The Massdrop Fostex TH-x00 headphones are an impressive looking set of headphones. The build quality of the Massdrop Fostex TH-x00 is fantastic for the price, very good and solid. Most of the structure of the headphones is magnesium alloy. The headphones are easily adjustable and have notches in the metal supports at each location so that the headphones can lock in place at each location. The one ding I will give on the frame, the same problem which has plagued similar Fostex and Denon headphones, is the single pivot pin between the yoke and the headband. The pivot pin feels inherently weak as it has in previous designs. That's not to say that it is weak, but just that it feels like the headphones could break at the junction much more easily than in other locations. The headband has a minimal amount of padding and is covered in what appears to be synthetic leather or pleather. The earpads are made from the same material as the headband, the padding in the earpads is adequate. The earpads have a slight front to back wedge to them, placing the drivers at a slightly forward facing angle when on your head. I will state that the inner cut out shape of each earpad is not circular but more "O" shaped in nature and offset towards the front of each side. While this was not an issue for me, someone who has relatively small ears, this may be a problem for someone with larger ears. The cord....oh the cord...well first it's not detachable and second it's way too long. At 10 feet, I can't see anyone ever being able to use these as anything other than for home or studio use, and even then the cord still seems too long. I could literally get up from my desk and walk from one wall of the room to the other and have no issues with the cord being too short, it's that long. I will also say that while the main thicker cable doesn't suffer from microphonics, after the break into the two smaller cords up to the drivers, these wires have worse microphonics than I would like from a set of headphones costing $400. Rubbing against your shirt or touching it during normal use will lead to an annoying rustling sound. That all being said the pieces de resistance of these headphones are definitely the beautiful high-gloss mahogany earcups. These things are absolutely gorgeous and, to me, look much better than what was depicted on the Massdrop page. While no two will be alike, given that the mahogany is a natural and unique material, I can't imagine these looking bad. 

Overall, I would give these headphones an 8/10 for build quality.

Things to improve would be the pleather covering on the headband, and earpads. and the rotational pin at the yoke that seems weak. The cord length also needs to be adjusted and detachability is also lacking.

Comfort

These headphones are very comfortable for their size. They definitely are not lightweight, but I wouldn't call them heavyweights either. They are somewhere in between. In comparison to headphones like the Audez'e LCD-2 or HiFiMan HE-500, with their much heavier drivers, these headphones are much lighter. At first, I was concerned with the small amount of padding on the headband when I originally received these, but overall the headband is comfortable and the weight does not seem too much for the thin padding. How this wears over time will be interesting to see as the upper part of the headband feels like a solid band of either metal or plastic that could potentially wear through the pleather coating over time. The clamping pressure on these headphones is reasonable, if not fairly light given the weight. The stock earpads are relatively comfortable, but I could see them becoming sweaty in hotter summer weather as I have a feeling that the synthetic leather probably will not breath that well, but that is an assumption at this point. Ultimately, while I wouldn't put them on par with what I consider some of the most comfortable pair of headphones I've ever worn, the Beyerdynamic Tesla T1 or the Audio Technica ATH-AD2000, I would put them several notches above something such as the Audio Technica ATH-M50 which have much stiffer stock earpads and put more clamping force on the sides of your head. As stated above, I would also put them leaps and bounds ahead of Audez'e or HiFiMan planar magnetic headphones, which weigh substantially more and will put more weight on the top of your head through the headband, which can be too much for some people.
 
I give these headphones an 8/10 for comfort.
 

Sound Quality

So let me get this out of the way first: The straight out of the box sound quality on these without any Amp/DAC is not good for their price. If you plan to use these without an Amp/DAC on computer, on a portable listening device, or other piece of audio equipment that does allow for additional power to be supplied to these headphones, you will disappointed. When trying this on several devices including straight from my computer, on my portable audio device, and from my phone left me asking what was to like about these headphones? The treble, compared to even my ATH-M50, was severely lacking in many instances, which left me feeling like I was missing parts of the recording. Mids and bass seemed muddy albeit very forward. But why should we expect a $400 pair of headphones geared towards audiophiles to perform well in these conditions? Frankly, we shouldn't. If you're going to spend this kind of money on headphones, they certainly deserve to be driven by an appropriate source with good audio quality. Given how ridiculously long the cord is, and the highly polished ear cups, I wouldn't see why someone would want to travel with these anyways. Therefore, the rest of this review, in regards to sound, will be on my current home rig.
 

Testing rig:

1. Schiit Jotunheim w/ built-in DAC connected to computer through USB set to High Gain, volume at approximately 12 o clock.
2. Music files are all lossless, FLAC, or at the very least 320kbps files 
3. Sound comparisons will be made to some of my current headphones

 

Overall, when plugged into the Jotunheim, treble becomes more present. On songs such as Peter Gabriel - Apres Moi, which has strings, brass, and the lovely vocals of Peter Gabriel. The high end becomes more pronounced and defined. Mids slightly more recessed and bass less muddy than without proper sourcing and amp. Overall, I would say these have a "U" or "V" shaped sound profile, but would argue that the bass is more present than the treble. Even with a proper amp, I feel like some sibilant highs in sounds, such as from Melancholia from the Sicario soundtrack, are lost. That all being said, let's break this into categories so that my own review doesn't get too muddy itself.

