Sony MDR-EX1000 Overview: The EX1000 is a former flagship IEM released by Sony, only recently discontinued. It features a side-firing 16mm dynamic driver, which is pretty large for an IEM. The form factor of this headphone is a bit peculiar, and they are very visible when worn (I find this a positive rather than a negative). Despite this, they are by far the most comfortable IEMs I've ever used. Comfort has been a huge thing keeping me from pursuing in ears, and these are a huge winner in this regard. They come with a plethora of high quality silicone tips to choose from, with 7 different "hybrid" sizes as well as 3 sizes of tips with additional foam under the silicone to increase isolation for noisy environments. All tips are color-coded by size with the colored portion being the sleeve which goes over the nozzle, which I found clever. Image courtesy of Headfonia.com as the original packaging was not included with the pair I have. Build Quality: The cable on these is a bit soft, which has me worried as I'm reminded of cables that lasted exactly 5 days before having to be replaced with a similar feel to them. It has bendable cable leads at the earphone side, which makes them easy to customize to fit your ear. The cable is also detachable and has a very nice proprietary plug that won't come off on accident. I'm just speculating on cable durability, but even if I'm right the official cable is still readily available, as are DIY plugs that enable you to make your own. Build quality of the housing is very solid. The black portion of the housing is magnesium alloy, while the charcoal gray is a very stiff glossy plastic. The cable detachments are a secure screw-on design and don't move even in the slightest when properly attached. Very solid feeling throughout. Ergonomics, Fit, and Isolation: It quickly became apparent to me that these are not a intended to be a deep-insertion IEM, after instinctually cramming them into my skull. I guess my ER-4 days weren't as far back as I thought. The deeper they're inserted the less comfortable they are, and it seems to interfere with the bass as well as making the treble sound sharper. Personally, I got the best combination of sound and comfort from the SS (extra small) silicone tips, inserted partially. Once I did this, I was greeted with a shockingly comfortable fit that allowed the headphones to eventually disappear entirely. That being said, these do not isolate on the level of a deep insertion IEM like the ER-4. If you need super good isolation, these won't fit the bill, unfortunately. Sound: These things are damn good. Super coherent and tight sounding while being wonderfully balanced and neutral. I found these to actually sound quite competent out of less-than-ideal source material such as my laptop, a little soft/passive and smoothed over, but definitely more than tolerable. Clear, refined, pleasant and linear. Honestly, my laptop was the first source I used these with and my first thought was "why do people think these are bright?" I had trouble noticing the reported sizzle to the lower treble/upper midrange during these tests. All I really heard was fantastic treble extension and maybe the occasional "plasticy" timbre with the wrong song. Switch to the Geek Out 450, holy crap. Now it's slamming super hard with an enormous 3-Dimensional soundstage and tons of resolution everywhere. Very engaging and dynamic sounding. They're also now sounding a tad sharp as others have said, but its hard to tell how much of that is the GO and how much is the EX1k. Whatever the cause, it's far from unlistenable for me. Depending on the track, it can range anywhere from being indistinguishable, to sounding only slightly plasticy, and finally stopping at moderately uncontrolled and sizzly. I've heard worse from an AKG Q701, for sure, and that was never particularly sharp sounding to me, even out of an O2/ODAC. Upper FR anomaly aside, these are one of the most neutral IEMs I've ever used. The Etymotic ER-4S was brighter than these are for sure. Midrange and bass tone is spot on, neither warm nor lean, and very well integrated to where there is not a clear distinction between them. This characteristic is not one that is easily found, in my experience, and only one other headphone I've heard does it this well. There are numerous other IEMs from sony with this form factor, notably the EX600, EX800ST, and MDR-7550, none of which I can recommend over the EX1000. The 1k is the special one for sure. TL;DR: Fantastic Neutral and well extended Extremely tight and coherent sounding No clear disjoint between bass and midrange Bass hits quite hard while remaining clean Super resolving and spacious Clear, separated, dynamic, engaging Scale well with amplification Built very well Ergonomic and comfortable Dubious stock cable Slight tendency to sound bright and plasticy/sizzly with the wrong song Mediocre isolation I'm a bit hard to please, especially with regards to in ears, but these are really enjoyable. Favorite IEM by far. Hell, screw favorite IEM, these are arguably better than each of my home headphones in some way and have been monopolizing my ear time since I got them in the mail.