Ahhhhhh. The newcomer to the space.
So Ziigaat is apparently an OEM that had existed for a long time. They came basically out of nowhere with their new company name and immediately started swinging with the big boys…and they certainly hit the ball. Problem is, the ball went so fast I think it put a hole in the stadium wall…
does this count as a homerun? I don’t know lol, but they certainly made an impression.

INTRO/DISCLAIMER
FYI I am not important or influential enough to be receiving free review stuff from companies. This was purchased as part of a bundle for $20 with another cable. Typically this IEM retails for about $25, you may see some other sales eventually time will tell. This IEM is certainly within the budget range amongst some of the greats and newcomers. chu 2, hola, wan’er, zero(now zero 2 as well), ew100p
just to name a few….I want to be lenient here due to the price range but I have to warn anyone, at least based on my canal shape that any of the others mentioned below will probably be a *safer* (not necessarily *better*) option which I will explain below.

Objective performance/graph

(credit to achoreviews for his graph)

So…looking below I wanted to point out one of the graphs of this new budget contender compared to an iem I thought was interesting. The Nuo has a little more 5khz energy and dips the 6khz “early” treble a bit and then you should notice something…the 9-11khz energy is very prominent, not dissimilar to iems “graphically” like the ie600 or even the edx ultra. Some also complained about sibilance/harshness on the IE600. Are they long lost cousins?…who knows. I’d love to try the 600 if I ever get the chance but it wouldn’t surprise me if the presentation was similar
OVERALL. This graph is a fairly accurate representation of what I hear on the Nuo. Others have shown some driver imbalances, to my ears both sides sound pretty much the same and exhibit the same tonal characteristics.
When performing a sine sweep: Bass went very reasonably deep being audible at low volumes around 25hz. Nothing funky in the mids being very flat and straight up to 3khz. In my own testing, *yes* the 5khz region is slightly boosted in comparison but nothing severe or grating. The 6khz subsequent dip is very tastefully done, no problem here and perception of it has it maybe 2db lower than 5khz(good neutrality!)
…aaaand then here is where the problem begins
starting around 8.5khz going upward to my ears there is quite a big rise in volume. This boost lasts until about 11.5khz and then finally dips again and the sound will cut out at most people’s ears around 15khz(i’m sorry that’s just how human hearing works, no amount of extension will bring back higher frequencies lol)
this approximate 9-11khz region perhaps it is my canal but? this is the problem area(for me). But I’ll get to that below in the subjective impressions.

Bass
The Nuo exhibits a fairly light, almost elegant bass. I would say for a single dynamic driver it is almost *perfect* if such an adjective is ever appropriate. The midbass brings just the right amount of warmth and body to the sound without ever bloating or bleeding into the midrange. Bass lines are quick and incredibly textured for what they are. Subbass rumble exists, but won’t blow your skull out of its head. Bassheads may want more but this nice and very balanced bass, without ever being boring or anemic. excellently done.

midrange

The mids are slightly recessed without ever getting drowned out by bass or (early)treble. There is no shout to speak of. The mids don’t exhibit any thinness to their character, there is no wonky tonality. I can tell that Ziigaat never intended for the mids to be the star of their show but in their own way…they are. They are well textured and layered

treble

Ok…so all things considered at this price point? The treble is still excellent, but here be where ye problem child lies(for me)
Around that 10khz region personally if it’s boosted is grating to my ears. Every vocal along with most instruments and synths in the background exhibit this almost air but not quite upper emphasis which does indeed change the tone and timbre. I’ve noticed recently that a lot of IEMs will specifically dip this region, whether intentionally or due to driver limitations? who knows. But the effect is clear(no pun intended) that this particular brand of sibilance is cut out of the mix and then the 12khz+ air is free to shine(also no pun intended)
Both presentations are unnatural per se but I think I tend to agree with the latter more overall as far as general listening is concerned. The boost in the 9-11khz is simply too much for my ears and can get fatiguing. On the flip side, this does actually lead to quite great texture. In *well recorded* tracks, this treble boost will give grit to the sound and bring texture and detail like nothing else. In badly recorded or just bright tracks, the treble boost can push the sound over the edge and the texture just breaks and falls apart into…treble.
The resolution these bring is nothing short of commendable, i’m sure in most part due to the boost. Others describe the “layering” and I agree. it is good in a vacuum, and for the price? it is stupidly good. Only ding may be if the treble boost ever becomes too much and masks the lower frequencies…that’s no bueno. I haven’t heard that too much but I’m sure it’s possible.

