Here is my short - noob review. Headphones I know, H25, 59x acutally using it, BeyerD Custom Studio which where treble cans and extremely gimmicky, Neumann NDH20 best ever, P1 gave me murder head ache and Starfield which are the best IEM that do not fit me at all without pushing my jaw down.
TL;DR down below and sorry for the wall xD
I mainly use Spotify and some FLAC. First I listen to L3 custom. Aftert all songs I added the NDH20 thoughts. I mainly listen to Japanese music. PassCode, Tokyo City Pop genre, some retro wave, metal and rock. I also like blues.
The L3 custom do not fit me. The part going into my ear is not big enough to seal at all. The bluetooth module by FiiO - 2 Pin is awful with apple aac and destroys treble with a roll off and the bass gets boosted which I did not really notice on flat - harman frequencie curve - and is okay with a Q5S.
It actually can be the Fiio 2 pin - I cant ever learn the name at all
The review only includes test with the FiiO Q5s running single ended with Toslink from my Asus Ryzen 570 e motherboard with has deap neutralish bass, GREAT treble and normal mids.
The Bass on all songs is tooooo powerful and like a wall that can show texture and blocks mids and can be louder than the treble. Mids seem to fall short due to being V shaped. THIS is actually compared to starfields which I returned as you might have guessed, kilometers worse. L3 loose.
I test my L3 looking 45° down to get the seal. Highs are reflecting and peak in a dirty way. I played music around 5 hours and additional used the nintendo switch to play pink noise on a reasonable volume.
Bring you happyness - kolme : bassy as intended but L3 has too much. Treble dies from getting hammered by bass. Mids are less I do not know if it is just a different presentation compared to NDH20.
ROMANCESECT - zenbukiminoseida. : bass + aparrently high treble and all mids are dead. I can not hear the E-Guitar but the electronic clapping sound can be heard. Singing seems to be crisp but every other mids dies. treble rings badly, even when being in the right position with my head and pushing gently. NDH20 has all sounds at the same volume except singing and high hats being more pronounced on NDH20. No peaks but sparkle but none on L3.
Sayonara Flashback - CY8ER - treble gets cut off and rings. The whole song is present.
東京ラットシティ - CY8ER - the Japenese string instrument peaks and after the short intro gets drowned out by the bass volume. Oh this Japanese instrument! NDH20 can produce these frequencies well. Singing is louder around 10-15%. Some air is in the song but also bloated. Idol music can be loud and full but head worse. I guess paying 500€ incl. tax is still a 4 times increase in performance.
Futsu No Nichijo - Gang Parade - kinda sounds okay. Bass the same story. High hats sounds okay. I could imagine the sound in real life. The voices of the female Idol group sound mostly fine except again the highest voices get cut off and ring even with bass fighting agains that. NDH20 - bass more in background. Voices extend to their best. High notes are louder…
Ariba - Little Big - Russian group sounds good. The members have a great voice. Here I notice the Starfield had a subwoofer feel to the bass like in James Bond trailers / films but the general story is the bass is a wall with L3 custom, darker than 59x and Neumann NDH20 may be dark but it is always telling me it presents me all the bass how it was mixed. NDH20: THIS is a sound WITH a LOT of air and space. It has so much great parts. Mixed very well for my taste. Everything is the same volume with dynamics no compression to 1 volume. Is not at the max volume of the audio format.
Feeling Good - Nina Simone - One of my top 5 songs of all time. Thank You EA for publishing THE SABOTEUR on PC, PS3 and 360. Best EA game btw about WW2 and revenge. High orchestra instruments are not clear. I can not tell what instrument it is but the main instrument, I am bad with any instruments , maybe tuba is one of the first instruments I’ve heard that is clear. NDH20: the pong sound of xylophone was unaudiable before not I can.
I Like It - Cardi B … - Bass sounds nice, Piano can not easily heard, highs are clear. NDH20: I hear the piano but it is meant to be quieter. The bass hits hard.
Umi Ni Naritai - Akiko Ikuina sounds clear because 99% of Tokyo City Pop is mastered to have no loudness war in mind or at least all songs I know have dynamic changes between loud and quieter sounds / instruments.
