Confirmed problem is with the new iCue software.
Completely uninstalled the 3.23.66 software.
Played various installations of the game without the iCue software installed and windows drivers and I never lost sound to the rear when I looked straight ahead or any other direction.
I performed a clean install of the iCue software, flew various installs of IL-2 1946. As I flew straight ahead with three other aircraft in finger four formation I would lose sounds to the rear (surround) after 5-10 seconds. If I turned my head a few degrees left or right the sound came back to the previous volume. As long as I move my head around the sound remained. When I looked directly forward the rear sounds disappeared again. With the version of the iCue software and driver I had installed this problem did not occur. Only when I install v3.23.66 and the driver does this occur.
Where can I get immediate preceding version of iCue software and driver?