How does this compare to denon AH-d600 SQ wise?

... actually the midrange (of a completely broken-in) D600 is more forward than the MM400's which some will prefer. The MM400 certainly sound "softer". Luckily this happens without a lack of detail, so the M400 is highly transparent without ever being fatiguing; which can be the case with some music and the D600. So here a small advantage for the M400.
Both sound fabulous with my AK100II. Both are transparent, have wonderful detail, substance and are able to create "realistic" sound images. The D600 has a slightly wider soundstage, this point would go to the D600.
I couldn't say this or that is better, both are different, but each in its way great.
So which one I prefer mainly depends on the music I want to listen to and the mood I am in... and my mood is generally more tending to the MM400 sound signature; and... the MM400 look far better and with their folding mechanism they are far more feasible for mobile usage. All in all so much more fun to handle.
So if I had to decide for one of them (...the old lonely island question...) I would certainly go for the MM400.

I received one PM asking: "(...) A couple of pics of them on compared to other headphones would be fantastic, if you get the chance to do that. (...)". So I added some more pictures combining theMM400 with other headphones to the review. I hope that helps...

Are the earpads removable/replaceable? Same with the cable.

...the cable is a simple "plug and play", it comes with one with mic and one without. I didn't dare to try to get the pads off yet... I will let you know when I did...

Ok. Thanks.

Thank you for the impressions. I am interested.

Received these babies today. Had a 2 hour listening session with them. I am nothing short of impressed. They are a perfectly sized and beautifully built headphone. They are just drop dead gorgeous, one of the nicest pieces of Audio hear I have laid my eyes on.

Sound wise, they are what I wished the P7's were. They have no harshness in the top end. They have no bloating or distortion in the low end. They are just effortless to listen to. Their sound could be best described as buttery smooth. Sound stage isn't as large as it could be. Instrument separation is there. And for those of you looking for a flat response, look elsewhere. They do have bass presence but it doesn't make an appearance when it shouldn't be there. Definitely does not sound anemic but full and enjoyable with all the genres I tried so far. First impressions anyway, if anything changes, I will let you all know.

Edit: I probably should state what I am using them with, which is the Fiio X5. It had no issues driving these. I also gave the headphones more listening time after I got home from work. Wow, these things really come to life with lossless formats. Their soundstage and instrument separation dramatically increases. Their bass is luscious and fast acting. I also noticed something with these I haven't heard before with my previous numerous headphones. With other headphones, there tends to be a predictable sound irrespective of what track you throw at them. With these, each track has its needed character. It strongly reflects the quality of the recording, the emphasis the recording has with different instruments and the way in which it was recorded. For example, I listened to Sting and the Eagles (Hell Freezes Over live). I have both in lossless. For each artist, I had studio and live recordings. I had recordings which were older versus newer. In every instance, I got something unique and reflective of what I was listening to. The old recordings showed their age and imperfections. The new ones showed some of the artificial effects you tend to find with them. The studio recordings felt they were recorded right there. Live recordings displayed the feeling of a full stage with instruments placement quite surprising for closed cans. My previous headphones, particularly my Denons tended to sound more predictable across the board. They also artificially created reverb to make themselves sound more open when in fact they were not, if anything, confused.

@Romani, thanks for your comment. You are right, even if not being the most neutral in the sense of flat FR, they still are very neutral in the sense that they give each recording the space to display its very own character.

...some more about comparing the MM400 to the D7100 here...

...and even more comparing to D7100 and D600

Are these detailed and do the vocals sound forward? Its not a relaxed sound is it??? Please say no :'(

@prolificaudio....they are very detailed, but the voices are not exactly forward. They have the character that is determined by the recording. The MM400 does not "imprint" it's own sound-signature to a recording, it rather emphasizes what is given by the recording. The sound is extremely relaxed in the sense that I feel practically no fatigue from listening to it.

@Prolificaudio , I second @musikaladin
 
This is precisely how I would describe them in terms of detail and vocals!
 
"The MM400 does not "imprint" it's own sound-signature to a recording, it rather emphasizes what is given by the recording".

@Romani.... actually it was you putting my attention to that fact

I think we have similar thoughts on this can @musikaladin. I got them off the back of your review and offline feedback, just in case you forgot

@Romani.... and it is good to know that you like them...

Thanks guys. How much more forwards did the mids come forward? Can any of you tell me of any mid centric headphones? I appreciate any input my friends. musikaladin you have a gorgeous collection by the way.

@profilicaudio, the most mid focused cans I own are the AKG K-702.

are the earcups bigger than the p7's?