Didn't see any reviews on this yet so I guess I'm 1st.
 
I compared this with JDS Labs C5, Fiio E12, E6, Objective 2, Magni 2 Uber, and Schiit Fulla. 
 
Nothing brings to mind the phrase "polishing a turd" like the sound of the unit in my opinion. There are loads of sonic tweaks in the Soundblaster Central app that's free from the iOS app store, but ultimately none that I tried were successful in giving the Creative Soundblaster E5 a more *expensive* sound. Ultimately, the Fiio E6 even had a more "expensive* sound than this imo. 
 
I wanted to love this thing, I really did. Bluetooth connectivity is spot on and the EQ in the software suite is sensational. The "Crystalizer" and "Surround" options sound pretty fake and colored, but maybe that's just my opinion. 
 
The base sound signature is a bit recessed in the mids to my ears, giving it an overall kind of dark hollow feel. The gain switch is supposed to enable it to power high impedance headphones, which I generally stay away from, so I wasn't able to test it with some 600ohm cans. It was powerful enough to run Alpha Dogs and HE-500's fine though. 
 
Battery life I would estimate at about 5 hours in the high gain position and more of course if switched to low gain. 

I have 4 pair of these, all given to me as a result of my job, which is professional DJ. The 1st pair I got had the 1/4 adapter connected(see photo) to the cable permanently so you would never lose it, which I thought was a very nice touch for traveling DJ's because I lose them all the time, but that feature was later removed in the 3 pair I got after that.
The flip up ears are also a very nice touch and in my case at least, very well done because I can flip up an ear and the headphones still fit snuggly. 
 
 Beats gets a bad rap from *audiophiles* who want to seem like they know what they're talking about, and the quickest way to get respect is to slag off Beats. Be aware though that there are an extremely high number of fake Beats out there and if you go to YouTube there are literally hundreds of videos for identifying fakes. So best to buy any kind of Beat from a reputable chain store or you'll most likely get fakes. 
 
 These are by far the loudest headphones I've ever put on my head (not necessarily a good thing, but it does give you versatility with loud sound systems) and it's advertised that you can hear what's going on over any club sound system and that's pretty much correct, but it's the way you can hear that's interesting. They've cut a ton of sub bass out and anything below 100hz is just about gone. On the other hand, you're going to get a boost at around 150-300hz, which gives kick drums a lot of clarity. Ditto for claps/snare/backbeats which gets a boost at 800hz to about 1.5khz. Backbeats stick out like sore thumbs and that makes beatmatching a lot easier. The Sony MDR 700's are no longer industry standard, but comparing the Mixr's to them I'd say the Mixr's have a better soundstage (which isn't usually a good thing for DJ's because you listen with only one ear a lot, but it works) and 
because of the emphasis on kicks and backbeats it really threatens to change the game. The only thing holding it back is the Beats name itself, which has a horrible reputation with professionals. 
 
 It's important to realize what made the Sony MDR 700's so popular for DJ'ing; they were the loudest headphones and they're essentially mono. Customizers cut off an ear and make a phone style monitor with them because the same thing basically comes out of each ear. Pioneers knows about the importance of mono in DJ'ing and even have a mono switch for their HDJ 2000's, which I also own. Mixr's are louder than the Sony's and place emphasis on kicks and backbeats, which the Sony's never did. I'm hoping some other company embraces the concept of EQ'ing kicks and backbeats because I'm embarrassed wearing Beats in public. 
 
 On that note Beats seems to get a bit greedy (what a surprise!) because of the nice soundstage, because they're also going for the portable mp3/iPod crowd. Beats have a problem with store listening because most stores I've been to have a preamp that they run all the headphones through, which because Beats are basically the loudest headphones out, they're going to be the most distorted cans on display. This is actually a smart strategy for stores because Beats are usually going to sell regardless because they're coveted as a fashion accessory more than as a listening device. Boosting the volume of all the other cans while distorting the Beats make them a better choice for people that actually care what they're listening to. In my personal experience though on normal non amplified sources, the Beats distort very little even when cranked all the way up. 
 
