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Hifiman HE400i Review (planar headphone)

amirm

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This is a review and detailed measurements of the Hifiman HE400i planar magnetic headphone. I purchased this back in 2017 mainly to test headphone amplifiers. The latest version which I am told is different costs US $185 from Amazon including Prime shipping.

The HE400i is quite light and fits quite well on my head:

HIfiman HE400i Review Planar Headphone.jpg


The stock cord is removable which is nice. As is though, it is stiff, rather short and comes with that odd right angle 3.5mm headphone jack. Seems like they assumed people would be using this in a portable application. For my desktop use all of these are aggravations. I have to use a 1/4 inch adapter with it and the right angle cord gets in the way of my controls. The short cord has also pulled the headphone off my head in more than one occasion.

Here is a zoomed picture of the cup with no informational value:

HIfiman HE400i Review Planar Headphone Cup.jpg


The measurements you are about to see are made using a standardized Gras 45C. I searched for any and all measurements I could find online. Alas while a number of them are close to mine, none are using the exact fixture down to coupler and pinna. As you will see, I have confirmed the approximate accuracy of the measurements using Equalization and listening tests. Ultimately headphone measurements are less exact than speakers above a few kilohertz so keep that in mind as you read these tests.

I have calibrated my headphone fixture with 94 dBSPL test tones and decided that I use the same for headphone measurements. However, instead of using 1 kHz tone I have opted for 425 Hz. This seems to better match research data.

I have also made a lot of progress in building a better test suite for the measurements. More updates and changes will be coming but I am starting to feel good about this set.

Hifiman HE400i (2016) Measurements
There is nothing more important than frequency response of the headphone as each is seemingly different and that difference leaves a very distinct character:

HIfiman HE400i Measurements Frequency Response.png


The ASR preference curve is in sold dashed blue. The red and green are each channel. Matching is pretty good. What is not good is cheating us out of a lot of energy in the all important region of 1 to 3 kHz. Why oh why? This is a common theme among many headphones it seems.

As is usual, bass energy is lower than our target although not as bad as some others I have tested.

What is unusual is all the kinks and noise in the graph. Transfer function of the headphone must be changing in complex ways to create these. Indeed looking at the distortion curve shows us some of this:

HIfiman HE400i Measurements Distortion.png


Someone post that the HE400i is one of the lowest distortion headphones out there. I sure hope not given the above performance! Here is the same data but shown as absolute distortion level rather than percentage:

HIfiman HE400i Measurements Distortion Level.png


I have picked the 40 dB as my tentative threshold level. As we see bass distortion is quite good but we have peaking around 400 Hz and 1.5 kHz.

Oh, in case some of you have trouble reading the frequency response chart and want a more "speaker like" frequency response, here it is:
HIfiman HE400i Measurements Deviation from Reference.png


I use this graph for equalization. Be careful in the troughs toward the end. Do not try to boost those as they are likely cancellations due to reflections inside the cups. We can see this in the group delay graph:

HIfiman HE400i Measurements Group Delay.png


Notice how the frequency response errors between 200 and 300 Hz are repeated here.

I made quick fixture to measure impedance (better one to come soon when I get the precision resistors I ordered):

HIfiman HE400i Measurements Impedance.png


Note that the above display is highly zoomed. Otherwise it would look like a flat line which planar magnetic drivers are known for. As zoomed, the peaks are dependent on how the headphone is mounted. On my head they were lower in frequency than on the fixture.

Hifiman HE400i Headphone Listening Tests
As is, the headphone has a rather "open" sound but nowhere near the spatial effects that the Sennheiser HD800S had. The sound is compressed around a grouping close to my ears. Tonality seems rather dull and closed in. So comes out the EQ tools:

HIfiman HE400i Measurements Equalization.png


Wow, what a difference this made. The sound is now impressive with fantastic dynamics and very clean bass. Detail is improved substantially. On my "speaker killer" tracks without EQ, I could hardly hear the deep notes. With EQ on they came to live without the overall tonality sound like "too much bass." Note how I am lifting the frequencies below 50 Hz or so. It is a bit like adding a subwoofer, not boosting the lows in your speaker. With EQ, I now get deep bass performance that simply does not exist in any bookshelf speaker.

Tracks like Artillery Infected Mushroom sound so much more live with EQ that you can't help but want to bob your head and band on the desk in unison!


Then we swing to the other extreme with Kristin Asbjørnsen's wonderful track, Rain, oh Lord:


As for the distortions we saw in the graphs, I could tell you that I hear them but I am not sure at all. The highs sound a bit shrill at moderate levels. Turning the levels up accentuates this. But this could just be me not trying to EQ above 8 kHz. A shelving filter may help there.

Conclusions
This review was prompted by a member suggesting that the Hifiman HE400i can present that interesting spatial quality that the Sennheiser HD800S. Alas, that is not the case. Maybe there is a hint of that but not more. The frequency response of HE400i shows more bass response which is good but also less energy in the important 1 to 3 kHz region. EQ therefore is mandatory to restore proper balance, resolution, deep bass and detail. Once there, this is a new headphone, producing a very enjoyable experience.

Until I did this test and developed the EQ that you saw, I rarely used the HE400i But now, I am actually anxious to listen to it more! I can't get over how "high fi" it sounds with equalization! :)

I will give the HE400i a pass without equalization. With EQ, I am happy to give the Hifiman HE400i a recommendation.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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imagidominc

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I bought a 400i in 2018 after seeing Amir use it in tests. While I liked its sparkly quality, it certainly became my least used can. I always thought it was too bass light. But the rubbing of bows on string instruments was always particularly beautiful on this headphone.

