I had a chance to listen to these headphones this week for the first time. An old audio friend dropped by last weekend and brought these with him. He knew I was evaluating a new amp (WA22) and thought I might like to try these with it. He bought them back before Christmas for $250. This surprised me since I remember when I was looking to try some HiFiMan planars a few years ago. The 400i was going for $500 at that time. I ended up deciding to try the HE-560s instead and have been enjoying them ever since. So, I never had tried the 400i's.
He had a couple of extra cables - a balanced cable terminated with a 2.5mm TRRS and a balanced cable with a 4 pin XLR. This gave me chance to try them SE and balanced on my amps and to listen via the balanced out on my DAP.
Comfort was good, not quite as good as the 560s, but that's just my head - YMMV. Clamping was comfortable with the stock pads. These are low Z (around 50 Ohms, I think) and moderately sensitive, open back phones. As with most low Z phones, you can drive these with a cellphone or tablet and make them sound loud. But loud isn't same as good. These phones perform better when driven by something that can source a little more current than a cellphone, tablet or inexpensive DAP. I ran the 400i's off a couple of desktop amps - the Woo WA22 and my reference Violectric 281. I also used the Fiio Mont Blanc E12 portable amp (my favorite). This little amp has some oomph and drove the 400i's quite well. It's a shame it has been discontinued as I thought it was one of the best amps in its price range.
I listened to a variety of tunes - classic rock, jazz and classical. The basics were there as one would expect from open-back planar phones - punchy bass and an airy top end. Without going into a bunch of audiophile gibberish, the 400i could be called a bit less fluid and refined compared to the 560s. With strings and brass there was a rougher texture to the sound - not offensive, but noticeable when doing a direct comparison with the 560s. The performance overall was surprising though considering these originally sold for $400 less than the 560s.
Given that these are now selling for $220 on Amazon, the 400i's have got to be the planar bargain of the year. If you have been wanting to try some planars, this would be an excellent first step. You get 30 days to try them, so you can't really go wrong. I would suggest some modest amplification with a low Z output to really get the most out of them. Only you can be the judge of their comfort and feel on your head.
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