Hardly any sound Bass from Subwoofer of my 2.1channel soundbar

Dear Friends, I recently bought a F&D 2.1 channel speaker system with a 6.5 subwoofer. Now the problem is whenever I am hooking it up with my Laptop / Phone, there is hardly any sound output coming out of the subwoofer. The bass knob is on the Subwoofer and the volume know is on the soundbar. I have wired it as mentioned in their manual.

Below is the link providing details of the product:

http://www.fendaindia.com/products_view.asp?id=47


Please help as I have tried everything to get the sound output from the subwoofer while connecting to Mobile Phone / Laptop with no luck really.

Regards,
Pijush