soundstage/imaging

Perfectly fine. I wager these would work well for gaming. Imaging is quite precise, these are good for monitoring. Stage width is quite good and as mentioned previously the directional positioning is more than acceptable. These might even best out the tinhifi elf I recently reviewed. These both have similarities in the staging and imaging.

Conclusion

if this was 10 years ago these things could have had a 500$ price tag(with slightly more ornamentation and accessories to fool people into “looking” expensive) and no one would have bat an eye. I wager it would have actually still picked up a lot of popularity and even have gotten a cult following.
This is a new era though. An era of science and truly great sound for IEMs, so the bar is set very high.

These are a jaw clenching set of IEMs(to my ears). I recently obtained the truthear zero:red and noticed a slight lack of that upper treble emphasis…well now I got it. While the reds dip the 10khz slightly, the ziigaat gives that region in spades and the effect can be a little jarring. The ziigaat nuo is an iem that won’t let you relax. It’s shoving its technicalities and treble all in your grill whether you like it or not. If you ever find yourself finding most iems dull, having no treble sparkle, you run a sine wave sweep and you find that your 9k-11khz energy is sorely lacking. This is the IEM for you and I give it a full FIVE STAR recommendation no frills. If you are sensitive to that region, beware. This is not as safe of an option as the wan’er, hola, or recently zero 2 which are all not going to be as technically proficient but are not ever really fatiguing.
The ziigaat nuo will probably be more immediately impressive than any of the other iems above…or really even iems costing multiple times this price. But it may not be the best choice for a beginner and ultimately would have to refer someone to something like the wan’er or zero 2(if you find the shell ok) despite those being more…generic and having less *character* so to speak

At any price point much less
$25, the build quality shape, size and fit are more than acceptable. These guys at ziigaat know what they’re doing. It’s literally sound alone that is just on the cusp of being great vs being sibilant. If you need a slap in your face and some audible chili peppers in your life? this is the one for you.

Ok…this is gonna be a small review and i’ll briefly talk about each category and the overall conclusion and who I think these IEMs may be for, along with how Tinhifi can do bare minimum things in the future to refine this design and make a real slam dunk for the same/similar price in the future

Let me start out by saying as a preface: these past couple of years for IEMs have NOT BEEN NORMAL. We have seen some INSANELY GOOD releases for very cheap which have absolutely demolished many mainstream and even legendary over ear headphones in terms of frequency response and overall sound quality. in the past, I would have given these a 4.5 star rating based on sound alone, much less for the price….but this is a very competitive market. Kilobuck destroyers are a dime a dozen now
That being said, these are still $15 for a detachable 2 pin cable IEM, below even the ridiculous $20 hype budget segment these days. so let’s get into it

Packaging

Nothing special here. a very vanilla cable(but with a chin sinch! way to go tinhifi!)some very soft squishy and quite frankly terribad ear tips that I completely ignored, a probably not so great preformed earhook, and the IEMs themselves. needless to say Tinhifi spend all their money on the actual iems(which is good!). No nonsense packaging, small box. Good job tinhifi. Hopefully in the future give us better eartips though and maybe a cable similar to something like the chu which is a little thicker, and more pliable. overall not bad

Build

tldr; the c0 elf are built great! they look amazing. Full aluminum construction feels like, so they’re durable but light. No issues here. The one problem I do have is not with the build but with the shape but i’ll get into that later….