Make no mistake; these are DJ headphones and for that specific purpose the Mixr's jump to the head of the pack. For studio work and professional sound engineering they're absolutely useless. Too much added and taken away from key frequencies. For that purpose i would recommend a neutral set like the ATH-M50's. For pleasurable/home/audiophile listening no way as well; they're closed, soundstage not good enough, very harsh overall in the high mids and low mids, and uncomfortable for long listening sessions. 
 
For portable listening (iPods/iPhones/mp3 players) Mixr's are the loudest headphones on the planet and you will never need an external amp. Athough they won't distort at top volume, it still is not a pleasant listening experience to these ears because things get quite a bit harsh and painful, not because it's so loud, but because the aforementioned high mids and low mids cut through so sharply.
 
They have a lot more high end and mids than the Studio Beats, and they're louder, but Studio Beats have a warmer overall sound and sub bass, which the Mixr's don't have. 
 
Build quality: they're a LOT sturdier than other Beats. And the pictured cable is from my 1st pair, which still works flawlessly through a LOT of abuse. I had a lot of problems with cabling on the Studio and Solo Beats.

I'm a professional DJ/Producer. In my rider I ask that the venue supply the headphones. So I have at least 100 pairs of headphones, and that's after giving away the majority of them to friends. Not going to bother to run off every pair but I've tried just about every pair out. 
 
Just before I was about to play in Stockholm I received a pair of these Marshall Major FX headphones and out of the box they were noticeably the best sounding portable headphones I'd ever heard. A friend had just come into my room (He's also a DJ) and I let him hear them and his response was the same. He had an iPhone 5 and I had an HTC 8x Windows Phone and the latest generation iPad that I tested them on. We played Simon and Garfunkel, Carly Simon, Van Halen, The Police, and Bill Withers. 
 
My friend begged me not to DJ with the headphones because "they sounded too beautiful and sweet to DJ with" and he thought I may blow them out putting them on the DJ system's headphone jack. I decided to try them out anyway since i got them for free and I figured I'd just but another pair if I blew them. Anyway, I DJ'd with them and it was a beautiful experience, and trust me they took plenty of punishment that night. 
 
Anyway, they quickly became my go-to headphones for air travel and portable listening. Every single music business professional I exposed them to said the same thing: best sounding portables ever. I made it back to Chicago, where my family is, and did a listening test with another roomful of professional and they all agreed. Afterwards, my cousin had gotten a new iPhone and I gave her my beloved Marshalls. No problem, I'd just order a new pair off Amazon or somewhere. 
 
 The new pair came and sounded totally different. Like crap actually. The high end was completely gone. The soundstage was non existent. Everything was muddy as hell. I couldn't believe it. Now normally I would have given them 24 hours of burn in and tried them again, if they didn't sound better I'd toss them aside or give them away. But the problem here was I'd heard these at their absolute best and they were made for GOD. 
 
 So I did 24, then 48 hours of burn in and got only a slight change. I was incensed. What was the problem???? I thought that maybe I'd gotten a defective pair or worse, fake pair. Surely the difference couldn't be THAT [size=small] dissimilar?? [/size]I began emailing Marshall and asking them what the problem was and they suggested that maybe I got a defective pair and they were willing to replace them. I kept burning them in in, playing them on iPods and phones as I slept. 
 
FINALLY, after 3 weeks and 200+ hours of play, I got a noticeable breakthrough. Within the next 5 days, the sound quality was at the very least on par with my previous pair, if not even better! I've never owned a pair of headphone where burn-in made such a radical difference. I contacted Marshall and told them the crisis was over. 
 
 That part deals somewhat with the sound quality, which is phenomenal. 
 
Now, as far as build quality goes, I give low marks because they seem flimsy, but they're actually much sturdier than they look. And the non-replaceable cable is a HUGE downer for me, it means I'll have to buy and possibly burn in another damn pair if the cable craps out. And yes I WILL buy a new pair if that happens without hesitation, because I am now addicted to the sound. Comfort I can't really comment on because you have different sized heads and I've found with on-ears more than any other can that what's nirvana for one guy is hell for the next. These are comfortable for me but they're a snug fit so I'll bet they'll hurt like heck on someone else. 
 
I HAVE to give these 5 stars based on the sound alone.