A lots of X3 owners are not very happy about the stock tips, and many different types of tips have been used to get X3 a better fit. One of the problem of using custom tip is you changed the sound characteristic when you used a type of different tips. Personally I like the sound of the original tips, but it is harder and often hurt my ear after a prolong time of usage. To solve this problem, I changed my stock tips to a softer AT tips (ER-CK5M). However, these tips have less bass and kind of loose (in term, less isolation). To solve the loose problem, I have been using SONGsanmanwah's original idea of
pushing the silicon as far as it goes (pass the holding 'ditch' and getting the nozzle closer to my ear). This, however, doesn't change the fact that it has less bass.
One of the possible solution of my problem is to get an UE bi-flange, but as a DIY'er I prefer to improve it using what I already have instead of buying another pair of new tips. Here is my solution to the problem: The double layer tips - a simple way to get the effect of bi-flanges with what I (and probably most of you) have on hand.
Most of us who own CX300/EP630 (or any similar 'phone) will have more than a pair of same/different sized tips. Push one tip into the nozzle as far as you can, than use a second one to fit the original 'holding ditch' - and we have a homemade bi-flanges. You will need 2 pair of tips to finish this mod, but it is worth it. You'll get better fit, bass is better than single tip, the nozzle is place far enough to reveal more detail (the original single-tip-pushing-back has less detail), and you get more isolation. The best part is, you can use left-over tips to do this (save on time and money). Enjoy it