I have a Creative PCI-E X-Fi Fatal1ty Titanium with WIN7 64bit and I'm using ALchemy with the OpenAL Soft DLL. Below are the steps I took to get 7.1 surround back into the game after having to use soft_oal.dll to keep from crashing.
1. Download the OpenAL Soft DLL from the initial post:
http://kcat.strangesoft.net/openal.html#download
2. Put the soft_oal.dll file obtained from the above site in your Amnesia directory, the same place as Amnesia.exe and Launcher.exe
3. Add Amnesia to ALchemy:
Use Registry Path (64bit Windows):
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Valve\Steam\InstallPath
Install into sub-folder:
steamapps\common\amnesia the dark descent\
Buffers: 4
Duration: 5
The Duration value may vary depending on your system. I started at the default 25 and worked down because sounds, particularly when text was read out loud, would stutter. Setting Duration to 5 cleared this up for me.
*If you're not using a Steam version you can just select "Use Game Path" and copy/paste the installation path from your game in there. You could also use the registry path but that's up to you to figure out.
4. Run the launcher, launch Amnesia, and exit the game. This updates hpl.log and launcher.log with the changes we've made with soft_oal.dll and ALchemy.
5. Go to your Documents folder and find the Amnesia folder and open the hpl.log file. You'll be looking for the list of sound devices that the launcher sees, it'll look something like this:
--------------------------------------------------------
Initializing Sound Module
--------------------------------------------------------
Initializing OpenAL
Available OpenAL devices:
0. DirectSound Default
1. Speakers (Creative SB X-Fi) via DirectSound
2. WaveOut Default
3. Speakers (Creative SB X-Fi) via WaveOut
4. SPDIF Out (Creative SB X-Fi) via WaveOut
5. No Output
6. Generic Hardware on Speakers (Creative SB X-Fi)
7. Generic Software on Speakers (Creative SB X-Fi)
8. SB X-Fi Audio [0001](OpenAL default)
Trying to open device 'Generic Hardware on Speakers (Creative SB X-Fi)'... Success!
Number of mono sources: 63
Streaming setup: 4 Buffers x 262144 bytes each
As a result of using ALchemy, we have "
Generic Hardware on Speakers (Creative SB X-Fi)" as an option.
6. Open main_settings.cfg from your Documents\Amnesia folder and where you see "Sound Device=", put the number of your "Generic Hardware on Speakers". Mine is "6" so mine looks like: Sound Device="6". You can also change Max Channels to 128 but I don't know if that does anything. Save changes made to the config file.
Now run the Amnesia launcher and notice in the "Sound options" tab that the "(Unsupported)" hardware device is selected. You won't need to make any changes to that from there. Run the game and you should have proper 7.1 surround as you would have had with the now unsupported X-Fi OpenAL
I don't get any crashes with this so it should be fine for long-term use.
Edited for better/clearer instructions.