Just showing a little demo of BASS 3D-sounds in action:http://www.youtube.com/watch?v=IKoE-JL7OXg
Took me a short while to figure out why sound apparently on right side was hearing from left speaker. That is because with OpenGL you have to invert Z-coordinate for listener and channels position and orientation. Other than that, just add 3D-flags to creation of engine and each sound source.
This is my implementation of BASS wrapper for fpc and delphi:http://code.google.com/p/nxpascal/source/browse/trunk/src/nxBass.pas