Question: What is the compatibility between the older CD-RW media (1x-4x), and the "high speed" media (4x-10x)?

Answer: Older CD-RW media design is insufficient to deal with the demands of high-speed recording. Thus, one consequence of accelerating CD-RW is that it requires a new blank disc. However, due to technological constraints, it's not possible for a single type of disc to support the full range of recording speeds (from 1X to 10X). A second kind of CD-RW disc had to be developed specifically for high-speed operation (4X to 10X).