The Vortex really is a fantastic little IEM, quite underrated. I can contribute my impressions as well. I recently spent several weeks with it almost exclusively (though after not listening to it for a long time as well) so all it took was a quick listen to confirm what I thought.
Vortex is brighter; has more overt lower treble energy. Quattro dials it down a little in comparison. It is still very much there, just potentially less fatiguing to those who may be sensitive to it (though I’m not).
Quattro has much more air and upper treble that contributes to a larger soundstage and more positional cues.
Quattro is also a big step up in resolution. Not that Vortex lacks it, only that Quattro is more resolving and textured and contains much more fine grained information.
Compared to Vortex, Quattro tilts towards the lower mids. Vocals and instruments have greater note weight as well as sonorority.
Vortex’s bass is textured, detailed and controlled and Quattro simply improves on that and brings it deeper into the sub bass.
I clearly remember, when it was new, how Vortex’s bass nailed this track effortlessly right from the get go. Straight out of the box, I listened to this and wondered if Quattro’s bass drivers didn’t quite have the definition to be convincing. Then I revisited it at some point past the 50-hour mark and there was no denying it this time - the Quattro just nailed the timbre.
Which brings me to this:
Ikr? That was me listening to Quattro right out of the box.
Also me, after 100 hours: holy schiiit, burn in is real…