This is a review and detailed measurements of the Hifiman HE-6 open-back, Planar Magnetic Headphone. It was kindly loaned to me by a member. There are different versions of this headphone in the wild. This is the "4-screw" version. The HE-6 has been discontinued. When available, it cost US $1,300.
The HE-6 has a serious look to it and beefy metal parts:
I think the wiring provided are aftermarket.
The large cups allowed it to instantly fit on my head with excellent comfort despite its above average weight.
The cup is round and its inside diameter is 60 millimeters. The depth is 18 millimeters.
Note: The measurements you are about to see are preformed using standardized GRAS 45CA headphone measurement fixture. Headphone measurements require more interpretation than speaker tests and have more of a requirement for subjective testing as a result. In addition, comparison of measurements between different people performing it using different configurations requires fair bit of skill. So don't look for matching results. Focus on high level picture. Listening tests are performed using RME ADI-2 DAC and its headphone output.
Mounting the headphone on my test fixture was challenging, resulting in quite a lot of variation between channels and overall response. I optimized this as best as I could but like there are some error in low frequencies.
Hifiman HE-6 Measurements
Before I show the measurement let me state that this was the easiest headphone to measure by far. I just put it on my test rig and it instantly registered equal levels in both cups. And furthermore, the level barely changed when I switched to a low frequency of 80 Hz. It was a joy in this regard!
Let's start with frequency response of HE-6 and comparison to our preference target to figure out tonality of the headphone:
Now you see what I meant by ease of measurements. See how the response is ruler flat and matching in both cups from 20 Hz to almost 1.5 kHz! I have never seen such precision before. Yes, our preferred response asks for more bass but this is a great baseline to have instead of drooping, or jagged response. Someone had a target of flat response there and got it! Beyond 1 kHz, we have some shortfall from target followed by excessive peaking and exaggerated highs. Neither is very extreme though:
Check out the distortion levels:
At 94 and 104 dB, there is essentially no distortion from 20 Hz to 10 kHz! 114 dBSPL brings out some unhappiness between 1 and 2 kHz. We can see that there must be multiple sound sources from the group delay:
Low frequency response though is textbook accurate with that sloping down graph. Again, I don't recall seeing another headphone that clean in that region.
Back to distortion, the HE-6 passes my 40 dBSPL threshold with flying colors:
The HE-6 has a reputation for being very inefficient, needing ton of power and we can see that in my testing:
It is in a class by itself there.
Typical of planar magnetic transducers, impedance is flat and low:
Hifiman HE-6 Listening Tests
I remember testing the HE-6 a couple of weeks ago for another purpose and saying, "hey, this is not bad!" Same impression held this time around. The sound is very clean with just a bit of high frequency exaggeration. What bass there is, is good enough baseline that you could live with. Still, I went after its response to matching to our preference better and the sound improved by a good notch or two:
I arbitrary dialed in that sub-bass EQ. It worked well enough to bring out that region without changing the overall impression of bass or making the headphone boomy. I put in a shelving filter to pull the highs down and that worked well. I think brought down the resonance around 4.3 kHz and compensated with pulling up the 2 kHz.
Once there, the transformation was impressive. Spatial effects were reasonable before but now were incredibly satisfying. It felt like you had your head inside a medium sized dull house with an orchestra playing! I wish I still had the Sennheiser HD800S with me to compare. From memory though, I think the HE-6 is close if not the same as its magical response in this regard. I am assuming the large cups and spacing from the ear is responsible for this open sound.
With equalization, I really had no other wishes for this headphone. It was comfortable and produced incredible fidelity. Everything was there from clean bass to detail and resolution. And oh, I was driving it with Topping A90 which could drive it quite loud on high gain. I also tested it on RME ADI-2 DAC V2 and it too managed to drive it. So no, you don't need a power (speaker) amplifier to drive it. High performance amplifiers I have been recommending can mange it.
I liked the sound of HE-6 so much that while working on the review, I was playing my selection of music with it and constantly saying, "wow, that sounds good!"
Conclusions
It is a shame this headphone is discontinued and was expensive to boot. Objectively the performance is quite good with distortion being a stand-out in addition to good amount of bass out of box. With four filters, the sound is transformed not only tonally, but also from imagine/spatial qualities, differentiating from other headphones.
I am going to put the HE-6 four-screw version on my recommended list. With EQ, it lands in my "highly recommended" bucket. Will be sad to let this go.
