As some of you might recall the RE0s got quite a good review back when they were launched. Back then competition in the sub $100 market was scarce. That is not the situation today since a lot of new companies focus on brining affordable in-ears to the market. With the RE-ZERO's launch price of $99 they are situated in a highly competitive price tier.
The ZEROs are basically a set of RE0s painted gun metal gray and feature a newer driver. The new driver is more efficient than the old and should provide better bass and a clearer treble. Also new for the ZEROs is the balanced termination which means that you can use it with the upcoming balanced amplifiers from Head-Direct and other brands. Right now there are no portable balanced amplifiers besides the RSA Protector, but that is sure to change within a month or two. Balanced operation should help in terms of sonic performance because such a design is less affected by the very frequency dependable load of an in-ear driver. There will be an update to this review once we have a capable amplifier in our hands.
Detail wise the RE-ZEROs are, not surprisingly, better than the RE0s but not by much. What is especially noticeable with the RE-ZEROs is the improved treble response over the RE0s. The treble is more lively and extends a bit further. Bass wise the ZEROs have a touch more, but are still not bass monsters by any stretch of imagination.
The midrange seems slightly less colored and imaging is a bit better as well, but again no ground breaking difference between the two. Perhaps in a balanced setup differences will be bigger.
Long story short if you like the RE0s you might find the ZEROs to your liking. Beware they do have a slightly more emphasized high end response and that means that they are a little more sibilant than the original RE0s from Head-Direct. The high end can be tamed somewhat by using either foam tips or one of the thick bi-flanges that Head-Direct produce, however, the fit is much more tricky to get right with the tough silicone tips than with the usual flimsy stock single flange tips. You could go all out an gut a set of Shure Olives but that takes a bit of time and is not the most durable solution out there.