Disclaimer: This is a biased preference. Please give the unit a test run before making a purchase.
The Sennheiser Single Driver IEM has a V-shaped sound signature. The driver is housed in amorphous metal that was 3D printed. You get three pairs of silicone and foam ear tips (S, M, and L) in the box. You get two cables, one with a 3.5mm termination and one with a 4.4mm termination.
I heard enough sub-bass rumble with a decent thump, and the bass is warm but not boomy. The highs are clean with decent air and least sibilance, but for those who are treble sensitive, they can be sparkly or harsh on some tracks.
The decay of the bass is clean and does not bleed into the mids. If you like V-shaped tunes, the mids are laid back and not in your face, which may be beneficial for long music sessions. The holographic sound stage of the IE600 impressed me greatly.
The review is based on Qobuz/AM as a source via laptop onto iFi's Gryphon (using GTO filter) at +61db volume. Please keep in mind that I did not use stock tips, but rather the AZLA Sedna Light ear tips.
Tracks used for this review:
1. 4ware by Deadmau5
2. Rockstar by Post Malone
3. Thriller by Michael Jackson
4. 295 by Sidhu Moose Wala
5. Usure Poyene by A.R. Rahman & Karthik
6. Pathala Pathala by Kamal Haasan & Anirudh Ravichander
What could have been better?
1. The cable quality, which is prone to impressions even with minimal force applied for long periods of time.
2. The stock tips, at least for me, were not a good fit. Although the IE600 sits comfortably and does not feel heavy during extended sessions.