No can understand....

I have a Denon AVR X3100 and have set it up using their setup preceedures (very easy).....I have the speakers in a 5.1 surround sound configuration. Anyway, often the dialogue is so fuzzy: blurry, its very difficult to even understand it’s English. (I should have revealed that the speakers are floor standing NHT speakers on the left and right,with an NHT center and in ceiling speakers (don’t know the brand) for the 2 rears) and Outlaw Audio sub. There is a graphic equalizer, (not much help) and there is a dialogue boost/cut (likewise not much help). I'm using midlevel Wireworld HDMI cables..... Any suggestions?