This is very interesting..so you're saying the free field measurements would have an extended treble response with breakup higher up?
I would really appreciate it if you could kindly provide the average raw frequency response of left and right channels.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:
View attachment 100131
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:
View attachment 100132
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:
View attachment 100133
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:
View attachment 100136
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:
View attachment 100141
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:
View attachment 100138
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:
View attachment 100139
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):
View attachment 100142
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:
View attachment 100145
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/
It is recommended to keep it at -1db ish to prevent the Windows limiter from messing up the sound.
The numerical data is attached to the review. You can average them yourself with that data.
Hmmm. You post this in the 800S thread:In contrast, the HE4XX for example has very low distortion across the board:
That is my guess as well. It is a classic problem with planar magnetic speakers as well.
Very hard to imagine such large EQ changes. But yes, Harman has performed double blind tests where they actually take one headphone and make it sound similar to another. So it absolutely makes a difference and a large one. We are not talking about tiny differences between electronics and such.
Where are you seeing it that cheap? Hifiman store says $299 list and $249 on sale with no stock available.
Had*
Wow, big differences in the EQ curves between the two. I'd have to check if the Target Curves are the same to explain the difference, or if the headphone measurements are that different between Oratory & Amir on this headphone. Have you looked into that side of it? (Additionally, it could be a different version of the headphone given what bobbooo posted below).I bought these knowing Amir would measure them one day!
I'm currently using PEQ filters by jaakkopasanen (originally measured by Oratory1990), and posted on 2020-11-18.
I've also imported Amir's posted Roon filters into PEACE (PEQ for Windows):
I assumed -5dB for preamp. On a side note: Is there a formula to calculate it?
Here's a quick comparison between jaakkopasanen and Amir's PEQ filters.
Very nice Amir!
I've listened to both, and they're both worthwhile improvements over original sound.
That's very interesting re the "even more" different versions, and it's possible connection to distortion & soundstage....I would hope this is the case given my HE4XX purchase. It's true there's some differences in those two distortion graphs you posted which Amir highlighted. I suppose we don't know what SPL the one above in your post was measured at? Maybe different equipment? Not sure which one is most valid.Just so everyone's aware, there are not only two main versions of the 400i (this old one, and the new 2020 version), but there were in fact several revisions within the old version too. These revisions included a change to the connector from SMC to 2.5mm, plus the removal of the 'backplate' attached to the rear of the magnet array, the latter having audible effects. What complicates things further is these two revisions were not done at the same time, and not always consistently one after the other, meaning there could actually be four different 'old' 400i sub-versions out there (I've seen users describing three of the four possible permutations of SMC/2.5mm connector and with/without backplate). See here for details. From that thread, the relative differences of measurements by solderdude here, and comparing with Oratory's measurements here, I suspect the unit measured in this review does have the backplate. The measurements here have the wiggles around 200-300 Hz coinciding with excess group delay, suggesting cancellations due to cup reflections, possibly off the backplate. Anecdotally, users have said this makes the backplate versions sound more 'closed-in' with less of an expansive soundstage when compared with versions without the backplate. The backplate versions also show the highest distortion of all the HE4 models. In contrast, the HE4XX for example has very low distortion across the board:
It also does not have a backplate, and so does not suffer from the same earcup reflections and so non-minimum phase behaviour that likely degrades soundstage exhibited by the 400i version measured here, so any inferences about the HE4XX from this review are unfounded; they're very different headphones (not just limited to backplate differences either). As for whether the HE4XX offers the same soundstage as the HD800S, I don't think anyone claimed that - just that the former also has high (but not necessarily quite as much) pinna activation due to its relatively large earcups and driver (angled by the pads). Obviously the HD800S's earcups are larger still so this might illicit a larger sense of space, but I suspect this may partly be down to simply ergonomics and the pads not touching any part of the ear, meaning they 'disappear' more on the head giving more of an illusion of hearing sound coming from an actual outside source. What I don't think the HD800S's soundstage is down to is any mysterious 'technicalities' that you have to pay thousands of dollars for. A more reasonably priced headphone with large angled earcups will do e.g. the Koss ESP/95X (with angled pads) for a thousand dollars less (including amp), which has lower distortion when EQing up the bass to boot (both requiring EQ anyway, as most headphones do).
Hmmm. You post this in the 800S thread:
Unlike what you post jut now, this one shows the clear problems in the mid-range and correlated well with my measurements:
Both show similar distortion in 300 to 400 Hz range and again around 1 to 2 kHz. Yet you said distortion was "nice and low?" Regardless, the correlation is good enough between my measurements and Tyll are good enough that I say we are looking at a real issue here.
Just so everyone's aware, there are not only two main versions of the 400i (this old one, and the new 2020 version), but there were in fact several revisions within the old version too. These revisions included a change to the connector from SMC to 2.5mm, plus the removal of the 'backplate' attached to the rear of the magnet array, the latter having audible effects. What complicates things further is these two revisions were not done at the same time, and not always consistently one after the other, meaning there could actually be four different 'old' 400i sub-versions out there (I've seen users describing three of the four possible permutations of SMC/2.5mm connector and with/without backplate). See here for details. From that thread, the relative differences of measurements by solderdude here, and comparing with Oratory's measurements here, I suspect the unit measured in this review does have the backplate. The measurements here have the wiggles around 200-300 Hz coinciding with excess group delay, suggesting cancellations due to cup reflections, possibly off the backplate. Anecdotally, users have said this makes the backplate versions sound more 'closed-in' with less of an expansive soundstage when compared with versions without the backplate. The backplate versions also show the highest distortion of all the HE4 models. In contrast, the HE4XX for example has very low distortion across the board:
It also does not have a backplate, and so does not suffer from the same earcup reflections and so non-minimum phase behaviour that likely degrades soundstage exhibited by the 400i version measured here, so any inferences about the HE4XX from this review are unfounded; they're very different headphones (not just limited to backplate differences either). As for whether the HE4XX offers the same soundstage as the HD800S, I don't think anyone claimed that - just that the former also has high (but not necessarily quite as much) pinna activation due to its relatively large earcups and driver (angled by the pads). Obviously the HD800S's earcups are larger still so this might illicit a larger sense of space, but I suspect this may partly be down to simply ergonomics and the pads not touching any part of the ear, meaning they 'disappear' more on the head giving more of an illusion of hearing sound coming from an actual outside source. What I don't think the HD800S's soundstage is down to is any mysterious 'technicalities' that you have to pay thousands of dollars for. A more reasonably priced headphone with large angled earcups will do e.g. the Koss ESP/95X (with angled pads) for a thousand dollars less (including amp), which has lower distortion when EQing up the bass to boot (both requiring EQ anyway, as most headphones do).