Fit/Comfort

Ok so this is probably the first real misstep on the part of tinhifi and probably their most significant one. I have some other bullet iems and I love them…but this is a 10mm driver. The edge around it behind the nozzle is THICC, and it makes it hard to get a good seal or to fit right. Unlike the quarks which are tiny little things, these have a big profile and that huge driver is supposed to stick right in your ear. I didn’t even try to wear cable down I could tell before even playing music it wasn’t fitting right, so I went overear. The cable does not help here either though and it becomes somewhat tedious to wrap the cable over my ear. comfort once it sets right is OK but after about 1.5 hours I got a little fatigued. Even over ear I had to be careful because sometimes I would lose bass and treble clarity and sound would become distant and flat. The fit really hampers this kind of sound signature they’re going for unfortunately, because it’s a good and ambitious one
I think the idea of a less “semi custom” iem like a bullet is fine but in the future i’d recommend against having a big driver configured that way. Perhaps if they still want huge 10-11mm DD they could shape them like those old Panasonic HJE-120 earbuds with the nozzle sticking to the side, that seems to be another successful casual way of wearing iems. Or if they go with a smaller driver they could have a shell shape reminiscent of the shure se215 which would be cool and the market is severely undersaturated with…just ideas. Take note tinhifi. or don’t, i don’t really care other than to advance the market.

Sound

Ahhhh, arguably THE most important part of not the only part that matters to some audio enthusiasts. So how do these sound(or should anyways)? i’ll break it down by lows-highs and then go over technicalities/timbre

bass

this is almost a niche in modern chifi… These hark back to ye old times when most IEMs did not have a dedicated subbass boost, even the ridiculously expensive ones. The C0 Elf are unashamed of being quite neutral in the bass department if not a smidge rolled off in the lower end.
When doing a sine wave sweep they do however go very deep. I started hearing the bass around 28hz(you may hear it lower, i’m not perfect). There was a bit of an odd dip around 42-48hz but it snapped back up past 50hz and was perfectly normal past then. needless to say, what this means in reality is that the bass is soft and never intrusive. It does have extremely good speed and control. These are not for bassheads but should be satisfying enough for most music lovers and they are not as rolled off as most open back over ear headphones

mids

Not bad! good tone and timbre. Note weight is not too thin it has good body to the sound, transients are nice. The tone is very neutral, almost analytical but not “cold” thankfully. The instruments and synths have a lot of separation and basically zero mud or bass bleed here. these are very neutral up to about 3khz so no oddities here. Vocals and synths have a little crisp edge to them but lower frequency grain is kept to a minimum. Things sound how they should(and where they should), there’s no wonkiness here. Acoustic music especially sounds wonderful and the plucks of guitar strings are very satisfying.

treble/detail/resolution

So these lil guys can get a tad bit spicy. I think the treble overall is actually quite balanced, it gets a little accentuated by the presence region around 4kh-7khz. I think the fit/eartips may also have something to do with this as well or may exacerbate the problem of too much treble if you’re not careful. Overall the treble is front stage but not horribly fatiguing or thin. Instruments and vocals sibilants have a satisfying albeit sometimes too harsh(mostly on poorly recorded songs) edge to them.
As for detail and resolution the treble is crisp but does not seem to mask the lower frequencies(thankfully) and so it actually does lead to a sense of a very detailed and analytical presentation.
this is not an overly hyped or exaggerated treble to try and give a false sense of detail. It is overall an appropriate amount that actually does make the sound quite hi res, LAUGHABLY SO for 15$. There is only so much information that can be extracted out of any song, and these do a superb job. The softer bass along with the flat mids and treble presentation really bring out that separation. The decay of the sound is quite fast…the c0 elf(when sealing correctly) will wallop the pants off pretty much any over ear in terms of detail retrieval.

imaging/soundstage

the other coin of technicalities…these are good, very good for an iem. sounds are separated nicely, and they’re decently far away not closed in. I wouldn’t exactly call this a “large” soundstage by any means but probably the largest i’ve heard on any IEM. The sound placement is accurate and almost “fast” weird as that sounds. They appear and disappear like a ninja with great accuracy. No mushiness with the imaging here I’d wager the upper treble really helps bring the full picture together in a coherent way. impressive.

