First of all let me mention that I am very fond of the previous Denon top models, be it the AH-D7000 or the AH-D7100; as such my statements here might be slightly biased... anyway, I will try to be as objective as I can.
After unpacking I was truly amazed. The build-quality is far beyond anything I ever held in my hands with this price tag to it. If anybody would have told me, that it costs twice its price I would have believed so without hesitation. The AH-D7100 was critisised for the excessive usage of plastic. Well here, on the MM400 you will not find lots of plastic parts anymore. Just the silver ring around the wood-cups next to the pads (...and probably some bits and pieces inside). And of course the cable. Anything else is satinized or polished metal, wood with beautiful grain and pleather. WONDERFUL!!!
Here the MM400 shown together with other headphones to get a better impression of it's size:
...further below in the PPS you will find more pics with 1 to 1 comparisons.
Here the MM400 combined with the AK100II:
Also the hinges for folding the MM400 work great:
All in all a pleasure to handle!
It is perfectly comfortable. The pads are soft, they sit not too loose and not too tight, the ears are perfectly covered, no leakages in either direction. The pads even close very well around the side-arms of my glasses.
After a first basic break-in with white-noise (around 20hrs), I conclude as follows:
The typical Denon sound signature is (LUCKILY) still there. A bass with serious substance, combined with a clear and open mid- and high- range.
In comparison to the AH-D7100 the bass emphasis is placed a little higher within the frequency range and reaching further up into the lower mids. On the other hand it is not as dominant as the D7100's bass (...which I actually like a lot...), so luckily the lower mids are not veiled by the bass. Despite the bass emphasis there is no serious coloration recognizable.
With some music I found the bass slightly too present whereas other recordings gaind from it. Especially with orchestral the bass could be a little too full and bloomy, whereas rock, jazz and electronica get lined with the substance they need to sound ''serious'' via headphones. As such to some this might be an advantage to others a disadvantage...
Still, my experience with the D7100 tells me to wait for a final judgement in this respect, because the D7100's mids came more forward with extensive break-in; making the bass sound less dominant resulting in a more balanced sound. If the same is the case with the MM400 as well, then it might become a ''perfect'' allrounder (refer to "PS" below).
Very important to me: The sound is not fatiguing at all, I listened for many hours in one go and every new song is a new engaging & exciting expedition into sound...
Space is good, but surely not as far-projecting as for example a K-702 can be (...if amplified correctly). In comparison to such ultra spatial headphones with the MM400 the soundstage happens closer to headspace. But within this vicinity imaging is definitely very well spot on! In combination with the bass emphasis this can lead to a convincingly live-like sound impression.
The MM400 is easy-driven, whether Astel Kern AK100II, HDVD800, ifi micro iDSD, iPad, iPod classic & touch or any computer output, it worked great!
All in all it is a pleasure to listen to the MM400, together with my Shure SE535 they will make up a great team for my coming travels.
I will amend this review along the coming development of my impressions of the MM400.
PS: ...confirmed, after around 70hrs the mid-range (and high-range) is still coming forward more and more... it sounds pretty much balanced now, whereas if the music requires this headphone still has very substantial punch (as positive as this can be)... just now I listen to Mike Oldfield's "foreign affairs" and "in high places" as DSD (I recently digitize some of my LPs, more info here) and it sounds so good that this is already the 3rd time in a row now...
At around 100hrs I will try classical music again to see whether the MM400 became more of an allrounder and whether orchestral goes better...
Anyway, I am sure now that the MM400 will be one of my most favorite headphones, within the portables THE most favorite one; it is a keeper!
PS2: here some more pics with 1:1 comparisons, starting with the AH-D7100:
Here with the LCD-X:
Here with the HE400:
...and here the pads of the MM400 and the HE400 compared:
Actually the pads used on the Hifiman HE400 are Lawton Audio's angle pads for the Denon AH-D7000. But they perfectly fit my HE400 as well.
The cavity on the Lawton angle pads looks so much bigger (...and actually is so much bigger), but let me confirm, the AH400 pad cavity still well fits around my ears, and I am not exactly a small-eared person. So yes, it can be called a "full size over-ear". And despite the fact of not being as spacious inside the cavity as the other over-ear headphones shown above, it still is large enough to be very comfortable... at least for me.
PS3: I am at around 120hrs now and I come to the impression that the break-in period was over at around 100 hours. Not much change anymore since that. But until there FR has further flattened, for my taste I would call it an allrounder now. Over the past days I listened to SOAD / Mesmerize, Frank Zappa / Sheik Yerbouti, Rush / Moving Pictures, Bob James & Earl Klugh / Cool, Dead can Dance / Anastasis, Hilary Hahn / Silfra, Max Bruch / Violine Concerto... all with the same pleasure! Excellent!
PS4: Here, here and here some talk about maintenance of the MM400.
PS5: Now I own the MM400 since around 6 weeks and I am at about 200 hours. That seems quite a lot for such a short time, around 4.7hours a day... Of course I did not listen to it all the time, I let it run over many nights, breaking it in with pink and white noise.
In 3PS above, at around 120hrs, I mentioned that I thought the break-in process was finished. Well, sorry, I was wrong, and from my experience with the D7100 I actually should have known better.
In a nutshell, the MM400 further improved. Surely the changes are more subtle now. So the general sound signature remained the same: a substantial bass with punch, clear and open mids and highs; an all in all pleasant frequency response with low distortion leading to practically no fatigue and making it feasible for long engaging listening sessions.
Luckily all of that remained as it was. But the sound became even more refined now. In specific this improvement is in the fine-dynamics. The MM400 is now reacting extremely sensitive on even the finest dynamic oscillations. This has the effect that the music is flowing with a wonderful ease. And, if the recording is giving it, it really kind of excites the ear-drums in a most enjoyable way; it kind of tickles on your your ear-drums. I experienced this just yesterday with "Future Sounds Of Jazz Vol 11", DSD64 digitized LP, listened to via the AK100II.
Amazing headphones those are, indeed...
PS6: I can confirm, the FR settled. After now approx 300hrs ob breaking in (of course not only listening but many hrs with white and pink noise...), I can not recognize any further change. As such my conclusion remains as described under PS5... and I remain a happy owner...