Topic. From what I've read, this was quite easy to do in XP, but Windows 7 is set up so that it has only one "default audio device" and it shuts any others down. As it happens, I'm using a headphone soundcard (Xonar Essence ST) but would like to be able to take advantage of the onboard audio (Realtek) so I can send audio to a subwoofer.

It needs to be pointed out, if it was not obvious, that one does not easily "split" the audio coming from a headphone soundcard since it is basically a headphone amp, and modifying it in any way would utterly defeat the purpose. So, no analog solution is going to work here. I literally do need to force Windows7 to send audio out both devices.

Closest I have come to a solution is via an app called Virtual Audio Cable, but as far as I can tell - and admittedly I've been held back considerably by inadequate documentation - it actually cannot address my specific need.