OpenAL Soft can't give you 5.1 where DS3D did provide it. OpenAL Soft by design uses center channel ONLY for dialogues and never uses LFE channel.
So you got a 5.1 actually downmixed to 4.
Edit: read this https://forums.freebsd.org/threads/snd_hda-op … ubwoofer.33032/
Hello, one of the few to care about proper use of the LFE channel. I found this on my endless search to find out why OpenAL NEVER uses the LFE channel [in games]. I believe I have determined that this is primarily an OpenAL issue and that for some reason PulseAudio doesn't do bass redirection with OpenAL games.
So I first came across this issue when I was playing Amnesia in Ubuntu. I had played Amnesia in Windows and had LFE but why not in Ubuntu? Come to find out that I was using bass redirection in Windows so I disabled that feature and went on an LFE testing rampage in Windows-based games. No OpenAL games used the LFE channel while DirectSound, XAudio2, and FMOD games used the LFE channel; some games using those APIs didn't use the LFE but some did which leads me to believe that it's up to the programmer(s) to enable that feature. Perhaps OpenAL outright lacks the ability to route low-frequency audio to the LFE or perhaps it would require a lot of additional programming to implement and no one cares enough to do it in their game.
I went back to Ubuntu to figure out how to do bass redirection and what I found was that, even though I successfully had bass redirection working in music by enabling LFE-remixing in the Pulse config file, it wouldn't redirect bass in Amnesia (with default PulseAudio as the device in Amnesia's settings). Pulse should be able to redirect the bass if the audio is being routed through it but maybe it's not entirely understanding OpenAL and dropping the ball.
We know that the LFE is available in OpenAL because it plays that channel when you test a 5.1 wave file through it (I've at least done that in Windows with the dev software) but utilization of the LFE seems totally absent in games so it seems the only way to get any subwoofer activity from these games would be for the OS's audio system to do bass redirection.