We have a fix!
I e-mailed the same issue I had on Fantasy Wars to 1C and they came back with a fix which I've tested on Elven Legacy too. It works for both games:
1) open tbm.in file with notepad located in your \Elven Legacy\Data folder.
2) Add the line "setf ~cl_force_soundcard" (Without speechmarks) at the bottom.
Boot up and enjoy the sound on your headphones!