I found W4 midrange far to forward, perhaps more than a Shure and also found it unlistenable /fatiguing at louder volumes. Definitely was not for me. W3 is nothing like that. W3 has the smoothest, most detailed treble I have ever head in a universal. It has an uncanny way of producing and an extremely high level of detail while still retaining an underlying warmth making it very easy on the ears.
Not sure why but a few have had fit issues with the short nozzle of W3 creating some siblance but most find it a very easy fit.
I almost forgot how many years of R&D went into making the W3. It was truly groundbreaking. Found this review reminding me of why I like this IEM so much. Scroll down just a tad to Flavios' excellent review. I agree 100%.
(sorry to 'jack the thread, just wanted to clarify about W3) Carry on...