Rear speakers only playing during turn 10 intro[PC]

Hi,

I am getting nuts because my rear speakers are not playing any sound in game. When I launch Forza 7 (same for Forza Horizon 3) I hear something from my rear speakers during the Turn 10 Video, but after that I never hear a tone from the rear speakers again.

Normally the issue is connected to my windows setup, but this time I think my settings are ok, and the issue must be related to Forza somehow.
I also retested my surround sound with Witcher 3, and there it was working fine! And I am 99% sure the surround sound was already working in Forza Horizon 3 earlier.

My hardware setup is maybe a little bit special. I am using a Creative SoundBlaster X-Fi with driver from 01.09.2015 Version 6.0.240.12 by Creative Technology Ltd.
I have connected my Yamaha RX-V450 Receiver using a optical digital cable.
In order to be able to get proper 5.1 sound to my receiver I have activated the Encoder for Dolby Digital. (not an actual screenshot from my system)

The windows speaker settings are set to 5.1 (not an actual screenshot from my system)
speakers

In Forza audio setting I also enabled optimization for 5.1 I also tried stereo and 7.1 but I never hear something from the rear.

Any ideas what settings could be wrong, or maybe if Forza does not support my setup, are highly apprechiated!

Thanks a lot.

anyone, any idea? still not working…

Have you tried making SPDIF Out your default device? Right now it looks like your default communications device which usually means microphone and headset, and hence 2 speakers only.