The HiFiMan table was the first table I saw when I entered the meet area and they had just finished setting up (from what I was told). I met Peter and Summer (both really nice people) and chatted for a bit. The HE-560 (revised model) was being used at the time, so I took a stab at the HE-400i.
Before I continue further, I should note that it was noisy at the meet (as one could assume) and the music used to test wasn't mine. Though I tried my best to find songs/artists/albums that I was familiar with (or closer to what I am familiar with).
HE-400i
HE-400i
The first thing that I did notice about the 400i was that it was smoother in the midrange with good vocal dynamics. The upper midrange clarity was actually quite strong as well. The bass was thicker and had great presence due to the larger body; it had good depth. Though the treble was more laid back in nature, it still offered good detailing and extension. It was quite a warm and easy headphone to listen to.
HE-560
The 560 in contrast was more neutral as a whole (the most neutral of the 4 new planars I auditioned). The treble had a softer edge to it, compared to the Oppo models, despite having greater quantity. The treble did also have great detailing and extension up high. Something that really stood out for me with the 560 was the lower treble and snaps that provided energy. They did hold a bit of air to them as well. The 560 has a slightly larger focus on the lower-midrange in contrast to the 400i, it's quite detailed, but didn't feel analytical or clinical in any way (I felt that the PM-2 did sound somewhat clinical in the mids).
It's been over a month since I've heard the original 560s (and I do miss them, it was a treat to hear the new ones though). So take this with a second grain of salt. I feel that the new 560 is a little stronger with the detailing in the lower-midrange as the older model was quite smooth in this area. It also seemed to have a smaller bass body, but was still punchy and had good texturing down low. Though the treble quantity didn't change, the other changes (in the midrange mainly) made it seem brighter.
HE-400i vs HE-560
As you could guess, the signatures of these two headphones are quite different (they are designed to be). From what I've read, and some of what I heard, the 400i are supposed to be tailored closer to what the HE-500 originally offered. It's warmer and more relaxed in nature than the more neutral 560. The 400i has a bigger bass body though both have great depth and presence as a whole. The 560's midrange isn't as energetic as the 400i's either. As stated, treble is more up front with the 560.
Designs
In terms of the new design, I'm happy with it. The wood may not be as thick anymore, or actual hardwood, but the hard-cut lines from the Veneer work very well with the hard-cut lines of the headphone design overall. The entire design of the 560 has a matted look to it that is more mature as a whole. Overall, I actually do prefer the new look as it has more complexity to the design. The hard-cutting lines also make it look less boring. Though I was told that the wood veneer on the 560 were the same, one did seem to have more of a red-orange hue to it.
In contrast to the matted mature look of the 560, the 400i has a fun glossy design to it. The housing shape is similar and it's colored in a deep bluish-silver-slate color. It's quite attractive and actually looks more flashy than the 560, though the 560's design is much more complex.
Comfort and Fit
The fit on both headphones was great. The pads have been revised a little to have a bigger inner-diameter (from what I was told) which should help quite a few people out. They fit perfectly fine and were comfortable. For me anyway, the fit was unchanged (I have a small head and small ears). With that said, I expect them to be comfortable in the long run as well (having used the 560 extensively before returning them). A note on the weight, by hand, there wasn't much difference between them. Though the 560 measures heavier than the 400i, it didn't feel it on the head or in the hands.