Well guys, I have a bunch of other headphones that I listen to and AB on a regular basis, so these are all my impressions of how the Etys and RE-400 compare not only to each other, but also to the other headphones. And I got some great reference cans to compare against - HD650 and HE-500, both of which need no introduction. I find that RE-400 sounds more similar to HD650, while the Etys sound closer to HE-500 in character. HD650 and RE-400 both have that extra rumble that HE-500 and Etys don't have, but at the same time don't sound quite as clean and tight in the lows as the latter two. HD650 does have a big advantage over all of my IEMs in presenting the proper bass impact and power, especially in the sub bass, probably due to its really well executed open back design. I find Etys, both HF5 and ER4, to have very similar bass quality to that of HE-500, although HF5 doesn't have the extension of ER4 and is slightly muddier in comparison. Actually, I think the Etys sound a bit tighter, but roll off earlier in the sub bass than HE-500. Both the high end planars and Etys have exceptionally clean, tight and textured bass that most dynamics, with the exception of the top ones like HD800, just can't match IMO. Actually, HD650 and RE-400 come pretty close and have a sufficiently good bass quality for me. If I only listen to either of the two for a while, I become perfectly happy with their bass quality and forget about the tighter bass of the Etys or HE-500. HD650 edges out RE-400 in bass reproduction because the bass, especially sub bass, is better felt on the full sized can, although bass quality is probably a bit higher on RE-400. In the mids, HD650 beats RE-400 in resolution and timbre, while RE-400 beats HD650 slightly in clarity. Both fall short of the transparency, clarity and realism in the midrange that HE-500 and ER4 are capable of IMO. In turn, HE-500 beats out ER4 in midrange smoothness, while retaining ER4's resolution and transparency, so the former is my midrange reference. In the treble, ER4S reigns supreme over all my other headphones in micro detail definition, but falls short of HE-500's speed IMO. HD650 has more even, more detailed and smoother highs than RE-400, but falls short compared to ER4S and HE-500. Overall, I would rate RE-400 and ER4 compared to my other current cans (those that I still actually use that is) in overall sound reproduction quality in each part of the spectrum as follows: Bass: HE-500 > HD650 > ER4S >= ER4P > PFE >= RE-400 >= HF5; Midrange: HE-500 > ER4S > ER4P >= HD650 > RE-400 >= PFE >= HF5; Treble: HE-500 >= ER4S > HD650 > RE-400 >= ER4P >= HF5 > PFE.