I vividly remember having a nagging sense of regret when I sold these almost a year ago. I did it out of curiosity to try other phones more than any specific dissatisfaction with the 8400. Obviously it's been a very long time since I've heard them.. but to my ears, their sound was all too impressive to simply forget.
What I do remember quite well was a sound that blended neutrality & naturality exceedingly well, a phone that had immense detail retrieval, and a phone that portrayed a
gorgeous treble response. The general sound reminded me of what a "more robust" RE0 would sound like. The 8400 had an excellent, tight bass response with a surprising punch. The mids were very clear & delicate, possessing excellent timbre.. while the show-stealing treble had an uncanny blend of crispiness, air, clarity, cleanliness,smoothness, and sparkle. Despite all these superlatives, the treble was not excessively enhanced or boosted to give the perception of artificially enhanced detail retrieval. I remember them having a mesmerizing tinge of 'ethereal' warmth at the edges of notes that provided a soft smooth, liquid touch to the neutrality & incredible resolving ability. I also remember them "opening up" to a distinguishable amount after approx 50 hours of use. The other thing I remember was they had a surprisingly dynamic sound (soundstage depth). For such a neutral, monitor-leaning sound.. notes had excellent weight and dimensionality.
After selling the 8400, I had the chance to audition (and/or own) many other fine universal/custom IEMs, reference grade, full-sized phones.. and various amps/DACs. Through all that.. the desire to re-purchase an 8400 (at some point) never went away. I was wowed beyond belief at the gear I heard subsequent to owning the 8400.. but the 8400 always held a special place due to their clear clean, balanced sound. My phone/gear collection had also swollen since owning the 8400. I've slowly trimmed it back to something more manageable (after all, we all only have two ears). I'm at a point now that (with a couple of customs coming down the pipe, too) I find myself very satisfied with the quality of sound my phones/gear delivers. Despite having the HE-500.. it felt as if my collection was missing
something.. what could it be?
So with that, I re-ordered the 8400 a couple of days ago.. and it should arrive later today. I can't wait to hear these beautiful phones (again). I look forward to A/Bing them with the GR07 MKII, HE-500, RE272, and the Heir 4.A (that's soon to arrive). Those seem to be the closest siblings to the 8400 in terms of sound signature & technicalities.