How to play wav files in different chanels?

My task is to play some WAV files in different sound card chanels in same time. The chanels are: front left, front right, rear left and rear right. Now I'm using playing sounds via DirectSound secondary buffers. I set the position of sound sources using IDS3DBUFFER.SepPosition routine. I use such coordinates(in terms of x,y,z):(-0.5,0,1)-front left, (0.5,0,1)-front right, (-0.5,0,-1)-rear left, (0.5,0,-1). Coordinates of 3D listener is defaults. And I have such situation: acoustic division between front and rear is excellent, but between right and left is bad. In other words I hear the part of left chanel in right and the part of right chanel in left.
Please help me to solve my problem.

ok, i might not tell the right answer, but just a small thought i had when i saw the coordinates.

why don't you change them to
(-1,0,1)-front left
(1,0,1)-front right
(-1,0,-1)-rear left
(1,0,-1) rear right

might work.

I have tried to set such coordinates. But in this case the influence of chanels on each other is more appreciably. And I cann't understand why. :(

The attenuation is probably looping the sound around to the other ear (if you see what I mean).

Try making the attenuation higher, and moving the sound closer to the ear.

R