Pros: Outstanding sound at a price that is very attractive in the realm of high end headphones
Cons: Requires a very powerful partnering amp to get the best out of them.
Now that I have spent time comparing the HE-6, LCD-2, Edition 10, T1, and HD800, I thought the time was right to put down a few thoughts on the HE-6, which are, when properly amped, a TERRIFIC headphone.
The HE-6 have incredibly transparency, and a very wide-bandwidth delivery that is remarkably even and smooth. While they have just a slightly lively treble, this is more an elevation overall than a single peak, and their treble performance sets them apart from the HD800 and Edition 10, which have more issues in the treble. The bass is just slightly less in weight and quality than the LCD-2, but nonetheless outstanding. And the mids are just unbelievably transparent.
While the HE-6 can sound phenomenal, they won't unless they have a lot of power. The best they ever sounded to me was hooked up to the speaker outputs of my Leben CS300XS, which is a 15 wpc amp. There is no doubt that the HE-6 like a good strong amp. But given good, plentiful power, they well deliver an amazing sonic performance for the money.
To elaborate on the amplification story - the fairly low efficiency really does mean a pretty powerful amp is needed to make them come alive. The WA6 was insufficient. The Leben CS300XS was better (from its headphone out), but the Decware Mini-Torri was even better (since using its headphone out is basically 100% the same as using its speaker outs). Via the Decware, the HE-6 can really be allowed to swing, and swing they do. I later tried driving the HE-6 from the SPEAKER outs of the Leben, and this was better still. This gave the HE-6 a better sense of ease and dynamics.
Even later, I used a vintage Marantz 75 wpc Receiver for the HE-6, and this was also excellent. Much better than any of my other headphone amps except the Leben and Decware, which are really speaker amps themselves. A speaker amp really is the best choice for the HE-6, and you can get a pretty good one without spending huge amounts of money.
I spent some VERY enjoyable time with the HE-6 played via the Fisher KX-100. For those unfamiliar, the KX-100 is a 60's vintage all tube integrated amp using 7868 pentode power tubes in a push-pull, transformer coupled configuration, and with speakers rated about 25 wpc. The headphone Jack is driven off the output transformer, presumably using a 32 ohm secondary winding, but I am not sure of that.The Fisher is has a classic tube sound - warm, romantic, and lush, with a plump bass and a slightly shelved down treble, with beautiful sounding mids. This works better with some headphones than others, but it was awesome with the HE-6, which are, on their own, very neutral, with just a slight treble tilt. The combination was just gorgeous - surely not the most neutral sound there is, but wonderful to listen to.Power wise it was fine. On the Fisher's own scale of 1-10, I got my normal listening level at 6.5, which is where I typically listen to speakers on the Fisher (which I use primarily as a speaker amp). The results were highly enjoyable.
I also tried the Meier Concerto. At reasonable levels, the Concerto sounded very, very good with the HE-6. I also spent some time today with the HE-6 and an inexpensive Class D speaker/headphone amp, which outputs 10W into 8 ohms, and the Concerto was so much better with the HE-6 that it was almost laughable. I stopped listening to the Class D amp after about 20 minutes. It really did not sound good, and just slightly above my normal listening levels, it started to distort badly.
For whatever reason, the Concerto does not ever distort. I get to full rotation of the volume control, in high gain mode, and there is no distortion or clipping, and that is a level quite a bit louder than I would normally listen at, although I know from experience that it is a lower level than some people like (although those people are taking chances with hearing damage).
So since there was not a problem with clipping or distortion, I tried to listen for other more subtle signs of stress, which at my normal listening levels, I really could not detect. Overall the sound was quite engaging, smooth, and nicely nuanced. I got nice punch in the bass, and very natural mids, with less glare in the treble than I have heard with some other amps that I know were straining. The treble was actually really nice in combination.
I definitely would not recommend that people who own the HE-6 buy a Concerto to use as the main amp for them, as there is no doubt a limit to the Concerto's ability to drive them. But if your main amp was already a Concerto, and you wanted to get HE-6's with the idea of using them with the Concerto to drive them at least for some not insignificant period of time, I wouldn't hold back. The combination was certainly serviceable - it was actually quite enjoyable, within its volume limitations. But the HE-6 definitely sound much better with more power than this, and will reward the listener with even better sound with more power.
So as you can see, while I preferred some really powerful amps, the HE-6 are a superb headphone even driven by some pretty "normal" headphone amps. And how much power you really need is also highly dependent on what kind of listening levels you want to achieve. I realized once again when a friend of mine was over that I listen to headphones at much lower levels than many people do. The last two people who have come over here to check out headphones listened at levels I personally couldn't stand. So how much power you need absolutely depends on how much volume you're going to demand.
Of all of the current production high-end headphones I own, only the LCD-2 slightly nudges out the HE-6 overall for me, although for someone who likes a little more treble energy, I am certain they would prefer the HE-6. And for me the HE-6 are still terrifically good, when powered right. An impressive headphone.
It's funny - when I got the Beyer T1's, I was thrilled - they were so much better than any of the other headphones I owned. But then along came the LCD-2, and now the HE-6, and my T1's are not getting very much head time. The HE-6 are better than the T1, IMO. They are more open sounding, and seem to put less in between the music and the listener than the T1, which is a good thing.
But in any case, the HE-6 have been really impressive. With the right amp, they have are highly transparent, have great dynamic capability, and a very wideband neutrality. I can tell they will be a staple of my collection for a long time to come.