Stage and Resolution:
The First thing what we noticed when we tried them, how great deep they go and how wide the stage of the Quad is. In comparison with the Triple, the Quad is a bit better and you can hear through better. Even though there are BA Driver, you can still use a normal smartphone to drive them, but who wants to get the full experience should get a high-res-player like the FiiO X3.
Bass:
The Bass is one of the Highlights of the Quad, because it is very deep and has a nice mid-bass hump, which is perfectly tuned. Even though the In-Ear Headphone is pretty bassy, the bass has the right amount of body/fullness and doesnt bleed into other frequencies. The Bass has a high impact, which causes to make bassy tracks an artwork for your ears. The Bass sounds very full bodied, without going over borders to be too bassy.
Mids:
The Mids are present and still dont get lost because of the bass emphasis. Due to this the vocals and singers are well presented, exactly how they should be. BA-like the music is played precise and fast. Instruments are well seperated from each other and have a very good resolution. Voices are very near to the head, so you get the feeling you are in front of the stage. The Mids are all in all sound very real and clean.
Highs:
Exactly like the bass, the highs are also a little bit raised, but not as strong. They have a good brilliance and are in the superhigh frequency area very pleasing and full, which might due to the extra BA-Driver which is only for these made. Whats instantly noticeable is, there arent any sharp peaks, which tend to get sibilant. Thanks to the high resolution, the peaks are crystal clear
(C) www.inearkopfhoerer-tests.de/testberichte/1more-quad-driver-in-ear-kopfhoerer-im-test/