3 ohm speaker

I have a 3 ohm sub woofer. I am trying to make a driver for it using a transistor, a tip120 darlington transistor from radio shack. It is rated up to 8 amps and I running the speaker at 5 volts (the power supply can handle up to 4 amps) when I tried this the speaker made a crackling noise and could not make all the sounds. Does anyone have and circuits or advice on how to do this?

with my setup, The speaker is apparently only using 50 mA when I measured it with a multimeter.

Check on a link: http://www.redcircuits.com/index.html#Audio