Go into the setup and set your crossover to 80hz (THX standard), and set your main speakers to small if you have that option. Some music requires little help from a sub. Older recordings have little if any bass in them, so go buy some modern rock, or rap, what ever blows your skirt up
Now, go to your sub. turn the crossover all the way up to max or turn it off if it has a switch. Turn the gain DOWN. Next, throw in the new Jay-Z CD (just kidding) and turn it up little loud, but not like a concert, and begin turning up the gain till you hear and/or feel the bass.
I hope you now have bass in your music. I love running my system as bassy as I can without muddy midrange. I'm addicted. Everyone who hears it thinks my system is awesome, so I must have a trained ear or good luck