I've owned the Sony MDR-MA900 for about four months now, I got them because I wanted something with more relaxed treble and a bigger soundstage than my K240. My AKG K612 Pro's were a gift from a close friend and I have owned them for about a month now. I find both of these headphones a bit overlooked, although the K612 is the more overlooked of the two and less have seemed to of tried it. I am amping both with an Hifiman EF2A(nos tubes) and an ASUS Xonar DX as the DAC. When it comes to music and genres; I listen to everything and anything and I also game and watch movies, so the comparisons between the two will be taking in all these factors; thus I am comparing the headphones as all-rounders. This review is a bit of a work in progress, I will add more to the review as I compare them more in-depth later on.
Build Quality and Comfort:
K612: The K612 Pro is a well built headphone, doesn't feel cheap or poorly made, the plastic is of high quality and has a substantial feel to it while being quite light. Has a slightly floppy feel because of the headband, but it doesn't take away from the quality if anything makes them more durable. The cable is non-removable but seems flexible and sturdy, it's a well made cable in my opinion. My K612 Pro is made in Austria, it's possible they may make them in China later on but all current K612s are made in Austria as far as I can tell. Comfort wise I found these slightly clampy at first and the pads a tad too stiff and hard, with use the clamp and pads soften up and ends up very comfortable. I don't even notice the headband so headband comfort is great.
MA900: I find the MA900 overall a well-built headphone, it's thin and a bit flimsy feeling but overall they feel well-made and more durable than they initially appear. They seem to be made of a mixture of plastic and a magnesium alloy like some other Sony headphones have been made out of. They are made in Thailand as it says on the cable termination. The headband makes a slight creaking noise at times when you extend it to put on your head. The cable is a bit thin and is a little stiffer than the K612s cable, the terminating jack seems to be a bit cheaper made than other headphones. Comfort is one of the aspects where these headphones really stick out, the earcups are deep and very comfy and the headphone is insanely light-weight. Clamp is very light and non-existent. I did find the headband somewhat noticeable at first but it became more comfortable as I used it more.
Build Quality: K612
Comfort: MA900
Soundstage and Imaging:
K612: The K612 has an accurate and natural sounding soundstage, it's big, but it's nothing that sticks out as abnormal, rather it's well integrated in it's overall sound signature. The imaging is great on this headphone, very accurate and presents a nice feeling of where the sound is coming from, this makes it very good for music and games that take advantage of good imaging.
MA900: The MA900 has a huge soundstage and with that a big sound on top of that. This leaves a very cinematic experience few headphones can achieve, it can sound a tad too big at times. The imaging is good and accurate, but it's not quite as precise as the K612s.
Soundstage: MA900
Imaging: K612
Transparency and Detail:
K612: The K612 is the more detailed and revealing of the two headphones, you hear subtle textures and minute details you just can't hear on the MA900. There is also a greater dynamic range in the sound on the K612, this can be heard with vocals and various instruments, the MA900 sounds a bit more compressed and flat in terms of dynamics. You get a greater sense of clarity and transparency, the vocals and instruments sound more authentic and as if it's not coming from the headphone more often with the K612.
MA900: The MA900 is a bit less detailed but is still a detailed headphone for it's price range. It does seem to lack slightly in terms of transparency, there is a slight veil in the sound and sounds a tad ill-defined at times when compared to the K612.
Transparency and Detail: K612
Bass:
K612: The bass on the K612 is well textured, I found I get more information and texture out of the bass than the MA900. The bass is very linear from upper, mid, to sub bass, doesn't seem to emphasize any region of the bass over the other. It has a thick, present, and robust feel to it. There is also good extension in the sub bass, it extends further in the sub-bass than the MA900, you get the deep subbass rumble with these headphones if the track calls for it.
MA900: I find the bass on the MA900 quite textured and detailed, not quite to the K612s level but it isn't a slouch in this area. There is a slight mid-bass hump in the sound of these headphones, so when a song calls for mid-bass it's a bit more prominent than the K612s. The bass isn't quite as thick and solid sounding as the K612s bass though and it does lack some sub-bass extension.
Bass: K612
Midrange:
K612: This is where this headphone really shines, the midrange is very linear and natural sounding. It's simply beautiful and can give an eerie spine-shivering experience with certain vocal tracks, there is a texture and resolution in the midrange that just isn't found on the MA900. The midrange is neither forward or too laid-back, it's just right. It's clear and pristine.
MA900: This headphone has a pretty good midrange, but it does seem to lack a bit in texture, detail, and transparency when compared to the K612, but it's a good midrange nonetheless. It does seem to have an emphasis in the lower midrange to give it a warmer sound, but this takes away from it having a more pristine midrange.
Midrange: K612
Treble:
K612: The treble of this headphone is linear and pretty much grain-free, it doesn't seem to over emphasize anything, it's neither dark or bright, it's just right, there is a slight roll-off in upper treble though. I find the treble adds a certain beauty and air to the sound and the headphone isn't veiled in any way in the treble. The treble is more detailed and refined than the MA900s treble. It's a very unoffensive treble and isn't sibilant or anything, but it will reveal if a track is overly sibilant but won't thrash your ears.
MA900: The treble in this headphone is slightly dark and laid-back, but also has a little more grain than the K612s treble. It's more rolled-off in the treble than K612 as well and there is less sense of detail and refinement to the treble, but the headphone still has plenty of air to it's sound due to it's large soundstage. The treble isn't sibilant and is unoffensive.
Treble: K612
Conclusion:
The two headphones are both good headphones, but the K612 clearly wins sonically to my ears. In terms of amplification, the K612 is harder to amp and is also pickier about the dac and source than the MA900. Although I do find the MA900 performs best when amped, it sounds thin and a little harsh in the upper regions when not amped and without a decent dac behind it. I personally recommend both the headphones to be amped and have a decent dac behind them. The MA900 doesn't seem like it needs amplification but it does in my experience. Both headphones are great in the ~$200 range and sound different, but the K612 sounds like it's a league above in my ears. The resolution, texture, transparency, forgiving yet revealing sound, better dynamic range, better extension, etc. put the headphone in another class to my ears sonically. And currently the K612 is cheaper than the MA900.
In terms of overall sonic signature alone(not including transparency, refinement, detail, etc.) both are on the unoffensive side and both are headphones you can basically listen to all day. I find the MA900 a bit more laid-back sounding and more of a soundstage lovers headphones. The K612 is more of a neutrality lovers headphones and is more engaging sounding overall. I can see people swaying either way on which they like more and which you will like better will often come down to personal preference and system
