[Spyro]

It is my understanding that a boost in the mid bass tends to "cloud" the midrange up a little.  I think many have spoken up about the W4 lower mid boost doing this very thing.  But the W3 has a significant mid bass hump but has exceptional clarity across the entire spectrum.  I wondered with such a large mid-bass boost why the W3 wasn't cloudy sounding as well so I asked Westone this exact question and asked my inquiry be directed to an engineer type person.
 
ANSWER:
 
 As far as the W3 and W4 goes, keep in mind that doing A-B comparisons are subjective, how you perceive one may be different than how someone else perceives it.  Neither one has a mid- bass hump built into the configuration.  Both are designed to be as neutral as possible, the W4 being the most neutral universal headphone we offer. 
 
 
I LOVE my W3....but "neutral as possible"??    Did they miss??  LOL!

 

[Zalithian]

I agree, but I think a lot of people reported the W3 sounded quite neutral with custom tips. I know they were definitely not neutral when I had them (2 pairs) but yeah.. lol. I thought the W3 was specifically a 'consumer oriented' IEM?

 

[Spyro]

W3 is a very unique universal in that it allows BIG bass and exceptional clarity to co-exist.

 

[KimChee]

The W3 has decent soundstage depth, which helps it from sounding congested.  There is a lot of bass, midbass and a lot of bass impact.

 

[Spyro]

  The W3 has decent soundstage depth, which helps it from sounding congested. 

Yes, that's the other thing.  There is like a a reverb effect or depth effect that is more akin to headphones.  Really spacious sounding.
 
A little finicky with tip selection but if you like a heavy sound, it's tough to beat.  You can also make the midrange sound much more in the forefront depending on tip selection.