Headphones and Earphones
- Written by Stephen Hornbrook
- Published on 27 August 2012
Introduction to the HiFiMAN HE-6 Planar Headphones and EF-6 Headphone Amplifier
After reviewing a true bargain in the planar magnetic headphone market, the excellent sounding and easily driven HiFiMAN HE-400 (link to review), I moved onto their top of the line HiFiMAN HE-6. An intricately hand-made product, the HE-6 makes no compromises in its approach to high-end headphone design. Once unpacked I set out to see what makes the HE-6 such a good headphone and what it takes to let them truly sing.
The HE-6 is a planar magnetic design and its drivers use an extremely thin film of Mylar that has <1µ of gold deposited by vacuum evaporation to create the conductive pattern which is then aligned with an array of magnets. This thin film (76mm x 76mm) is what vibrates in order to produce sound. The use of gold allows for the very thin layer which is good for sonic performance, but has the drawback of being not the greatest conductor. This then leads to a less efficient, harder to drive headphone. As this is the best solution from a pure sonic standpoint, the drawback can be overcome with the use of a powerful dedicated headphone amplifier. Born out of this thought, the EF-6 is hand-built out of steel and aluminum and weighs a hefty 24 pounds. It can output 5 watts of pure Class A power and is more than capable of delivering the HE-6's to their full sonic potential.
HIFIMAN HE-6 PLANAR HEADPHONES AND EF-6 HEADPHONE AMPLIFIER SPECIFICATIONS
- HE-6 Planar Headphones
- Sensitivity: 83.5 DB
- MFR: 8 Hz - 65 kHz
- Impedance: 50 Ohms
- Weight: 1 Pound
- MSRP: $1,299 USD
- EF-6 Headphone Amplifier
- Output: 4 Watts Pure Class A into 50 Ohms
- THD+N: 0.03%
- S/N: 95 dB
- Power Supply Design: CLC filter
- Dimensions: 4" H x 12" W x 13" D
- Weight: 24 Pounds
- MSRP: $1,599 USD
- Secrets Tags: Headphones, Earphones, Earbuds, HiFiMAN
Design of the HiFiMAN HE-6 Planar Headphones and EF-6 Headphone Amplifier
The construction of the EF-6 is more along the lines of a high quality power amplifier than a headphone amp. The faceplate is black with a brushed texture on the inside and glossy outer section, creating a nice frame around the sturdy 24-step volume attenuator. The attenuator is large, heavy and provides a satisfying click with each adjustment. Silver brushed aluminum buttons are used for the power and input selection. Also up front is a mini-jack input for quick access with a portable device. For more permanent connections there are two pairs of gold RCA inputs on the rear. One pair of RCA outputs is also included on the rear in order to use the EF-6 as a pre-amp. The only other control on the rear besides AC power is a small toggle for two gain settings: none and -10db.
The build quality on the HE-6 is equally impressive. They feel more robust and solid than most headphones I have used. The ear pads are soft and comfortable and conducive to extended listening sessions. The outer shells of the mini planar magnetic speakers are painted a glossy black with hints of dark purple in the right light. The head size adjustment feels stiff and grips enough to support the extra weight of these headphones. Connecting these headphones to the EF-6 is a detachable OCC (single crystal copper) 4pin XLR cable along with an optional OCC XLR to 6.5mm headphone plug adapter for amps without a 4-pin XLR plug. My only critique would be the small twist on connectors to the headphones. They can be a bit of a struggle to screw on. For input sources I connected the analog outputs of an Oppo BDP-95 to one input and a Clearaudio Concept turntable via Pro-Ject Phono Box to the other.
On the comfort scale, I rate the HE-6 headphones near the top. Yes they are heavy, but the weight is evenly distributed across the plush headband so they don't feel like you hung giant speakers over your head. They are snug, but don't pinch the top of my ears by being overly constrictive and the ear pads are soft and luxurious while maintaining some breathability. Being an open-air design, not much outside sound is kept out. It is best to be alone in a quiet room to truly enjoy these cans.
Listening to headphones is about as intimate an experience you can have with your music, aside from being alone in a room with your favorite musicians. I found my time with the HE-6/EF-6 combo to be an illuminating experience. I tend to listen to headphones at work while multitasking, where the music takes second place. Seldom do I have the time to sit down in a room and do nothing but listen to headphones. When you get to this level of quality that is all you want to do. Perhaps a nip of scotch and some light reading, but that's it.
