With today's technological advances in the world of home theatre, we have progressed from stereo, 2-channel audio to fully high-definition 7.1 channel surround sound. 7.1 channel surround sound is a step up from the long-time 5.1 channel audio standard as it adds two additional speakers, surround back left and surround back right. With a Dolby Digital 7.1 surround sound system supporting Dolby's Pro Logic IIx technology, you can convert your 2.1 stereo audio into full 7.1 surround sound. Dolby is currently the only technology that can convert 2.1 all the way to 7.1.
Turn on your surround sound system and 2.1 stereo audio source.
Switch the input mode on your surround sound system to the input you have the 2.1 stereo audio device plugged into -- for example, A/V or stereo.
Select the "Pro Logic IIx" sound mode by pressing the "Sound mode" up/down arrow buttons on your surround sound system remote control. Once selected, start playing the desired audio on your 2.1 stereo audio source. It will now be converted to full, rich 7.1 surround sound and start playing through your system's speakers.