Thanks I'll try. With other games the reverb works so it could be a problem for some, I don't know... maybe you could test if, with these two games, you too have no reverb.
EDIT
The solution suggested, in Serious Sam doesn't work. In Far Cry it seems like that option just applies reverb to everything, even the intro so it's not the right solution. There must be something wrong with DSOAL in these games.
EDIT2
Earlier I wrote that in Far Cry the audio with DSOAL was better than in Alchemy (although there is no reverb). Now comparing it to audio without any wrappers, it sounds the same as DSOAL, I can't hear any difference, and the "Hardware mixing" and "EAX 2.0" options can be activated without a wrapper (in all other games, including Serious Sam, without DSOAL or Alchemy, EAX is grayed out). DSOAL is loaded by the game, but it appears to be doing nothing. I want to specify that with other games, the difference between EAX on and off is noticeable.