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:
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:
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:
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:
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:
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:
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:
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):
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:
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.
------------
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/
The HE400i is quite light and fits quite well on my head:
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:
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:
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:
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:
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:
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:
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):
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:
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.
------------
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/
