In the past, I owned a pair of genuine CX500. Now I've got fake CX400s. I was astonished by the fact that the fakes are quite well made. Frankly, apart from sound quality only small gaps between earphone's parts indicate that they are fake. Other differences are noticeable only if you have a genuine pair to compare.
After some time Sennheisser's logos stared to fade.
Whole sound is boomy and bloated, and genuine EP630 blows them out of the water.
Summing up, don't bother risking to buy fake, they are worthless (I bought mine for 5$ and they are not worth more than that)