Hi - not sure if i've posted in the wrong tread , but i really need some advice on how to connect my old pc speaker ( Altec lansing ADA 885 to my xbox or LCD monitor)

my current setup

Xbox with single HDMI cable LCD bravia S400 , connect ADA 885 thru the LCD headphone jack & the sound suxx ...

I know the ADA 885 has a digital input jack but i have tried a few types of cables to output from the R/L output from LCD to the digital input but to no avai...

any sifu out here on the same setup ?