Okay this is just ridiculous. I refuse to believe that I just paid $99 for these. I've had these things in my ears for the last "I don't know how many" hours, and I can't find a legit reason to take them out. THESE ARE NOT $99 IEM's! They're IMO on the caliber of $500+ IEM's, but somehow made available miraculously for the money-starved audiophiles. Do not let the price fool you! I am nominating the RE-400 for the "head-fi all-time best bang for the buck" award.
I have never heard better sounding treble! That's saying a lot since I've heard both the RE0 and the ER4S, which are both touted for their treble performance. The RE-400's treble is so effortless. Smooth. Realistic. Detailed. Shows no signs of dips or spikes. I have never heard better sounding bass! This is coming from having heard the GR07, touted for its supposedly some-of-the-best bass quality. The RE-400 may or may not have the GR07's control at the lowest lows (I don't really know because I haven't tested this, since I don't listen to genres where sub-bass is of any priority), but what it definitely does have better than the GR07 is slightly more accurate decay. The GR07, to my ears, is slightly bloated. The RE-400, after burn-in, shows its bass prowess in my most bass-demanding track that I keep around solely for testing bass quality: Infected Mushroom - Heavyweight. Make no mistake - the RE-400 can rumble when the track calls for it... and can do so at high volume without at trace of clipping! Its attack is also no slouch here, easily competing with the GR07 in this regard. These are mesmerizing in the lows, and deathly seductive in the mids and highs.
Soundstage... Sure the ER4S, I must admit, has really pathetic soundstage for a $300 IEM... but I simply don't recall an IEM that does soundstage as convincingly as the RE-400. I don't recall the GR07 having the 3D, layered presentation that RE-400 renders. I also don't recall the GR07 producing an out-of-head feel like the RE-400 does. Soundstage on the RE-400 is big, life-like, yet beautifully intimate. You're right there with the singer, but he/she isn't in your head.
Treble... oh wait - didn't I already write about this? I think I might need to control my enthusiasm... Alright, if you bump up the 8kHz-20kHz range by 2-4 dB with equalization, you'll definitely enjoy the bit of extra brightness. Without this enhancement, the RE-400 may be viewed as ever so slightly relaxed in treble. With the bump, they still have less treble energy than the ER4S, which to me has just a bit too much sometimes. Both quantity and quality-wise, the RE-400 nailed it.
Midrange?u Gently liqid. Able-bodied, yet not so much so that it sounds like the monstrosity that is the SM3, which literally butchers vocals in a gruesome manner. 99% of my music collection is vocal, so midrange accuracy is very very important to me. Let me repeat, very very very... I do feel like these could use a little nudge in the upper-mids and lower trebs, which with EQ made it possible and vocals more accurate. 9/10 without the equalization, 9.5 with.
Bump up its sub-bass and they will obey effortlessly without clipping.
Ohmygawd, the soundstage!! ... okay, I need to get a grip. Just get these!! Best $100 I've ever spent. Period.