I must say I was very excited to try these headphones. Finding balanced armature drivers in the budget headphone segment always impresses me; dual drivers do as well – this is the first time I’ve seen both of these qualities in a single pair of headphones and I was intrigued to see how KZ did at fine tuning and balancing the characteristics of these two different drivers.
My first impressions were mediocre; the size of the sound-chamber is quite large and it took me a while to get the tips situated properly.
I next realized that the sensitivity of these IEM’s is quite low and I had to crank up the source to get a reasonable volume level.  This lack of efficiency must be due to having more drivers to push.
Soundstage and High-End:
Once I had the drivers hopping I reached out to feel through the soundstage and again was confronted with a mediocre impression – the soundstage felt reasonably wide but the instruments felt somehow crowded together.  Not the most inspiring, but not the worst.
Looking back over my notes from first impression listening to Alphaville’s ‘Big in Japan’ (BIJ), under ‘high-end’ I scrawled ‘blaringly painful’ and left it at that.  And this really sums up the first and last relevant point regarding these headphones – the treble is just horrible.  Like really awful – grating, distorting, sibilant, whatever adjective could negatively describe this frequency of sound would likely apply here.  This is a deal-breaker and overshadows any other redeeming qualities these headphones might have.  The problem could potentially be helped by aggressively tuning these IEM’s but customers shouldn’t have to correct this level of error.
Like I said, I really wanted to like these headphones and, in the interest of giving them a fair shake, I even burned them in for over 20 hours thinking that perhaps the trebble would be reigned in and join the other registers in some semblance of a coherent sound; I regret to report that it was all for naught.
Mid-Range:
The mid-range sounded quite good on these – I was impressed with the realisting sounding drums on The Doors ‘Texas Radio and the Big Beat’ (WASP).
Bass:
This is certainly the most impressive part of these headphones and rightfully so, the dynamic driver is solely responsible for providing deep accurate bass as the balanced-armature is responsible for making you grit your teeth.
Dr. Octagon’s ‘Earth People’ was suitably punchy and impactful while The Dave Brubeck Quartet’s ‘Three to get Ready’ showed up with remarkably detailed stand-up bass which was incredibly enjoyable to behold.
Conclusion:
There’s a lot to like here but savage high-end mars the whole experience.  These could potentially be salvaged with aggressive eq settings but why bother; check out a single dynamic driver from KZ that blows these away off the shelf – KZ ZS3

The first thing I noticed about the KZ ATE’s is that the ear fit was not great, I had trouble sitting the foam olives in my ears.  This was surprising because I usually prefer Olives to Silicone tips; not in this case!!
The soundstage was unimpressive, it sounded like listening to speakers @ about three feet away.  Sound seperation was not especially noticed or engaging.
High-end:
I noticed a lot of distortion and shrill sounds listening to Change by Blind Melon (BM), although there was a reasonable level of detail.
The electronic sounds of Alphaville’s Big In Japan (BIJ) were flat and retained the shrillness when peaking.
Mid-range:
The mids sounded muddy in BM and BIJ.
The situation improved listening to The Doors WASP – Texas Radio and The Big Beat (WASP).  The recording’s intentional distortion tied in to the sound signature of these IEM’s and provided a better overall experience.
Best midrange for these IEM was found in Dr.Octagon’s Earth People (Dr.Oct) as the less nuanced sound signature and pushing bass seemed to open up the midrange to these urgent hip-hop vocals.
Low-end:
This was the best part of these IEM’s.  They seem well suited to hip-hop and rap and to open up when bass is pushed.
Noise Isolation:
Non-existant due to poor and shifting fit of olive tips
Genres:
Best suited to intentionally distorted recordings of classic rock or punk-rock.
Bass-heavy hip-hop and rap also opens these up to present a better sound
Jazz and subtle or detail-oriented sounds are not suited to these headphones.
Ear Fatigue:
These olives do not like me.
Build-Quality/Design:
Overall decent build but gaps on housing seams are noticable and detract slightly.
Olives are horrible.  Over-ear cabling is uncomfortable and just doesn’t work very well.
This design is generally improved and iterated on the exceptional ZS3’s from KZ
Conclusion:
Sound is okay, better than stock earbuds, but still has glaring issues.  Highe-end is shrill, mids are muddy and tend to dissolve into the lows onall but the most aggressive hip-hop.
The intentional distortion on WASP suited these headphones well.