If you’ve got full Dirac live setup file, you can alter the gain just for the centre channel across voice frequency range. The Dirac if properly measured should sort that out for you though, as it measures the signal through the channel before amplification. I.e. it shouldn’t affect one source and not another?
The UMIK 1 calibration mic cost and time to set up is worth the effort. I got much better calibration than the box included/ standard mic; transforms the sound placement and balance.