Comparisons

So going almost entirely based off memory

vs moondrop chu
they sound quite similar
even the Chu funny enough has slightly more subbass presence here. the chu has two problems which the tin elf does address though. The elf doesn’t have a “cold” tilt in the lower mids while chu does. Chu also has more 6khz presence which can be heard in the timbre while the tinhifi elf while still having quite a large amount of 6khz ish energy, is not not as much as chu. The c0 elf may be even more detailed than the chu when seated right but they trade blows. the elf and chu are similar in that they have crispy upper treble, the elf might even have a bit more. So if you’re not a fan of upper treble air and sibilants, stay away from both..

vs tangzu wan’er

Wan’er is more of a people pleaser. the tangzu wan’er has more bass, more warmth(little bit) and everything is more upfront and center. They both trade blows when it comes to tone and timbre. C0 is lighter with more sibilants. Wan’er is more “natural” and emphasizes the grain on vocals as opposed to upper treble sibilants like the c0 elf. As an overall well rounded and less fatiguing IEM the wan’er is more versatile but when switching back and forth, the lack of upper treble can make it sound a little dull in comparison.

Conclusion

So I ended up buying these on a whim almost entirely based on their frequency response graph which had intrigued me. They graph very well, betraying their modest price tag and going into the realm of much more expensive sets. The overall lower mids/bass curve is almost identical to past more expensive sets like Blessing 2(OG) or Aria Snow Edition. The upper mids/treble graph very similar to the KATO eerily enough. So…do they sound like they should?

I mean…ideally? when the stars align? …well, maybe? I have no clue. sorry if I burst any bubbles lol

i’ve never heard the KATO or B2 or Aria Snow edition but a graph is a graph and numbers don’t really lie. There’s little surprises as long as the IEMs are actually delivering the sound they’re supposed to and it doesn’t get lost in translation due to bad fit/seal.
…and so that leads me to my biggest caveat! these bullets fit nothing like any of those previously mentioned 3 IEMs. This is a problem because the poor little elf need as much seal as possible to help with their very modest bass presence. When it’s right? i think it’s *juuust* enough to deliver a very satisfying and engaging but clean sound. but they can be finnicky(for me anyways).
know what you’re getting into. For the bog standard average person I would not recommend these and instead suggest saving those few extra dollars to go for any of the insanely good chifi options out there. Hola, 7hz zero, wan’er(I can personally attest to), simgot, etc etc…
These are probably marketed as entry level normie type iems but they’re not that. These are similar to my old etymotic kids ek5 in a sense…the sound signature and fit lead them to be type casted to a very neutral role. If they fit your ears, they should have a place at least if you’ve never heard what an IEM with no bleed and good tuning sounds like.

The c0 elfs were a great experiment. I hope tinhifi is listening because you guys got *so* close to hitting and absolute freaking bullseye. I think 3 things could make something like the elf an absolute banger
1.the very deepest registers of subbass extension like 60hz down to 20hz could be a *smidge* more, to be on par with something like the chu but still not take away from the crisp neutral nature of it. I’m talking like 2db-3db here max. I know the driver can do it, the c0 elf driver is fantastic.
2. the chilled out bass of the elf also means that the upper mids/presence region can probably be relaxed a bit. This would be a similar tuning philosophy to maybe something like the Dark Magician *HINT HINT*. Something that is quite a hole in the market
3. THE MOST IMPORTANT…redesign the shell shape. Bassy iems can get away with a mediocre shell. This style of tuning absolutely cannot. as previously mentioned something like the elf must Squeeze every inch of bass they can through good seal and that will also improve the other aspects of sound

Overall I give these a 3.5 star and it’s a sad 3.5 star because it could be an easy 5 market disruptor and i would like to see if they can improve this design in the future because the intentionality was definitely there.
Design/fit/comfort =2.5 star
Sound=4.25 star
overall: 3.5 star

it was a good effort.

EDIT: after trying some more eartips, I can definitely feel that the seal is actually very good now and some of my original complaints about the sound are toned down. Comfort is much better too. The overall signature is still the same. Bass has been brought up a tad and the etching brilliance of the mid/upper treble has been toned down. When working as intended, this is a very nice sound! However my original description and review is still quite accurate. These will never magically become a bassy, dark, or laid back set no matter what tips, fit, or seal you’re getting(unless you use EQ). I am still keeping my review at 3.5 stars I do believe that’s fair due to the struggle of needing to find proper tips for this particular shape even then, it’s not exactly a safe bet.
but yes if you have the right ear shape and the right set of tips? very good monitor-like but still fun and engaging sound. quite nice!

ok ok...wow. Where do I begin? So much to say...
Preface: I bought every single headphone and iem including this one with my own money. I have been a casual "audiophile" for about 10 years and seeing how the hobby has changed over this period of time, especially recently is just insane. I will only be reviewing the sound(build is fine too, great even)

So the Wan'er...the Tangzu wan'er. How do I begin to describe this thing? Let me start with a graph because this picture is worth 1000 words, certainly in this case

LOOK AT THIS GRAAAAPH


(image thanks to Vortex reviews. He's a good measurer!)

