Receiver and sound question

[avinfoman]

New to posting so excuse if its an idiotic question.. i have a Harman Kardon avr247 receiver. First of all what do the DB levels mean?? I virtually get no sound from my speakers at the low DB levels. I can go over the 0 DB level point when playing my PS3 and pretty much watching tv etc.. What does this mean as far as my receivers speakers go? Bad combo, or good being the fact that they can handle going over that level and still sound good ??

Also if I should be getting more sound at the lower DB levels, is there an adjustment I need to make?

Thank you