*Edit* Due to requests, I will add my impression of the Stax SR-507 as well. I used a SRM-1 Mk2 C to power it.
Just thought it might be nice to have a thread comparing the two headphones du jour ... the HiFiMAN HE-6 and Audeze LCD-2. I'll go first with my impressions...
Just as a background, I've owned a few high-end headphones (see my profile) and heard every top headphone except the HE-90, Qualia, and Edition 10. My references for natural, neutral sound are the Beyerdynamic DT-48e and Stax SR-507, both of which I owned. In my system I use a Sony DVD player for transport, Cary Audio Xciter DAC, Violectric V100 amplifier, and Audioquest cables (I just like the way they look
). The V100 can put over 2 watts continuous power into 50 ohms, so it's more powerful than most headamps.
Build Quality
LCD-2
This is a very nicely built headphone with one major flaw: the ear cup swivel mechanism. Without tightening the adjustment screw, the ear cups swivel freely around every time you take off the headphone. The height adjustment is also very loose in the state the headphone comes from Audeze. The ear cups flopping around all the time is super annoying, but not a major issue. Aside from that, my pair was built very well. The wood looks fantastic. It's not plasticized wood such as you will find on Denon headphones...the Audeze's wood ear cups are more like a fine piece of furniture than the dashboard on a 1985 Cadillac. It's a nice headphone to look at, but the adjustment mechanism is very annoying. Real leather earpads are a nice touch. The cable is very stiff, but looks quite nice.
HE-6
IF you owned a HE-5 LE, it's pretty much the same thing. For a small manufacturer, fit and finish is good. The adjustment mechanism is simple but works very well. The plastic ear cups and slider covers have a very dark purple finish, with the metal ear cup holder finished in purple metallic. While this may sound garish, in real life it looks quite nice. The whole line of HiFiMAN headphones use the same ear cups and slider mechanism, which is well built and nice to use. The ear pads and grille are easy for the user to replace, which also opens up the option of removing the damping under the pads or grille to change the sound of the headphone, something many HE-5LE users did. The braided cable looks great is is very flexible.
Comfort
These two headphones both have very large ear cups and will slide around if you move your head. That said, the ear pads of both are both soft and comfy. The LCD-2's mini-XLR cable connectors extend below the ear cups, often hitting my shoulders. The cable sheaths tend to stay in position once bent...they look nice but are not flexible. Comfort could be a deal-breaker with the LCD-2, so try before you buy.
Sound
LCD-2
The first thing you will notice about the LCD is bass. This headphone has the best quality bass I've ever heard in a headphone. The bass is very tight, extends very deep, and has great tonality. You can easily distinguish bass guitar with the LCD-2, wheras other headphones tend to bury it below other instruments. LIstening to a big band or jazz band with an acoustic bass, the LCD-2 will simply not be beaten. Where the HE-6 blurs bass notes together, you can hear the seperate pitches of each note with the LCD-2. The LCD-2s bass is very similar to the Stax SR-507, but a bit more prominent. In truth, the LCD-2's presents more bass than you would hear if you were present at the recording. But it presents the bass in a way that does not smother the mids. For me this is the "killer app" of the Audeze - if you love tight, tuneful bass nothing else will do what it can do.
For me there is one major problem with this headphone - a slight reverb that is very obvious with acoustic/classical music. This makes the music sound like it's being played in a very small room. The effect is similar to closed headphones. The LCD-2 is still quite enjoyable, but at this price point I will pick apart any small flaws. Tonality is OK, but not as realistic as the HE-6 or Stax headphones. Overall, the LCD-2 is slightly "dark," but this doesn't bother me. Attack and decay are incredibly quick - this is NOT a slow, heavy headphone. The treble is well-articulated, but treble tonality is poor compared to the HE-6. The LCD-2 makes all cymbals sound a bit mechanical - on the HE-6 they sparkle organically. Detail retrieval seems equal to the HE-6. If the reverb doesn't bother you, then you will appreciate the LCD-2's speed, balance, and incredible bass. This is a nice headphone that can play every genre and shines with jazz, bluegrass, and big band.
