HE-6 (4 screw)

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NO SMOOTHING is applied to the shown plots. Most measurement sites have some smoothing applied which ‘irons flat’ sharp peaks and ‘wiggles’. I do not use smoothing because some info about sound quality is lost when plots are smoothed.

Aside from a small correction of the microphone itself also some correction in the lowest frequencies is applied to the plots to compensate for the perceived loss of bass when using headphones. This is described HERE in more detail.
A ‘horizontal‘ frequency response curve on the shown frequency response plots on this website thus indicates a perceived ‘flat’ tonal signature.

ALL measurements are made with a good SEAL on a flatbed measurement rig.
The shape of your head, bone structure, pad size, pad ‘softness,  (compliance), hair or no hair and or wearing glasses may (drastically) change the frequency response of some headphones, so… your personal experience may differ substantially from these plots.

Frequency response (tonal balance) is the most sound-determining aspect of headphones. A horizontal line shows audible neutral response in the plots on this website. Deviations in different severities at different frequency bands have an effect on the sound character.
The bigger the deviation the stronger the effect.

Below an aid to help determining the sound character of headphones with relation to the frequency response.

sound descriptions mine

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HIFIMAN HE-6

HE-06

 

The HIFIMAN HE-6 (4 screw version) is an orthodynamic over-ear headphone intended to be driven directly from desktop equipment or the output from a speaker amplifier.
It retailed for around € 1300.- which is quite a lot of money for a headphone back in the day it came out but since then surpassed by many other ‘flagship’ headphones.
This is the 4-screw version, the first version (which was made from 2010 to 2012).
The later 6-screw version was less bright sounding and considered by many to be lesser sounding than this 4-screw version.
I can’t find any data about the years of production but figure they were produced till around 2015.
These headphones are very inefficient. To get a good and dynamic sound you need a headphone amplifier that can deliver a few Watt in 50Ω or a loudspeaker power amplifier.
A power amplifier that can deliver 30W into 8Ω or 60W into 4Ω will be able to power this headphone quite well and to decent SPL levels.
Of course those power amps will not ‘deliver’ that power but will deliver about 5W in that case.

This headphone came with the original leather pads. The velours pads were not included.
This headphone is quite heavy in weight which may bother some people when having a long listening session. Also the leather pads become slightly sweaty and warm after a while.
Long listening sessions are quite likely though as the sound quality is excellent !

The SMC connectors are a bit fiddly and one has to be careful when putting these down.
These connectors aren’t exactly made for this purpose (small form HF connector).

specifications:

Type: Over ear, open
Usage: Home.
Driver type: orthodynamic
Pads: replaceable,  leather
Collapsable: No, but can rotate the cups in a flat position.
Headphone connector: SMC connector
Cable entry: double sided
Cable: replaceable, 2m with 4-pin XLR connector (male)
+ 1m with 4-pin XLR socket and 6.3mm TRS jack.
Driver size: 60 mm
Nom. power rating: not specified
Max. S.P.L.  not specified but around 5W
Impedance: 50 Ω
Efficiency: 77 dB/1mW (90dB/1V)
as measured by Tyll but specs claim 83 dB/1mW.
Weight: 502 g.
Clamping force: low/medium
Accessories: XLR to 6.3mm TRS,  extra velour pads, high quality presentation box for transport.

Sound description:

Well, this headphone doesn’t disappoint when connected to an amplifier that can deliver enough power. You don’t have to try to drive it from your phone or wimpy C’Moy amp.
You will only get a soft sound that starts to distort at low levels.
With a decent amp (used an Ember and a power amp) this headphone comes alive and sounds full and detailed and very realistic. Bass is well extended and not exaggerated.
Mids are very clear. The top end is slightly too high on poorer recordings but sounds very good on well recorded material.

measurements:

Below the frequency response of the HE-6 (Left, Right)HE6 FR

The channel balance is quite good, certainly for a used 8 year old headphone.  The tonal balance is ‘flat’ as in neutral. Maybe a tiny bit less pronounced in ‘body’. Mids are ‘loose’ and ‘forward’ sounding with good detail and presence.
The treble is very high quality, perhaps a tiny bit ((a few dB) elevated around 10kHz which ‘enhances’ the details slightly. Extension is great. 30kHz at 0dB so no roll-off till at least 30kHz. There are slight differences between L and R driver between 1kHz and 5kHz but could not hear this at all.
This is one of the better measuring headphones I have come across when it comes to tonal balance.