Overall, the HE-6 have a very full and satisfying sound to them. Bass extension is terrific with plenty of definition and the right amount of presence. The high end is not too bright and never feels fatiguing. They are easily a headphone I can listen to all day long. The soundstage is the largest I have experienced with headphones, where the music encapsulated space well beyond my head feeling open and airy.
Radiohead's In Rainbows sounds terrific on the HE-6/EF-6. Not having to deal with speaker cabinet resonance or room acoustics means achieving flat bass response should be much easier on a headphone. While there are plenty of headphones without flat bass response, the HE-6 is not one of them. They produce the cleanest bass response on this album to date, along with great low-end extension. You don't feel it quite like you do with full range speakers, but it is the closest headphones have come to a full-body experience. Thom Yorke's voice is presented a bit forward and is full without being throaty or shallow and empty. Having the HE-6 powered by the EF-6 provides great dynamics that feel limitless. You will never have to worry about not having enough power with the EF-6.
On Joni Mitchell's Both Sides Now, the strings are delicate and wispy in the background, and her smokey voice is upfront and never too bright. When the sax comes in it feels dynamic and unrestrained, thanks to the hefty EF-6.
Edward Sharpe and the Magnetic Zero's latest album, Here, on my Clearaudio Concept has wonderful layers of sound with a full presentation. The background chorus is presented as it should be: in the background. The HE6's ability to deliver detailed midrange comes through here in Edward's voice and the delicate acoustic guitars.
When listening to Miles Davis Kind of Blue, I experience a soundstage that I find wider than what a headphone should be capable of. You get so much dimensionality with the HE-6 that musicians don't just claim a space from left to right, but from back to forward. To me this is one of the holy grails of high-end audio. I want the sound to have body, anchored in a virtual space, where it is easy for my brain to imagine the artist performing. Of course this would be worthless if the quality of the sound the virtual instruments were playing was not convincing. Certainly, this is not the case with the HE-6. I hear clean hi-hat cymbals from drummer Jimmy Cobb and a terrific ring to Miles Davis's trumpet. When Adderley and Coltrane on alto and tenor start playing, the sound just takes me away. There is plenty of life to the music and the presentation is transparent - an audiophile term I hear thrown around all the time but here was the perfect example of where nothing came between me and the music.
This is a review that I did not want to end. I feel a better connection to my music collection from a pair of headphones than ever before. HiFiMAN is making some excellent high-end gear and as a centerpiece, the HE-6/EF-6 does the job well. This is not a cheap system, retailing for $2898, but the prices are well in-line with similar competition and not everyone has room for full-range speakers, amps, pre-amps, and source components. I highly recommend giving this pair a look if you are in the market for the ultimate personal audio system.
HiFiMAN HE-6 Planar Headphones and EF-6 Headphone Amplifier On The Bench
For testing the EF-6 amplifier, a set of AKG K701 headphones was used for the test load. As they are a very demanding load that requires a dedicated amplifier to get any bass out of them, they push the amplifier as hard as almost any non-electrostatic headphones will.
On the 1 kHz test tone the 2nd and 3rd harmonics are both very low, giving us over 80 dB of headroom and a low noise floor that has a slight right starting around 45 kHz. The main issue seen is a 60 Hz tone which seems to indicate some noise from the power supply getting into the signal.
With a 10 kHz tone we see very similar results, with close to 80 dB of room above the 2nd harmonic though once again that 60 Hz tone is there around 70 dB below the fundamental tone.
The 19 kHz and 20 kHz IMD test shows that the sidebands are 70 dB below the primary tones and drop off quickly. There is also a peak at 31 kHz that is present in all the other charts as well. It is low and likely not audible at all, but still present.
With the 60 Hz + 7000 Hz IMD test, the 60Hz spike from the power supply isn't an issue since it has a tone there as well. We once again have over 80 dB of headroom here, and a pretty low IMD number for an amp being driven to this level.
If we zoom in very close on the frequency response we see there is a very slight rise in output from 20 Hz to 20,000 Hz, but no more than 1 dB across the whole range, and then a slight roll-off after it peaks at 45 kHz, before a steep fall off after 80 kHz.
Across the whole frequency range the THD+N measures in at right around 0.07%.
I did run some additional testing with lower power loads and less demanding loads from headphones on the EF-6 and this caused improvements in all measurements across the board, allowing me to reach the 95 dB of SNR that HiFiMan has specified. These tests indicate something close to a worst case scenario, and show that the EF-6 has good performance across the board even then.