14bit audio is quite easy.
Create two 8bit sample buffers the same length, load one with all the highbyte data of the 16bit sample and load the other with the lowbyte data. Set the volume of channel 0 to 1 and the volume of channel 3 to 64 then play both samples back at the same time with the highbyte data in the full volume channel and the lowbyte data in the volume 1 channel. That gives you your left 14bit channel.
Do the same for channels 1 and 2 for your right audio!