The HE-6 is no longer available but has been ‘replaced’ by the Susvara.
This headphone will be measured later on…. I hope.
The Susvara, however, is a LOT more expensive but is lighter in weight.

It would be fair to compare the HE-6 to the HE-1000 and perhaps the Edition-X.
Of course, the Ed-X can be driven directly from a phone and weighs a lot less and is more comfortable. The HE1000 is a closer competitor but is much more efficient and lighter in weight as well.

Below the frequency response of the HE-6 compared to the HE1000 and Edition-X with some slight smoothing applied to the plots.

HE flagships

The tonal balance differences become a bit more clear when 1/3 octave smoothing is applied. The plot below shows this quite well. HE-6, HE1000 and Edition-X.
tonal balance flagships

Below the distortion measurements of the HE-6 (Right channel).

DIST HE6 R

Most of the time the left and right channel measure closely the same which makes it pointless to show both channels. In this case however the left and right driver behave differently. Below the Left channel.

DIST HE6-L

The distortion levels are quite low, most certainly in the bass.
Below the same measurement but shown in percentages instead of dB distance.
Below the Right channel:

DIST HE6-R percent

and Left channel below:
DIST HE6-L percent

These are excellent results. The left channel has higher amounts of 3rd order distortion compared to the Right channel but doesn’t exceed 0.2% which is still very good.

 

output resistance / damping-factor

As this is an orthodynamic headphone its impedance is as good as ruler flat so a higher output resistance amplifier will have no consequences for the frequency response/tonal balance/damping.

Below the CSD (Waterfall plot) of the HE-6. (Left and Right channel are superimposed)
HE6 CSD
This plot shows excellent behavior from 500Hz to 2kHz. Better than most headphones I have measured. There is some ringing (probably caused by tension of the membrane) which differs between Left and Right channel. Maybe due to age, maybe it was there from day one… no way to tell.
The left channel rings at a lower frequency (3.5kHz) and the right channel around 4.5kHz.

Below the spectrum plot of the HE-6 (Right channel)
Spectr HE6 R

Below the spectrum plot of the Left channel.

Spectr HE6 L

These plots show the Left channel has some ringing issues around 3kHz and 7.5kHz.
Bass to mids looks really nice. The Right channel shows less ringing and in a different frequency range 4 – 5kHz.
I don’t think that this will be that audible as in that frequency range our ear canals ring anyway.

The step response (Right channel) below shows the sub-bass is just very slightly rolled-off. The resonances (around 4.5kHz) are short lived and not very high in amplitude.  Impulse response is at the proper level and shows excellent qualities with a only a slight emphasis in the upper treble. It thus sounds very clear and articulated and smooth. You can still see some medium frequency wiggles in a low amplitude on the horizontal trace which shows the lingering discussed above around 4-5kHz.
The trace running quite horizontal is evidence of the excellent mids, bass and subbass performance.
HE6 step R

Below the step response of the Left channel.
HE6 step L

The absolute phase of this headphone is turned 180 degrees compared to all other headphones I measured. This is something others also had noticed.
This absolute phase difference is not audible so not really and issue but strange non the less.
This only shows up when looking at square-wave and impulse plots.
For this reason I ‘doctored’ the 100us impulse plot a bit by flipping the measured trace around the horizontal axis so the plot looks like the other ones on this website.
100us impulse corrected
The impulse is nice and sharp and of the proper amplitude. Impulse response is pretty good. The low frequency ringing is at around 900Hz and also visible in the spectrum plots. The amplitude is relatively low (-15dB) and dies out quickly.

 

summary

The HE-6 is still an excellent sounding (very realistic and detailed with good bass) headphone. Even compared to newer and much more expensive flagships of today.
It requires (MUST be) driven from a capable amplifier. This means a headphone amp should be able to deliver at least 2W in 50Ω or be driven by a speaker amp. 30W into 8Ω or 60W into 4Ω.
When these conditions are met and you aren’t bothered by the weight this is a great sounding headphone. Maybe one of the greatest even till today.

 

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