CPU Considerations for 3-D Buffers
Software-emulated 3-D buffers are computationally time consuming. You should take this into consideration when deciding when and how to use 3-D buffers in your applications.
Use as few 3-D sounds as you can, and do not use 3-D on sounds that will not really benefit from the effect. Design your application so that it is easy to enable and disable 3-D effects on each sound. You can set the Buffer3D.Mode property to Mode3D.Disable to disable 3-D processing on any 3-D sound buffer.
You can also ensure that 3-D processing is suspended on buffers that are too far away from the listener to be heard. See Minimum and Maximum Distances.