First 24 hour impression of the spring.
TLDR:
Solid vocal centric IEM with a fast tight bass with above average detail retrieval at the expense of “splashy cymbal” syndrome.
Excels in: Pop(especially female), Slower Tracks.
Weaknesses: Metal (in general) particularly Progressive Metal.
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Source: Tempotech HD Pro (hidisz s8) and Shanling M0. Nothing fancy, cleaner on the HD Pro than the Shanling.
Ear Tips: Went back and forth between various tips eventually settled for foams (and I usually hate foams due to the dirt it accumulates). Stock tips, varying degrees of fun/usefulness, I like the white ones with black stems the best but YMMV. Tried the Reverse KZ Starlines as it usually gives me the best seal but it made the peacock sound more “V” therefore making the splashy syndrome worse.
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Bass: Very Good, Prominent, Fast and controlled without muddying the bass. Very consistent regardless of genres and can hold up to faster genres. Lacking in extension as you dont get the same feeling in Hans Zimmer - 2049 compared to sub-bass focused IEMs.
Mids: I echo the sentiment of many other reviewers that the Mids are done well for vocals and for horns. Vocals feel rich and buttery while horns never get shouty. There is a feeling of “non-cohesion” between the bass and mids transition where lower register of the guitar doesnt seem as “snappy” compared to higher mids section. [The classic Stevie Ray Vaughn shuffle is a victim of this, it sounds a little anemic/woolly]
Treble: I have issue with the treble, they REALLY suffer from the splashy cymbal syndrome on faster tracks. You get good detail retrieval of course, but it really is a nuisance that can cause fatigue really quickly.Not ultra resolving (compared to etymotics ER2SE) but it is decent.
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Pop Tracks Tested:
Aimer - Tone -> As a singer that has that airiness quality in the voice, the spring captures it well. At times it could abit sibilant if she stretches her range to higher notes.
Michael Bolton - Close to you: WOW, despite the fact many instruments are technically competing in the midrange (Flute, Trumpets, Piano, Strings), the horn and the piano sounds fantastic here. Not to mention Michael’s slight raspy voice sounds very smooth here.
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Metal Tracks Tested:
Low Res/Thrash:
Slayer - Raining Blood/South of Heaven -> As lower resolution test tracks, the splashy cymbal syndrome is not as prominent here. Araya’s voice is well balanced, about the same emphasis as King’s guitar work.
Melodic Death:
The Black Dahlia Murder - Verminous/Catacomb Hectacomb. Splashy cymbals are not prominent on Catacomb Hectacomb versus Verminous as cymbals seem to be a bit further back. Bass, Kick Drums are tight and punchy but extension doesn’t go as low. (1:08 on Verminous you can hear the riff but its being drowned out by the floor tom which does not happen on IEMs with more bass extension [I.e. MH755]). Vocals sound better on lower volume as the splashy cymbals not that prominent
Progressive:
Between the Buried and Me - Selkies: Endless Obsession. Like most progressive metal songs, the aggressive metal portion suffers from splashy cymbal portion, but once it reaches the beautiful solo portion you can really test the detail retrieval as the song fades out (you can hear the tapping of the china on the last 8 seconds). Do note : upper frets in the solo gets drowned out by cymbals which was very disappointing.
Thank You Scientist - Party All the Time/FXMLDR. As a band that uses horns in their Prog tracks I can say they hold up extremely well. No shouty upper mids and they gel VERY Well. On 2:10 when you hear all the instruments playing together it never becomes muddy or fighting for your attention.
As a Metalhead, the spring is not my go to IEM. Hell I would even pick up the blons 03 despite its midbass bloat and slow bass recovery because the sound of the splashy cymbals is enough to steer me away.
For everything else that is not metal, this IEM is VERY Good. I was very impressed by how good horns sound on this IEM. I definitely need to do more testing on Genre’s outside of Pop and Metal and also test the fabled burn in effect that chinese reviewers have.
I find them fine treble wise but that’s coming from old ears lol…Nice review btw 
