The retail package for the IE 80 is one of the most impressive IEM packages I've seen. The IEMs are nicely presented and the brushed aluminium box looks very sleek.

Opening the box confirms this with a the box despite being plastic with aluminium faceplates seems very well constructed and more than adaquetely protects the IEMs themselves although the L shaped 3.5mm connector can be difficult to fit into the case. The included tip selection is very wide. However for me, this is where the problems began.

The tips selection, while wide, is still subpar in design, with many of the buds themselves seems to be designed for freakish ear canals, a fact not helped by the wide nozzle design of the IE series. This made it impossible to get anything approximating a decent fit with any of the included tips. However, since I own a fairly large number of IEMs I made do with some medium Sony Hybrid greys from a pair of MH1cs which stretched over the much wider nozzle of the IE80. It should also be noted that the IE80 provides almost no isolation at all.

Onto sound: With the stock tips, the sound was fairly decent, the large(for an IEM) soundstage remeniscent of the older IE8 is present, imaging is good and the highs are detailed but non fatiguing and the lows are strong and impactful. However the mid range was muddied significantly by the low end, which was extremely disappointing in a £200 pair of IEMs. The highs themselves while technically accurate, left much to be desired in terms of musicality and I found them quite dry and boring, lacking the slight sparkle of other IEMs in the price range(or below) such as the Phonak Audeo PFE112 or the Shure SE425.
Fitting the previously mentioned Sony Hybrid Grey tips on the IE80 attenuated the highs and closed the coundstage noticeably, resulting in a darker smaller sound. I found the trade off for a secure fit and the greater isolation quite favourable however.

Looking on head-fi I came across the tape mod and auvivo tips. The tape mod involves covering the bass ports with tape. This has the effect of removing the midbass bloat that muddies the midrange and tightens the bass up. Depending on what setting you had the bass port on piror to the tape the IE80 shift from a bass centric to a mid centric IEM, which may not be for all listeners. The Auvio tips are Sony Hybrid clones with a central bore width that fits the IE80 wide nozzle naturally and as such doe not reduce the soundstage and attenuate the highs like the normal Sony Hybrids. Similar, but for me an inferior fit are the silicone tips included with JVC IEMs.

In conclusion, the IE80 is a competant IEM, but is highly flawed in it's stock form. Due to the many issues I have with it, I find it difficult to recommend at the £200 price mark it typically sells for in the UK. If you do find youself enjoying the soundof the IE80, but hating the fit, it may be worth investing £120 in some custom silicone eartips from ACS.

Stock sound:
Highs: 7.5/10
Mids: 5/10
Lows: 8/10
Stock Fit: 2/10

Tape Modded sound:
Highs: 7.5/10
Mids: 7/10
Lows 8/10

 
Comfort and build quality:
The KNS8400 comes with wonderfully soft memory foam pleather ear and headband pads. They can get hot after several hours use, but that's expected for closed pleather. They clamp fairly well, not too tight, not too low, I can have a moderate headbang and these headphones won't budge.
The cable is detachable and about 8ft long(as measured with a 15cm ruler). It's not great since it's very long and prone to tangling itself and trying to coil itself back into whatever way it was last stored. There is an additional 1ft extension cable that includes an inline volume control. The cable attaches the the headphones via a twist and lock 2.5mm jack and terminates in a 3.5mm jack with a screw on 6.3mm adaptor.
 
The headphones themselves are made of fairly durable industrial plastic with a metal reinforced headband.
 
Sound:
I tested this out of my Schiit Asgard amp with a Xonar DX as my source, then out of a Fiio E5 with a Sansa Clip+ and finally out of the Asgard with the Sansa Clip+. All music was in either 320kbs MP3 or FLAC 16/44 with the occasional FLAC 24/96 tune.
 
One thing to note is that these headphones are resolving enough to tell if the source was the Clip+ or the DX. If your source sucks, these are going to let you know. These have some serious detail, for instance in a FLAC 24/96 recording of Beethovens Poco Adagio, I could clearly hear every sniffle made by a member of the orchestra. 
 
Highs:
These are kept under control quite impressively and are fairly laid back. This makes it easier to listen to the KNS8400 for extended periods than my Shure SRH840s, which I find quite fatiguing after a couple hours. The laid back sound does mean the highs are less detailed than the Shures. However, the highs are quite sibilant and piercing until the headphones are burned in.
 
Mids:
The mids are neutral, bordering on a slight emphasis. There is nothing really wrong about the mids, the KNS8400 does mids very, very well. Vocals sound fantastic and are very clear. Listening to Marina & the Diamonds was a treat on these headphones, although I would say these headphones do male vocals better than female vocals.
 
Bass:
The bass is present, but not forward. It exists and turns up when needed, the detail is there but not the impact. It is capable of being punchy, but not of the low subbass rumble or slam you get from speakers or from my Denon D2ks. Good for dance, trance and certain dubstep, but not well suited to techno or jazz. The bass needs to be faster to play well with jazz. In comparison to my SRH840s, they have more punch, but less detail and extension.
 
Soundstage:
It's never going to be amazing with closed headphones and as such the soundstage is fairly average. Classical music in particular sounds slightly congested, but the soundstage is wide enough for anything else. Nothing to complain about, but not great either.
 
The rest:
Isolation is pretty average for a closed headphone and the headphones are easy to drive at 36Ω. However they do benefit from some amplification, which helps to bring out the bass and details. Even a lowly E5 does a decent job at amplifying them, but a higher end amp like the Asgard provides better results.
 
In short these headphones have no real weakness, but at the same time no outstanding strengths other than its detail retrieval and low price.

Pros:

1. Quite cheap (I paid £69)
2. Soundstage is fantastic at this price
3. The detachable cable is a great addition at this price point and ensures a much easier repair if the cable fails.
4. The provided foam tips are incredibly isolating and not exactly cheap if you try and buy them separately!
5. Wonderful for vocal music, mids are very good.
6. Surprisingly bassy, it's not overpowering, but it's certainly there and is quite detailed. Possibly too much bass for some.
7. No sibilence in the highs.

 
Cons:

1. The cable to earbud connector is fragile. Don't take the cables off without good reason.
2. No memory wire for the section of cable that goes over the ear, while whatever they are using is decent, it's not great and pretty much ensure I need to have the cord keeper zipped up to my neck to keep the earbuds properly hooked in.
3. Highs roll off a bit too sharply for my liking.

Almost 3 years ago and with the low budget of £20 I set out to buy a pair of reasonable, rugged in ears that could be used as a travel, camping and workout buddy.
These just so happened to be on sale at £8 at the time, although they more usually retail for £12-14.
 
They gave up on me last month, after a fairly traumatic life.
 
While not even close to audiophile sound, they are great for the price, with fairly punchy bass and reasonable trebles. The highs were rather lacking, instead of being able to discern between frequencies, they all merged into a high-frequency gloop, so these would not exactly be good for classical or female vocal music.
 
However, I still struggle to find anything as good for the price and purchased my 2nd pair almost as soon as it became clear my old faithful had broken for good.