Confirm all wiring connections, just in case of a silly mistake or bad cable. Check set up and levels in menu of Denon. Swab out center channel speaker with any other speaker just too make certain your NHT center is indeed working properly. Good luck.
Center Speaker Suggestions??
I have a 5.1 system with all NHT speakers driven by a Denon receiver. The center channel (which does the yeoman's work when playing Blu-Ray,) is unintelligible. When using my Denon wireless headphones, the sound is glorious - very easy to understand dialogue... so I'm thinking something is not right with my NHT midrange speaker. Does anyone have a suggestion?