Do you mean the dialogue doesn't sound crystal clear and dynamic ?
Is dialogue volume too low or unclear?
Does the Center speaker make a crackling noise sometimes?
What is your Center Speaker Channel Level setting - is it the same level as the other speakers or did you increase the Center channel level +3dB above the other speakers?
Center in particular has been the most difficult to dial in ever since getting rid of my old receiver. Voices sounded thin and unnatural or boxy, sound effects would sound compressed, strained.. so I did a few things before buying the new Prime Center: moved the speaker up to the front edge of the cabinet, placed some room treatments (one large 2x4' panel of 703 behind the couch, 2x2 panels on the wall behind the mains, one small 0.5x2' panel behind the center). I also elevated the speaker itself and acoustically decoupled it from the cabinet with a foam pad. All of these helped but it still wasn't right (and through two new top tier receivers at that).
So at that point I bought the Prime Center. Re-ran YPAO, copied EQ over to manual, fine tuned (center only) by ear, adjusted tone controls (basic bass and treble controls on the Yamaha: -1.5db treble, +2.5db bass), then checked levels against my SPL meter. Re-adjusted to match everything at 75db post tone and EQ corrections. Because the Prime is a bit more sensitive than the SCS's it's ending level setting was a few db less than the mains to achieve same SPL at the MLP.
Oh I also notched out the 8khz area with a pretty narrow Q to help reduce the over emphasized sibilance I was getting.
Both the Marantz and the Yamaha seem to really jack up the treble and HF on my center so I have to really tamp that back down.
Right now it's about the best it's sounded yet and although maybe still not as natural (with voice) as I'd like, I'm not sure what else I can do to add improvement. All the above seems to be the best sequence and combo of things out of the multitude of things I've tried.
So, in short - Prime is decent. It's getting the job done, albeit with some heavy manual tweaks but don't think it's an improvement that reflects the $300 I spent on it. I'd give it maybe $50 worth of improvement over the SCS if I were to assign it a monetary value.
