Hi!
After the patch 4 update, I can hear all sounds, music and effects - but no dialog, when using loudspeakers.
I am only able to hear dialog when using a headset.

I have checked for latest soundcard drivers
I have tried different audio options when using loudspeaker: home theater, monitor, headset, 3D headset
I have set all in-game sound/music/dialog to 100%
I have no mods installed, and I also tried uninstalling the game and re-installing it, in addition to several PC reboots.

Any tips?

I have a 2:1 loudspeaker setup, with two loudspeakers and a subwoofer attached to a Creative SoundBlaster X3. I'm using the same setup with all my other games, and haven't had this problem before.

I have same problem except dialogue is not working with loudspeakers nor headphones. I tried changing various sound settings in WIndows and drivers without any effect.
All I can hear are ambient sounds (city background, crows etc.)

If you guys are using 5.1 or 7.1 speaker settings, check if you have enabled the "Center" channel. Basically, dialog in games tends to use this channel and if it's disabled, there won't be any dialog sound. Switch to Stereo to prove that this works!

Super late reply, I know, you might have already figured this out but, I only recently bought the game and discover this "bug".