Sub out no sound.

[Dave P]

Hi all, quick question.

I have a sound card with three 3.5mm mini jack ports that came with the pc. For yonks I've just had a pair of tiny trashy speakers connected to the line out jack. One of the other jacks can be configured for a sub and I fancied adding a bit of weight to the sound so hooked up an old book shelf speaker with a 20 cm cone to the sub jack. I used an old mini jack to stereo lead that has three cores; left, right and a common return. I tried either the left or right with the common return and I can't get any sound.

I'm sure there is something very simple and fundamental I'm not aware of as to why this won't work. If someone could enlighten me i'd be very grateful.

Thanks.