HE-6
Caveat Emptor: You need a VERY powerful amplifier. I play to buy a speaker amp ASAP. For those who plan on running it with a headphone amplifier, consider a very powerful amp such as the Violectric V100, Beta22, or Eddie Current designs. In my opinion, anything under 2 watts is not really gonna get you there. If you can take care of that requirement, you will find the HE-6 is a balanced, tonally accurate, exciting headphone with just one real flaw. The bass and treble both have great extension. Compared to the LCD-2 the bass is more muted and it's harder to distinguish individual bass notes. The HE-6 reverses the situation with treble: its treble shines and sparkles realistically when the Audeze gives you dull tones. The SR-507's treble is a bit more clear than the HE-6's, but outside of stats you won't find better treble reproduction. The HE-6 has incredible tonality that matches real instruments better than any other headphone I've heard. Bass, mids, and treble are all well-balanced. Some have reported the mids are a bit forward - perhaps this is so, but it's not a Grado by any means. The only real flaw is poor soundstaging. For whatever reason, instruments are presented slightly out of place. On recordings that image a certain way with every headphone I've ever owned, the HE-6 presents the instruments in different places. The effect is much more prominent with studio-recorded rock music than single-miked classical. So you might get your guitars and drums in places you are not expecting. Other than that, there's not too much wrong with the HiFiMAN.
*bonus round* SR-507
I prefer this headphone to both of the planars. It has many strengths and no weaknesses. It may not stand out in any one area, but it's better balanced than the LCD-2 or HE-6. Provided that you have an electrostatic amplifier, I highly recommend buying it. Compared to the previous generation lambdas, there is much more bass quantity (the quality was already excellent). Many people thought the SR-303/404 were bass-light. Well, I doubt anybody will think that about the 507. The bass is not as prominent as the LCD-2, though. Instead, it's at a realistic level and well-balanced with the mids and highs. Tonality is quite realistic. The treble is very clearly delineated. If there is only one word to describe this headphone, it would be "effortless." The 507 will play the most complicated music easily. That is just the nature of electrostatic transducers. Soundstaging is also excellent and much better than either of the planars. To my ears the sound sig was a tad dark, but nothing like the LCD-2. Others did not find the 507 dark at all. Overall it's well-balanced, realistic, and incredibly fast. If you can swing an electrostatic setup, I would go for it. The Stax amps are too heavy for me to take to China and I was interested in trying the planars, so I switched. But if I had to live with one for the rest of my life, it would be the 507.
For me, the winner is the HiFiMAN HE-6. I prefer it's natural tonality over the LCD-2's unrealistic echo effect and dull tonality. But your mileage may vary, depending on your priorities. Both are "good" headphones for sure, if not quite as good as the best electrostats. If you don't have a super powerful headamp, you would be better served with the LCD-2.
Just thought it might be nice to have a thread comparing the two headphones du jour ... the HiFiMAN HE-6 and Audeze LCD-2. I'll go first with my impressions...
Just as a background, I've owned a few high-end headphones (see my profile) and heard every top headphone except the HE-90, Qualia, and Edition 10. My references for natural, neutral sound are the Beyerdynamic DT-48e and Stax SR-507, both of which I owned. In my system I use a Sony DVD player for transport, Cary Audio Xciter DAC, Violectric V100 amplifier, and Audioquest cables (I just like the way they look

Build Quality
LCD-2
This is a very nicely built headphone with one major flaw: the ear cup swivel mechanism. Without tightening the adjustment screw, the ear cups swivel freely around every time you take off the headphone. The height adjustment is also very loose in the state the headphone comes from Audeze. The ear cups flopping around all the time is super annoying, but not a major issue. Aside from that, my pair was built very well. The wood looks fantastic. It's not plasticized wood such as you will find on Denon headphones...the Audeze's wood ear cups are more like a fine piece of furniture than the dashboard on a 1985 Cadillac. It's a nice headphone to look at, but the adjustment mechanism is very annoying. Real leather earpads are a nice touch. The cable is very stiff, but looks quite nice.
HE-6
IF you owned a HE-5 LE, it's pretty much the same thing. For a small manufacturer, fit and finish is good. The adjustment mechanism is simple but works very well. The plastic ear cups and slider covers have a very dark purple finish, with the metal ear cup holder finished in purple metallic. While this may sound garish, in real life it looks quite nice. The whole line of HiFiMAN headphones use the same ear cups and slider mechanism, which is well built and nice to use. The ear pads and grille are easy for the user to replace, which also opens up the option of removing the damping under the pads or grille to change the sound of the headphone, something many HE-5LE users did. The braided cable looks great is is very flexible.
Comfort
These two headphones both have very large ear cups and will slide around if you move your head. That said, the ear pads of both are both soft and comfy. The LCD-2's mini-XLR cable connectors extend below the ear cups, often hitting my shoulders. The cable sheaths tend to stay in position once bent...they look nice but are not flexible. Comfort could be a deal-breaker with the LCD-2, so try before you buy.