If you're wondering "hey! that looks pretty flat". Well yes, yes it is. The Wan'er has a tuning almost identical to the etymotic reference target, and very similar to their own er2xr(maybe even slightly closer). This sound signature is quite frankly *the* definition of flat since 1990 + added benefit of a mild bass boost to thicken the overall sound and get a nice low end shelf. The Tangzu Wan'er physically looks and measures like a set that hasn't really existed until about 2-3 years ago? There are sets that cost hundreds if not thousands of dollars that objectively have a worse tuning than this. That is not a joke. This is a top 1% IEM. So now the question becomes: Does it sound as good as it looks like it sounds?....
.
...
.........yes

Sound signature:
If there is a single word to describe the signature it is just simply *sound*. The overall tonality of this IEM probably can be described best as neutral with a tinge of warmth and low end. The wan'er tends to take on the characteristics of whatever is playing through it. Your song is shrill? it's shrill-ish. the song is muffled? the wan'er becomes muffled. It is a chameleon of *sound*. As a fair warning, I've never truly experienced hi-fi TOTL IEMS or even headphones or speakers so I cannot comment on those but I will give my impressions compared to gear that I have and use or have used on a daily basis.

Almost every other single headphone or IEM I have has it's own "characteristic". For instance, no matter what plays through the Chu it tends to be a little leaner and lighter in body and bass. The CRA has this glassiness across every note and is thin in its own way too. The moondrop quarks and even my HD650s are neutral-ish? but have this "lovely" tone to them where things are smoothed over just a tad and it creates this soft and very famous Sennheiser "veil". Is it a problem for 99.999% of tracks? no. Does it exist? yes. The wan'er has no such characteristics. The tone is perhaps most similar to quarks/hd650s but still different enough to where it does not exhibit the same lovely tone that the quarks/sennheisers do.

Lows:
Lmao so right off the bat this is where things get hilarious. Graphically speaking this little $20 dollar...device, has a cleaner yet bigger bass shelf than Aria. This is confirmed on many people's squig charts.
Granted, the change is very subtle by like .5dbs and overall I have *not* listened to Aria but it is not out of the stretch of imagination to assume that the overall tuning of the lows is very similar to IEMs like the Aria or maybe the KZ EDA balanced.
Impression wise? No surprise. It sounds like it looks. The bass has authority and slam but also texture and feel. The bass never overstays its welcome, never really intrudes despite how decently loud it can get to my ears. Idk if this can be classified as "detail" per se but the bass never bleeds and a distinct note can always be heard. Other than Chu this is probably the cleanest bass I've ever heard. It also has much more rumble than Chu and overall can hear more of that low end in terms of quantity. Very very well done.

Mids:
This goes back to overall tonality really. The wan'er's mids are, correct. . When I listened to crinacle's review of Chu I actually disagreed overall. I'm no hi-fi expert but IEM's like Chu and CRA sound like detail MONSTERS yet have a brighter and thinner tonality to the mids. The tangzus do not exhibit any thinness nor are they overly thick or bloated. It is the goldilock's zone. Slightly warm due to that surprising bass maybe? but overall instrumentation sounds very nice

Highs:
If I had to nitpick perhaps things like vocals exhibit a little more grain than on something like the HD650. Not a surprise or even a terrible thing, most IEMs have a lot of low/mid treble. However this is extremely controlled and has a good amount of what feels like upper treble too.

