Windgat

hi, new owner, and new member here need a bit of advice if anyone can help me, i just fitted my own woofer into the boot of my 2002 SE, and although it's working, the volume control on the stereo doesn't work on it. if i turn the volume off, the woofer still keeps gong, at the same level, and if i turn the volume up, the same happens. i may be thick, but i am completely stumped! Any Ideas?