Magnat Subwoofer Connection Problem

[Abnormally Skilled]

Hello guys,I just got a magnat subwoofer and want to connect it to my PC.When i connect it to my pc via a 3.5mm jack and set it as a subwoofer.It doesnt work,but when i connect it as a front speaker it does.The thing is that i what want my magnat for bass and my monitor and other speakers for the music.What can i do in order for them to work?I tried using the only monitor's speaker for music and still doesnt work!(using hdmi)
Do i have to connect it to a diffrent port?(I tried connecting it to the green which is the only port that the sub works but disables both the monitor and the other speakers)
I HAVE A GIGABYTE AN H97 HD3 motherboard with stock sound card(Realtek® ALC887 codec)
----->http/www.gigabyte.com/products/product-page.aspx?pid=4954#sp
Thanks

 

[americanaudiophile]

The subwoofer and center outputs are shared on the orange stereo jack. If the cable has two outs on the speaker end use the other one.
If there is only one out on the speaker end it may be the wrong cable (mono mini plug to single RCA).