FYI, I have asked the owner to chime in and explain exactly what it is that I tested.
He also lent me some other mods but I have not tried to assess them.
------------
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 HE-6 has a serious look to it and beefy metal parts:
I think the wiring provided are aftermarket.
The large cups allowed it to instantly fit on my head with excellent comfort despite its above average weight.
The cup is round and its inside diameter is 60 millimeters. The depth is 18 millimeters.
Note: The measurements you are about to see are preformed using standardized GRAS 45CA headphone measurement fixture. Headphone measurements require more interpretation than speaker tests and have more of a requirement for subjective testing as a result. In addition, comparison of measurements between different people performing it using different configurations requires fair bit of skill. So don't look for matching results. Focus on high level picture. Listening tests are performed using RME ADI-2 DAC and its headphone output.
Mounting the headphone on my test fixture was challenging, resulting in quite a lot of variation between channels and overall response. I optimized this as best as I could but like there are some error in low frequencies.
Hifiman HE-6 Measurements
Before I show the measurement let me state that this was the easiest headphone to measure by far. I just put it on my test rig and it instantly registered equal levels in both cups. And furthermore, the level barely changed when I switched to a low frequency of 80 Hz. It was a joy in this regard!
Let's start with frequency response of HE-6 and comparison to our preference target to figure out tonality of the headphone:
Now you see what I meant by ease of measurements. See how the response is ruler flat and matching in both cups from 20 Hz to almost 1.5 kHz! I have never seen such precision before. Yes, our preferred response asks for more bass but this is a great baseline to have instead of drooping, or jagged response. Someone had a target of flat response there and got it! Beyond 1 kHz, we have some shortfall from target followed by excessive peaking and exaggerated highs. Neither is very extreme though:
Check out the distortion levels:
At 94 and 104 dB, there is essentially no distortion from 20 Hz to 10 kHz! 114 dBSPL brings out some unhappiness between 1 and 2 kHz. We can see that there must be multiple sound sources from the group delay:
Low frequency response though is textbook accurate with that sloping down graph. Again, I don't recall seeing another headphone that clean in that region.
Back to distortion, the HE-6 passes my 40 dBSPL threshold with flying colors:
The HE-6 has a reputation for being very inefficient, needing ton of power and we can see that in my testing:
It is in a class by itself there.
Typical of planar magnetic transducers, impedance is flat and low:
Hifiman HE-6 Listening Tests
I remember testing the HE-6 a couple of weeks ago for another purpose and saying, "hey, this is not bad!" Same impression held this time around. The sound is very clean with just a bit of high frequency exaggeration. What bass there is, is good enough baseline that you could live with. Still, I went after its response to matching to our preference better and the sound improved by a good notch or two:
I arbitrary dialed in that sub-bass EQ. It worked well enough to bring out that region without changing the overall impression of bass or making the headphone boomy. I put in a shelving filter to pull the highs down and that worked well. I think brought down the resonance around 4.3 kHz and compensated with pulling up the 2 kHz.
Once there, the transformation was impressive. Spatial effects were reasonable before but now were incredibly satisfying. It felt like you had your head inside a medium sized dull house with an orchestra playing! I wish I still had the Sennheiser HD800S with me to compare. From memory though, I think the HE-6 is close if not the same as its magical response in this regard. I am assuming the large cups and spacing from the ear is responsible for this open sound.
With equalization, I really had no other wishes for this headphone. It was comfortable and produced incredible fidelity. Everything was there from clean bass to detail and resolution. And oh, I was driving it with Topping A90 which could drive it quite loud on high gain. I also tested it on RME ADI-2 DAC V2 and it too managed to drive it. So no, you don't need a power (speaker) amplifier to drive it. High performance amplifiers I have been recommending can mange it.
I liked the sound of HE-6 so much that while working on the review, I was playing my selection of music with it and constantly saying, "wow, that sounds good!"
Conclusions
It is a shame this headphone is discontinued and was expensive to boot. Objectively the performance is quite good with distortion being a stand-out in addition to good amount of bass out of box. With four filters, the sound is transformed not only tonally, but also from imagine/spatial qualities, differentiating from other headphones.
I am going to put the HE-6 four-screw version on my recommended list. With EQ, it lands in my "highly recommended" bucket. Will be sad to let this go.
FYI, I have asked the owner to chime in and explain exactly what it is that I tested.
He also lent me some other mods but I have not tried to assess them.------------
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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