I just applied Amir's EQ using Roon on this can. Wow, what a difference! Amir was right when he said it takes the 400i from a mid fi can to something almost approximating my HD800! However, I could tell immediately that the sound is way more cramped and not as finely detailed as my HD800, but besides that, it certainly is a great sounding can!

I would caution anybody wanting to buy this can though that the headband is extremely fragile and did break on me, so I had to order a replacement. I know they came out with a 2020 version that has a new headband, but if you are getting this older model, be aware of that.
 
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rodtor

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Thanks very much for this, Amir. These were my favourite headphones until I discovered the virtues of EQing, in part under your influence. The Oratory1990 EQ settings did much more to improve the Sennheiser 6XX's that I also own than they did for these headphones. I'll now try your options. I do think that these phones have a larger sound stage than the 6XX's, but probably can't match the latter in FR, with or without EQing. But I'm not surprised that the 800s have a much superior soundstage. Like others, I am very happy to see you taking on the formidable task of reviewing headphones -- formidable because, as we know from the discussion of the 800s, the spatial dimension of headphone performance may always have to be approached more qualitatively, with less room for precise measurements, than the FR curves.
 

dmac6419

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I have these guess I have to EQ them to see what all the hype is about
 

franspambot

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Wow, Amir. If your reviews are going to be like this, then it is clear that this is a worthwhile project. Thank you for making everything undestandable and useful for us.
 

chych7

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I hope some of the higher end HiFiMan headphones are in your queue. I have the HiFiMan Ananda and it's by far the best sounding device I've heard; sold off my HD650s after I got them. I haven't heard the HD800s, but they supposedly have a soundstage close to the HD800s but with much better bass response.
 

Robbo99999

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Nice, good to see this one reviewed! @amirm , about setting distortion threshold at 40dB, what is your thinking behind choosing 40dB, it seems that 40dB is often below 1% distortion in the frequency response?

I was expecting distortion to look across the frequency range more like the low distortion seen in the bass, but a few issues in distortion further up the frequency range. I'm thinking it's possible that the HE4XX would have less distortion issues than the 400i 2016 version, because the frequency sweep is a bit more "regular" with less of the more extreme dips in the treble. Also I've seen postings of HE4XX distortion being low across the board. Having said this, I have noticed that Amir's measurements for all the headphones he's tested so far seem to be showing somewhat higher distortion than measurements I've seen over on diyaudioheaven and praps some other places.....so it makes me think which ones are the most relevant & why the discrepancies? Could it be explained in equipment differences? Just thinking it through.

I've got an order put in for the Hifiman HE4XX which is the Drop version of the Hifiman HE400i, so I'm hoping it has less distortion than the sample that Amir measured here, but I'm pleased to see the generally positive rating after EQ in the listening tests.

Regarding spaciousness/soundstage, I was/am hoping that the HE4XX has a better soundstage than the HE400i measured here, over on RTINGS I remember seeing the HE4XX having a better soundstage rating the HE400i, and I remember the HE4XX getting one of the best soundstage ratings, higher than AKG K702 for instance (on RTINGS). Thing is, I guess we don't really know how accurate RTings rating of soundstage really is.....they did put Senn 800S right at the top for that parameter, so that marries at least with the 800s reputation & also the listening test by Amir on his glowing take of the soundstage of the 800s.

One thing's for sure, I'm gonna find it interesting when I get my HE4XX when I'm listening for soundstage & distortion....I retain some positivity, I think it'll be better on both fronts than the HE400i measured in this review, but I can't be sure, ha!
 
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amirm

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M00ndancer

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I only use closed HPs today, but I'm curious about open headphones.

They should give me different sound and experience. But people says: Get the Sennhieser 600 or 650, I don't like them or the price. I've been looking for other alternatives.

I really can't get hold of many headphones, so the measurements that @amirm is doing is a great tool to start out with.
 
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amirm

amirm

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Nice, good to see this one reviewed! @amirm , about setting distortion threshold at 40dB, what is your thinking behind choosing 40dB, it seems that 40dB is often below 1% distortion in the frequency response?
No real thought :) other than I set it at 50 dB for speakers and that seems to work. Since headphones are lower distortion, I picked 40 dB tentatively. As we get more mileage on our belt, I may adjust.
 

Woody Stool

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How is Amir applying EQ to these headphones? Can someone kindly explain what gear is used to do this?
 

F1308

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I wonder if they could place an equalizer within the headsets and reach perfection.
 
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amirm

amirm

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Having said this, I have noticed that Amir's measurements for all the headphones he's tested so far seem to be showing somewhat higher distortion than measurements I've seen over on diyaudioheaven and praps some other places.....so it makes me think which ones are the most relevant & why the discrepancies?
I think the real reason is because I have a very different graphing settings than what others use. dB is the standard method and that heavily compresses the peaks due to its log scale. I use linear scale and that allows the peaks to stand out. Also, I am using special signal processing in AP software that extracts the distortion and leaves noise behind. Others include it (showing THD+N vs THD that I use) which can mask distortions.
 
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amirm

amirm

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I wonder if they could place an equalizer within the headsets and reach perfection.
You need power so can't be done in passive headphones. Noise cancelling ones can do this and some indeed have (AKG).
 
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