I joined because I thought I had something to say that might be helpful to someone, because I surely could have done with this advice. I went out and bought the 4sl after listening to the 3sl at a recent show here in Japan (some hog on the 4sl and not enough time), loved the 3sl so much and thought the 4sl might have more to offer (my mistake). One week later I went back to Yodobashi (live in Japan) and bought the 3sl. Now I am happy, but have to live with myself for wasting 22,000 yen on the 4sl. My reference IEMs are the SE535s which I enjoy very much, however I was so captivated by how much the 3sl engaged me at the show, I was sure the 4sl would challenge the SE535. Not the case. I am so enthralled by the 3sl that it's my go to above the SE535 this past two weeks. Reason: mid range is so full and detailed and bass is complete, not as detailed as the 4sl, but for my music that's perfect (Floyd, Broken Social Scene, The Cinematic Orchestra). High band on the 3sl is also not as detailed as the 4sl, but much less obvious and tiring. Perfect. What troubled me with the 4sl was a glare across the mid range that annoyed me to distraction. I found relief on string and instrumentals where the 4sl excelled, so much detail in the low and high, but that was it. Vocals on the 4sl made me feel like I was on the second tier at a second rate concert. My thoughts only. If you are considering buying the 4sl,.. AUDITION FIRST! 3sl... I love you... and for that price my wife can have one too.