Bass Quality/Quantity

First and foremost, you may be asking yourself: "these are Fostex, how is the bass?" To answer that I will say that, for the price these are at, the bass quantity is very good. That being said, if you are a basshead I still think these headphones will keep you longing for more. These reach very deep into the bass spectrum, but cuts short of similar headphones such as the Fostex TH-600 or TH-900. 
 
In regards to quality, in my opinion the bass can become muddy and less defined or punchy than I would like on certain tracks. Furthering that, even on tracks where the bass is deliberately more punchy such as on EDM tracks, I would continue by saying the bass is less well defined than my ears would prefer. Tracks like Miike Snow - Genghis Khan make this very noticeable. While the snare and bass drum kicks seem relatively well defined, the background bass seems to reverberate much longer and wider than I have heard on other headphones. Headphones that have arguably less bass quantity such as the Audio Technica ATH-M50 performed much better on these types of tracks when it comes to accuracy, albeit with less quantity and low end. On tracks such as Kings of Leon - Waste A Moment, where there is a lot of high end guitar action, drums, and heavy bass guitar further this point leading to an extremely muddy performance that lacks definition and precision and often seems to get interfered with when a lot of action is happening in the mids and highs.
 
Overall, I would give these:
 
5/10 for bass quality, mainly due to the inherent muddiness or bloated nature on many tracks.
8/10 for bass quantity, not as good as some closed backs, but good given the price range
6.5/10 for bass overall, grading quality and quantity evenly
 

Mids/Treble

As eluded to earlier, the mids are definitely recessed due to the "U" or "V" like sound signature of these cans. That being said the mids are still pronounced enough to be likeable in a lot of situations. Normal male vocals such as Rob Thomas from Matchbox Twenty on If You're Gone sound good and are relatively forward. However, when you start venture upwards to someone like Billy Corgan from Smashing Pumpkins on Disarm, or to even higher heights such as Bon Iver or female vocalists, the mids begin to lose body and substance and the recessed nature becomes much more prevalent.

In regards to the treble, I believe the bass is definitely more pronounced than the treble leading to my statement about the V shape not having the same legs on both sides. I've had mixed reviews in regards to treble with these cans depending on the track. In some instances even with proper source and amping, I have felt parts of songs sound different mainly due to the treble being more recessed than what I am used to. However, in some instances, the treble has seemed extremely sibilant and shrill, almost to levels that are unpleasant. Albeit, not as bad as the TH-600 before it. An example of this is in Puscifer - The Remedy, at around 1 minute there is an accompanying keyboard in the background that on my Audio Technica, Beyerdynamic T1, and even planar magnetics is extremely well defined and forward to a point of almost sibilance. These headphones leave me searching for that same sound, it's there but definitely much more recessed than on other cans.

Overall I would give the Mids a 5/10 as they just are not as forward across the spectrum as I would like. In tracks where both female and male vocals were present such as on the aforementioned Puscifer - The Remedy the vocals smear and the female vocals become more recessed than Maynard's male vocals. To me this leads to a lack of mid range detail which I do not prefer.

In regards to the treble, it depends on what your tolerance level is in terms of sibilant highs. While I think overall the highs are presented nicely, I also believe that it is track dependent, and when they really shine through they can become too sibilant and therefore too much for my ears.

I would give the Treble a rating of 6/10 based on the idea that you like to hearing the highs in songs and are willing to put up with sibilance in some tracks. Should you be sensitive to treble, this would receive a much lower rating.

Sound-stage

The sound stage on these cans is not great. Given that they are "closed back" headphones, albeit these particular headphones leak a lot of sound, I don't think we should expect an immense sound stage. In regards to closed back variants, I would put Mr. Speakers Alpha Dog/Alpha Prime as some of the best in this category, but those headphones also have a very unique internal structure inside of them to do so. The level of airiness is lacking, and the sound stage overall feels very forward. I would say that the sound stage is center of your head in regards to how confined it feels. Separation of instruments on orchestral tracks, or tracks where a lot of vocals and different instruments are present is lacking. In certain instances it almost feels like all of the instruments are stacked on each other playing towards you from the same location and distance leading to an overall lack of width in the sound and also a lack of precise placement.

Sound stage gets 5/10 considering comparable closed-back headphones listed above.

Final Thoughts

I've read many reviewers say that these are "end-game" headphones. These are by no means "end-game" headphones.  The mid range will be too recessed and lacking detail for most. Furthermore, depending on the track the bass and treble seem to have varied issues (bass in muddiness and definement, treble in lack of clarity or too much shrill sibilance.) Furthermore, details such as the ridiculously long thick cord and amount of sound leakage these have, make these headphones virtually unusable for anything other than home use. While that is not a deal breaker for me in particular, I can guess than many head-fi'ers would find this one. While overall I am not disappointed at all for $400, given the gorgeous craftmanship, and overall comfort of these headphones, when it comes down to the nitty gritty of sound performance, these headphones have many areas for improvement. Even in my list above, I have found better headphones overall when compared to the Fostex TH-x00. Given that you can find LCD-2, Tesla T1, ZMF's, or Alpha Dogs used for only slightly more than what these sell for, and can obtain used HiFiMan HE-500 or new HE-400i's at a comparable price point, I would recommend looking elsewhere.