I have a Yamaha receiver that I used to be able to activate the DTS mode and get sound. The speakers at the time were left and right front/rear speakers with center channel. Connection for audio is toslink optical to. Panasonic blu-Ray player. Currently I only have the center and front left and right speakers, still using a TOS link connector, but connect to an Xbox 360. When I now activate DTS I do not get any audio. The blu-rays I’m playing have DTS as an option. Any ideas what I need to change? Is the problem with the Xbox or that fact that I know longer have rear speakers?