The core is cut from the Westone white triple flanges, cut in length to just below the end of the iem nozzle. I'm terrible at describing sound sigs, but with the larger opening of the 400, IMO, it creates a very neutral sound that maximizes the treble range (to the extent of the W4's capabilities), maintains the Westone mids, and still provides the bass kick that sometimes goes missing with other tips (though I've always been satisfied with it's low end, especially when amplified). I feel that I get the best of the highs because it basically opens the port opening straight to the ear canal, and doesn't require deep insertion to still maintain coherency in the lower mid range to low. It works for me, though I know a lot of people don't find Comply tips very comfortable. The W4 is just a warmer sounding iem, which I generally prefer, but I still wish there was a tiny bit more sparkle in the treble. Then again, I'm an old man and my high end hearing isn't so great anymore! Like so many people have already said, the W4 is not remarkable at any one trait, it just performs solidly top to bottom with all music genres. Of course, that's just my 2 cents worth.