Technicalities:
Uhhh. it's 20 bucks. who cares lmao? just kidding.
So obviously soundstage width is nothing crazy, not like an open back like the HD650 or anything. But the imaging? As far as I can tell it's accurate. At least as accurate as any other IEM I’ve tried
Details and separation? Apart from chu this is the most detailed songs have ever been. Even then I think it tends to have more details in bass so overall, very very good. None of the frequencies are masking each other. """""speed""""" of the driver is more than fine

Conclusion:
I'm trying my best not to hop blindfolded here on the hype train but man it's chugging. The wan'er is neutral and smooth. it plays every sound that's thrown at it. Plays it well. What more can you ask for?

The point of this review is not simply to gush over this single IEM. it is to show you a small piece of the journey. Within a single year, maybe two, IEMs have SERIOUSLY become incredible. This hobby used to be one where if your iem could even reproduce frequencies from 50hz below and 15khz up you were privileged. Nowadays? The TUNING that people can get now for cheap? it's nothing other than jaw dropping. Listen, if you have a crazy $5000 end game 26 BA + 12 EST freaking Area 51 iem will this little tangzu impress you? maybe not. But the fact that this sound is available at this price? and it's not the only one either! But the wan'er itself has set the expectations and bar very high. Do yourself a favor and don't ever settle for less than this. Buy these as stocking stuffers, for kids, adults, musicians(especially), whoever and whatever. Because this is what music is supposed to sound like. And it should only get better from here. This hobby is ridiculous.

For 20$ this is quite ridiculous. Balanced armatures are sweet

EDIT-ok spending more time with these the sound is really something special. I'm not even using any fancy amps, heck this audio output is straight from my laptop(nice soundcard). Every note just begins and ends perfectly. Comfort is better with the stock "small" tip. Really the biggest turnoff for any person would be the whole deep seal needed. It's a major headache at first which is why I don't think these will suit kids. But audiophiles on a budget? Oh yes

Will do a full review if you guys want me to

Ok, so this review isn't going to be nearly as long as my first one. There are just a few things I want to address with these coming from much cheaper setups.

First, the build quality.
These seem built very sturdy. The stock cable is phenomenal and I really wouldn't see a reason to "upgrade", especially with so much of the controversy surrounding the actual audible differences. The only minor complaint I have buildwise is how the hinges when swinging horizontally sometimes *click* and the action isn't smooth. It's not a very good feeling and it makes me think that they're going to break or something. 

These do clamp on your head but I am very used to that sort of thing, doesn't bother me one bit especially with these comfy velours. these are by far the comfiest headphones I've worn. They are heavier but it isn't an issue because the padding is sufficient.

Now about the sound. Coming from studio monitors, I notice that it's a lot smoother. I was shocked when I first heard it. Coming from a bright headphone and hearing so much about that "sennheiser veil" I thought it would sound a little muffled at first. Nope. The treble is lovely and never overextends, a problem I sometimes had with the superlux.
I am also surprised at how well balanced the bass is. It is never overpowering, always modest but audible. These have a slight warm tilt but it makes these sound very musical imo. Reminds me a bit of my m50 yet with less bass emphasis and faster with better separation. 
By far though, the best thing about these are the improved mids. The mids are so smooth. They are more forward than the superlux, and more natural than the m50. It's not necessarily that I "hear" more with the hd650 because tbh I don't think I really do. It just sounds a lot less distant and disconnected from the other frequencies.

EDIT- I feel like these will be the last headphones I buy for a long time. Unless it's just for fun to compare I don't think many can oust the hd650. This is almost sonic perfection, or as close as you can get to it without humongous over-the-top setups which may give a smudge of more detail and clarity. But ultimately, the music is what counts and it's never been this enjoyable before. 

First off, this is my first review on this site and I'm by no means an audiophile(still a noob with this stuff, so take what I say lightly/offer suggestions)
I got interested in high quality sound about a year ago.
My first "real" pair of headphones was the ath m50 so I'm going to be comparing these to those and maybe a few other earbuds and whatnot that I've also picked up

Build Quality
Initially, out of the box these looked really good. They are detachable, and come with two cables out of the box. One is like 10ft(previously said 5, it's actually much longer.) and the other is shorter. The headband has bumps on the top like the akg701 but they don't bother me at all. They're very nice and don't drive into your head like the k701s. They have pleather earpads, probably exchangeable with dt770 velours. They don't rattle a lot, and only for a little while did they *creak* a bit when I moved my head around but much less than my m50s.  For 40$, heck for the full retail price...they look legit

Comfort
The comfort at first for these was very weird. I wasn't used to any headphone like this so the self adjusting headband was confusing but eventually I got that. Also, they initially clamped down pretty hard. The pleather pads really hurt my ears but when I moved them around and after a lot of use they are very comfy. Overall they have *slightly* less comfort than my m50s but less clamping force and they don't get as hot. I can wear these for hours with no problem.

