crossovers

[brett_day]

Hey Guys

I am hoping someone will be able to explain crossovers to me. I have researched the topic and from what i understand, whatever you set the crossover too, anything below that setting will be sent to the sub?

The problem i am having is that my sound, sounds flat. There does not seem to be much bass period. With my old sony 720 there was an option to set the speakers to small, which fixed this very problem. however on the onkyo 605 there is no such option, so i am assuming i have the crossovers set incorrectly! My front speakers sound incredibly tinny, and not much seems to be reaching the sub, this was especially felt while playing cod4. any suggestions?