I have read a lot of threads on many forums that people have noticed difference in quality of sound when burned at higher speeds and on lower speeds such as 8x the quality is much better. I personally have noticed "some" difference not much only when u hear it thru and good set of headphones but thru normal speakers sounded the same to me but I do think it is true, I'd prefer 12x to burn audio cd's not too slow and not too fast, right in the middle.

Hope this helps

Alam