the full experience in some areas at random times. It's not my setup, or my sound card. I've tested it with other games, and tinkered endlessly. I'm wondering if anyone else has had this problem, or has been able to resolve it. Any suggestions on how I might go about fixing said issue would be much appreciated. When it's not 7.1, it's still surround, just seemingly without subwoofer. Also, rather than constant ambient noise, rear/back speakers only pick up certain things like movement or attacks.