Hi:
For anything above Holosync Awakening Level 3, according to Centerpointe, you need to have phones with a frequency response of 5Hz - 30KHz, otherwise you will not get the benefit of the binaurals beyond those levels. CRI suggests the Sony MDR-V600, but they are over-the-ear phones (although I find them very comfortable to use). I purchased them when I moved up to Level 4 last year, and going back listening to earlier levels, I kinda wished I had actually purchased them even sooner - the difference in sound quality from ordinary 'phones is substantial.
You might be able to get away with the ep630's for a while, as some people on a different forum seem to be of the opinion that it's just not possible to have tones as low as CRI claims are on holosync and still have them audible. Perhaps, because they are "in-ear", and therefore the tones coming through are much closer to the ear-drum, and not being warped by air between the 'phone and the ear, the one Hz difference in the ep630's may not be an issue.
My own personal perspective on this is, if you're going to put out the money for the holosync program, why take a chance on NOT getting all the benefit you should be getting by using 'phones that don't measure up to the program.
Cheers!
Unis
