Hi Fred,
Unfortunately, X-Plane does not support splitting its sounds into multiple audio devices.
Are you using a multiple PC set up running different copies of X-Plane and networking them together to get your sound work around? If so, please describe each set up in a bit more detail for me to investigate.
If you have found another sort of work around, we will not be able to help troubleshoot it as we don't support hacking the sound in any manner.