Personal Jesus - Johnny Cash - Everything is clear but the higher notes of his guitar are recessed.
Super Radio 1960 - Yoshimi Iwasaki - a lot of sounds are too quiet I think. Bass… but recessed frequencies so it is not only the bass. NDH20: Bass, tuba or similar, drums, quiet piano are well recognizable.
Still Sane - Lorde - All songs only have left and right channel movement. There is no 3D audio happening, never. I could not try gaming because I would miss out on ambient bass etc.
Flac music and mp3s - Medal of Honor Allied Assault soundtrack has constant peaks which never happened on any headphone and IEM . P1 included!
Fleeing the Catacombs - The recording has individual volumes for all instruments. Some are also recessed.
TL;DR : Mids -> vocals are always clear but often peak because the driver can not hit the freq.
Treble is reflecting even when inserted and bass is used to lower the awful sounds.
Bass is too much of a wall and some texture shows sometimes but the speed is also not fast enough compared to the A+ Starfield for film fans.
All songs listed
I hope I was not too bad at writing because I have no clue where to look for others. I always tell people buy 58x or Sennheiser HD300pro to get started and then decide what flavour they want.
Edit:
New infos to L3
Firstly the FiiO UTWS1 are the worst thing I ever heard with AAC. Actually the UTWS1 used on my ryzen 3 PC with a Asus 570, except the non working volume, sounds awful too. Do not buy an UTWS1 at all. It is a waste of time. Additionally I always use bad audio devices for at least 2 weeks. I week done and additionally not used it for like 3 days and strangely my ears are different now, swollen or whatever and it sounds better. Mids somehow are not 2 cm out of my ear (0,787402 inches).
The UTWS1 also does not work with custom IEMs which I directly noticed but also the seal works today very okay (do not want to give ThieAudio credit for my right ear being bigger than the left when talking about comply foam).
@PapaEmeritus The roll off is awful. The L3 is the HD800 no joke with the wrong audio.
Bring You Happyness from the spotify list still has strange unnatural sparkle or and peaks but bass IDK why is now less than HD59x, of cource less detailed than NDH20 but now actually neutral. I did not use it at all for 3 days and use it for 30 min to and back from work. It was awful. L3 custom still vibrates with at least the fiio bluethooth paper weights. Now finally retrying L3 on my PC via Toslink Q5S and also sound finally right. I know burnin is a thing but never had 2 changes in sound. Bass needs most burnin, mids dont but without a seal of 85%+ is feels like some BA is blasting outside your head and even your ear. Volume can not fix it and treble hurts when not working properly.
“Romancesect” has bass but it is flat. Retrowave and Jazz are the best genres on these by far “Custom Only” not the normal ones. Before the X moment where the fit and sound randomly changed to a C- to a C+ or 2-. The seperation was non existing. Trumpets still glow like rusty rails in wood.
“Still Sane” by Lorde is unlistenable and treble reflects.
Run The Jewels now works but treble still peaks. Compared to the 2016 Audio Technica E70. The resolution is similar but better. Bass has resolution and is not just 1 bass note with random bass inserted into songs and games which do not even have bass. E70 added tank engine bass where none was in Hell Let Loose beta. String instruments sound.
“Broken Silver Androids” - Maximum Love sounds great now. The only real sparkle if even possible is in Retro Wave. Mids and Highs are most likely on my set not doing sparkle except here.
“Opr” - Gessaffelstein has cut-off treble but I also notice the ONLY flaw when the magic of real inserted L3 customs happen - the TREBLE SUCKS. E70 can do it smoother and E70 directly go on mute when you slightly pull it out. The 3 BA drivers can not do any sounds with free air circulation.
TL;DR this IEM may be good, but the dac & amp and audio source will make it a deal breaker for people on a tighter buget. Bass works maybe for today 9:37pm and go again with my ears. Mids sound now. Medal of Honor soundtrack by Michael Giacchino sounds a bit dull but does not peak. So all genres work when there is no real peaky highs, hardbass (not the generic meme hardbass but original hardbass so no DJ Blyjatman), no Gesaffelstein-like music.