My honest opinion
Well, I buy my Hidizs MS1 Mermaid on 2020, MS1 Mermaid soundsignature is almost met my expectation, It had good bass, a bit forward and sweet vocal, and the treble is not really sparkling too July 2023, I decided to buy Hidizs MD4 and that a worth upgrade, I got surprised that MD4 is had very good, deep and punchy bass, even MD4 use 4 Balance Armature configuration, MD4 bass had same quantity and quality like Dynamic Driver bass I got good quality product, my MS1 Mermaid still on good condition, almost no scratch and work normally even I already own MS1 Mermaid for 3 years