By bassy I mean this is one of the few iems in my collection that might unseat the original brass-ringed KZ ZS1 as my preferred guilty pleasure bass cannon. After listening for almost five hours straight last night I found the bass bleed is controlled and any overshadowing mitigated by a raise in the lower mids. Male vocals seem to be unaffected by all that bass though the upper mids are a bit hit or miss. Some female vocalists stand out, others are too recessed. It really varies song to song. I spent almost all my time listening to electronic tracks for which I consider them near perfect. Warm, lots of bass, clear mid-range, treble that rolls off slowly but keeps the energy and avoids fatigue, big sound stage with lots of layers and good separation. There is an abundance of mid-bass similar to the RT-1, but the mid-/sub-bass balance is better with improved extension and more sub-bass emphasis. You really feel the low notes as a result.
As a side note, the nozzles are open with just a circle of foam stuffed inside acting as a filter. Take that out and they balance out a bit with lessened bass and more treble/mids. People that like to mod should enjoy these, especially since the all-metal housings are just screwed together and easily disassembled.
Stock, these sound like they'd be right at home in a budget bass head collection. If you're looking for neutral...nooooope. Look elsewhere.