Arris Dcx3600-M Spectum cable DVR (had same problem with Directv)
95% of channels work fine using receiver to TV with HDMI. Other 5% can only hear audience with Wheel of fortune voice is very muffled was same with Directv.
WOFLHD local FOX station for superbowl – Crowd noise fine, voices muffled
ESPNHD – muffled
PBS, 2 stations are muffled
Pioneer VSX-1022 Receiver
Pioneer L-R speakers
Definitive 1000 Procenter
Klipsch subwoofer KW-100
Since you don't have a center speaker those channels that send voices to that speaker don't have one for the sound to come out of.
Check that the receiver is set to no center speaker.
Check the audio menu of the cable box. Try changing the audio output.
Try a different surround sound mode on the receiver.