Headphone Reviews

Properly Preparing of Comply Tips for Insertion
Comply tips have two parts: the outer foam; and a stiffer inner tube of plastic that slides over the nozzle of the earphone. The rounded end of the foam extends further than the inner tube. When squishing the foam between your fingers prior to insertion, if you simply roll the tip between your fingers the foam remains longer than the tube. I think this extra foam at the tip can push against the side of your ear canal at the bend and may partially or completely block the end of the tube from which sound emits. This will muffle the sound.

On the other hand, if you prepare the tip by pressing the foam rearward as you compress it, you can make the inner tube the most forward part as it is inserted, making it far less likely to close off as it hits the bend in your ear canal.

I think a video will make this clear:

As an alternative, some people use a razor blade to cut off the end of the foam at the tip. Others will install the tip backwards as the foam and inner plastic of the tube are the same length at the back. These methods probably work fine, but I've simply not found the need if you prepare the tip as shown in the video.

Cleaning Comply Tips
Because of their tacky nature, Comply tips pick up dirt and ear wax rather easily. The best way to have clean tips is to clean you ears regularly, and have clean hands when preparing the tips for use. None the less, the tips will eventually get dirty.

The Comply tips are a very special material and can easily be damaged (disintegrated in some cases) if alcohol, mineral spirits, or other volatile chemicals are used for cleaning. Comply recommends that you simply dampen a cloth with warm water and wipe them down. Then leave the tip to dry overnight. If you soak the tips in water, some of the chemicals in the material will leach out and the tips may degrade more quickly.

Summary
I've found the Comply tips to have very little effect on the sound quality of my IEMs, which is born out in the measurements made. I've also found them to provide excellent isolation, though I didn't do measurements to confirm.

The comfort provided by Comply tips is simply extraordinary. In every case I've tried they are a significant improvement over the stock tips that come with the earphones. Additionally, the security of fit in my ears was much better than stock silicon tips.

Comply tips are about double the price of stock replacement tips, but the improved comfort and fit make them a no-brainer for me. Highly recommended!

Resources
Comply web site.
Head-Fi Comply Tip review and another.