No analog surround sound on KODI using IONITX Motherboard

Hello everybody!

Although my problem is with audio, I suppose this is the right forum to post it because it’s not music-related.

I have just installed OpenELEC 6.0.3 x86 Generic (Intel/AMD/Nvidia) build, which includes the last version of KODI. So far, everything is working fine except for the surround sound.

This is my hardware setup:

– IONITX F-E Motherboard
– Creative Inspire P5800 Speakers

I extract video through the HDMI port of the motherboard (everything working fine on this side). For the audio, I’m using the analog 3.5 mm conectors of the integrated motherboard audio card, plugging them into the speaker’s subwoofer. I mean the classic three-color 3.5mm mini-jack audio cables, like this:

The thing is, no matter the configuration options I choose, I only obtain stereo sound (rear speakers don’t work). Prior to installing OpenELEC, I was using Windows XP on the same hardware and surround sound was working fine, so I suppose this is a driver / software issue. Could you give some guidance on how to fix it?

Thank you very much,