The new Dual Driver Earphones by Xiaomi are an innovative design, as it is one on the first implementations of a piezoelectric speaker in earphones, along with a similarly-designed model by Lenovo. Despite the exciting specs, these earphones reveal nothing new in terms of sound quality. The piezoelectric speaker doesn't seem to be a decent enough alternative to a high-quality dynamic driver or a balanced armature, thus I can't see the purpose of this product, considering its uncompetitive price.
Along with the mediocre sound signature consisting of a non-existent sub-bass, boomy mid-bass and generally nasal vocals, these earphones are also cheaply built and designed. They are, however, quite comfortable, especially if you don't like shoving in-ears into your ear canals, and prefer something less intrusive, but I'm pretty sure that there are better alternatives even for those people.
Good sound quality, specifically for audiobooks or casual listening.
Quite interesting detail in the treble in certain compositions.
A rare use of a piezoelectric speaker in earphones. Thumbs up for innovation.
Exaggerated lower-mids result in a tubby/nasal vocals.
Bloated mid-bass causes boomy percussions.
Complete lack of sub-bass.
Ridiculous build quality and use of materials, for the price.
Although this kind of design provides no seal, these semi-in-ears are actually quite comfortable and easy to wear. The way they sound is very fit-sensitive, so if you can't get the intended sound signature, consider getting foam ear pads separately, as none are included with these earphones.
Lows / Bass
When it comes to sub-bass, it's non-existent. As to the mid-bass, it's exaggerated and bloated, makes every hit of a snare drum almost painful to listen to. Basslines and instruments like the cello sound muddy and fatiguing.
Mids / Vocals
For audiobooks, talk shows and such, the mids are nice. Nothing extraordinary, but clear and listenable nontheless. For music, however, the lower-mids are overblown and nasal, especially for folk music, and if violins are involved, that's almost painful. Tonally, vocals sound a bit off-tone and harsh, even though not upfront, and have a unnaturally low pitch.
Highs / Treble
The highs are quite delicate, considering that these ear semi-in-ears. The piezoelectric speakers give instruments some interesting tonality and even some microdetail, and I can see the potential. However, the whole treble range is underemphasized and overwhlemed by the mid-bass/lower-mids.