The QT3 is supposedly an upgrade to the already highly regarded QT2. In reality, although the QT3 are excellent earphones, I can hardly call them an upgrade. You see... they suffer from the KZ ZS6 syndrome - excellent sound quality but with unforgivingly eardrum-piercing treble.
Other than the exaggerated highs, the QT3 are essentially identical to QT2 when it comes to sound quality, from the lower-end up to the upper-mids. But all in all, after spending a while with QT3, the QT2 are the ones that seem to be an upgrade over QT3, not the other way around, thanks to their milder and more natural-sounding treble.
The QT3 are great, but for their price? I'm not so sure.
The shape and fit are almost identical to that of KZ ZS6. I could wear these earphones comfortably for hours, but just like with ZS6, the QT3 might cause pressure on the ear canals for some people because of the way the nozzles are shaped. The fit is identical to QT2 in every aspect.
Lows / Bass
Super-extended with a beefy sub-bass that makes every bass-centric composition as enjoyable as it gets. The mid-bass is very clean, controlled and lacks any distortions, and is responsible for the naturally warm midrange. The lows mainly focus on sub-bass, hence the upper-bass/lower-mids are very clean and never sound bloated or muddy. I'm extremely pleased!
Mids / Vocals
The mids are almost identical to those of QT2, quality-wise, and I suspect that we're dealing with identical dynamic drivers, probably even identical BAs. However, given the overemphasized treble resulted by the additional BA inside the nozzle, the upper-mids were affected, and instances of sibilance and pierce are extremely common. It's really a shame, because they sound really clear and crisp, and only an equalizer can save you from hearing damage.
Highs / Treble
Super detailed, but also super sharp. Piercing upper-highs cause uncomfortable listening experience with about any high-quality track you throw at them. Admittedly, you can mitigate the issue by using an equalizer, but that wouldn't be fair to appraise earphones by what an equalizer can do. Despite all that, I'll say that the treble is extremely detailed and crystal-clear, and that should be upvoted at the very least, but for their price, I expected a better-thought-out tuning.