Not entirely and I don't need to, I've found a fantastic benefit for me personally about having an inner voice or subvocalising. My reading speed has increased with Photoreading anyway. I actually 'slow myself down' to read a novel in about 2 hours to let it unfold like a good movie instead of spending something like 10 hours on it as I did in the past.

Superreading and dipping you find you drop subvocalisation because you are going too fast. Rapid reading I still occasionaly subvocalise passages or words here and there. I notice on the whole that familiar words get dropped and words that are more important to the significance of the book I subvocalise. I find this seems to help me with my comprehension and memory of significant points in the text.
In any case there is no need to worry about subvocalising just learning the Photoreading System will help you to improve your reading and comprehension speeds. You may still subvocalise and that will be ok because that's how it works for you. 
Alex