Sound
annd finally...the sound
These are paired up with a simple fiiO e7

My Gosh. I felt like I robbed someone when I bought these for this price. Simply amazing.
At first, with no burn in out of the box these sounded pretty neutral. They sounded somewhat similar to my sennheiser 428s. However, something was missing, they were....congested.
The sound was all cluttered together and was "robotic" if that makes sense

With some burn in, everything changed.
The bass went DEEP. The instrument separation was amazing. Not only could I hear background sounds that I never heard before, I could hear them throughout the entire frequency response.

Now for the comparison on how they perform compared to the famous m50
Bass
Despite being semi open, the 681 evo has good bass response. There is no or very little mid bass hump, and the sub bass doesn't die down until about 25hz or so. They extend deep, very deep for what they are.
The ath m50 has more bass and is more impactful, but the hd681 evo is slightly more controlled. Overall, the winner is the m50 here
m50-fun, more wild and exciting, better for bassheads
681 evo-damn accurate. 
 
Mids
The hd 681 evo doesn't dip during the mids as far as I can tell. The m50 has a slight midbass hump and the upper mids can be veiled. They actually sound quite similar here. No big difference except the 681 evos represents high mids better and you can hear more with them because of the separation. 
Winner-681 evo

Highs
A lot of people complained about the original 681s about having ear-rape levels of treble. That's not the case here. The 681 evo highs are very present but they never cause fatigue. They roll off  longer than the m50. Not sure what that means but the m50 has "punchier" highs. You hear the hi-hats and cymbal crashes of the evo longer but they don't sound like sibilance nor are they harsh.
m50 has slightly harsher highs.
Winner-681 evo

Soundstage
no contest. The ath m50 holds up pretty well and the soundstage isn't bad at all. But the 681 evo destroys it here. When I was playing Bioshock infinite, at the loading screen it literally sounded like a 50s radio was sitting 2 feet in front of me playing music. I was shocked, I thought my fiiO e7 had unlocked and the sound was coming from my speakers....it wasn't.

Detail
When I got my little amp/DAC and paired it up with the m50, I was in sound heaven. The detail retrieval was excellent.
The 681 evos took it a tiny step further.
With the m50, I could hear tiny details otherwise inaudible
with the 681 evos, i could hear tiny details otherwise inaudible...throughout the entire song

overall, I am very impressed with these headphones. I've never heard or tried anything better. So I don't know how these would stack up to higher end setups. But for 40$, even for retail value they are great. The m50 is a better beginner headphone but they cost more. So if there are any beginners out there who can afford a simple amp/DAC(they rely on amping more than the m50), then you really can't go wrong

inthere-thanks, glad you liked the review. I'm surprised at how long it was in the end lol..0
Anyways, the 681 evo actually has impedance than the m50 but the decibel level is lower. It should work with the iphone but don't expect it to be fully powered. 

I'll confirm or deny for sure later. That's my guess in the meantime

EDIT- I just got the modi/magni stack. These seem even more detailed before which is remarkable. The difference is microscopic, but audible. Soundstage is even more impressive. I will check to see if my m50 improves even more than these did from the switch.
Oh and inthere...Sorry man but it is physically impossible to go back to the sound of an ipod with these lol. They aren't portable, and they'll look kinda silly if you walk with them outside
EDIT 2.0- After quite a few hours of listening, these are actually quite bright as a consequence of the amping/DAC. I do think that the magni amp contributes and magnifies the treble(pun intended). If you're using these with an amp, prepare for a treble peak. nothing too bad, but it's definitely elevated by a few decibels.
2.1-So dissapointing though...Because if I could reduce the top frequencies by literally TWO decibels, they would be absolutely perfect. And I really do mean that. Perfect.