Sound
LCD-2
The first thing you will notice about the LCD is bass. This headphone has the best quality bass I've ever heard in a headphone. The bass is very tight, extends very deep, and has great tonality. You can easily distinguish bass guitar with the LCD-2, wheras other headphones tend to bury it below other instruments. LIstening to a big band or jazz band with an acoustic bass, the LCD-2 will simply not be beaten. Where the HE-6 blurs bass notes together, you can hear the seperate pitches of each note with the LCD-2. The LCD-2s bass is very similar to the Stax SR-507, but a bit more prominent. In truth, the LCD-2's presents more bass than you would hear if you were present at the recording. But it presents the bass in a way that does not smother the mids. For me this is the "killer app" of the Audeze - if you love tight, tuneful bass nothing else will do what it can do.
For me there is one major problem with this headphone - a slight reverb that is very obvious with acoustic/classical music. This makes the music sound like it's being played in a very small room. The effect is similar to closed headphones. The LCD-2 is still quite enjoyable, but at this price point I will pick apart any small flaws. Tonality is OK, but not as realistic as the HE-6 or Stax headphones. Overall, the LCD-2 is slightly "dark," but this doesn't bother me. Attack and decay are incredibly quick - this is NOT a slow, heavy headphone. The treble is well-articulated, but treble tonality is poor compared to the HE-6. The LCD-2 makes all cymbals sound a bit mechanical - on the HE-6 they sparkle organically. Detail retrieval seems equal to the HE-6. If the reverb doesn't bother you, then you will appreciate the LCD-2's speed, balance, and incredible bass. This is a nice headphone that can play every genre and shines with jazz, bluegrass, and big band.
HE-6
Caveat Emptor: You need a VERY powerful amplifier. I play to buy a speaker amp ASAP. For those who plan on running it with a headphone amplifier, consider a very powerful amp such as the Violectric V100, Beta22, or Eddie Current designs. In my opinion, anything under 2 watts is not really gonna get you there. If you can take care of that requirement, you will find the HE-6 is a balanced, tonally accurate, exciting headphone with just one real flaw. The bass and treble both have great extension. Compared to the LCD-2 the bass is more muted and it's harder to distinguish individual bass notes. The HE-6 reverses the situation with treble: its treble shines and sparkles realistically when the Audeze gives you dull tones. The SR-507's treble is a bit more clear than the HE-6's, but outside of stats you won't find better treble reproduction. The HE-6 has incredible tonality that matches real instruments better than any other headphone I've heard. Bass, mids, and treble are all well-balanced. Some have reported the mids are a bit forward - perhaps this is so, but it's not a Grado by any means. The only real flaw is poor soundstaging. For whatever reason, instruments are presented slightly out of place. On recordings that image a certain way with every headphone I've ever owned, the HE-6 presents the instruments in different places. The effect is much more prominent with studio-recorded rock music than single-miked classical. So you might get your guitars and drums in places you are not expecting. Other than that, there's not too much wrong with the HiFiMAN.
*bonus round* SR-507
I prefer this headphone to both of the planars. It has many strengths and no weaknesses. It may not stand out in any one area, but it's better balanced than the LCD-2 or HE-6. Provided that you have an electrostatic amplifier, I highly recommend buying it. Compared to the previous generation lambdas, there is much more bass quantity (the quality was already excellent). Many people thought the SR-303/404 were bass-light. Well, I doubt anybody will think that about the 507. The bass is not as prominent as the LCD-2, though. Instead, it's at a realistic level and well-balanced with the mids and highs. Tonality is quite realistic. The treble is very clearly delineated. If there is only one word to describe this headphone, it would be "effortless." The 507 will play the most complicated music easily. That is just the nature of electrostatic transducers. Soundstaging is also excellent and much better than either of the planars. To my ears the sound sig was a tad dark, but nothing like the LCD-2. Others did not find the 507 dark at all. Overall it's well-balanced, realistic, and incredibly fast. If you can swing an electrostatic setup, I would go for it. The Stax amps are too heavy for me to take to China and I was interested in trying the planars, so I switched. But if I had to live with one for the rest of my life, it would be the 507.
For me, the winner is the HiFiMAN HE-6. I prefer it's natural tonality over the LCD-2's unrealistic echo effect and dull tonality. But your mileage may vary, depending on your priorities. Both are "good" headphones for sure, if not quite as good as the best electrostats. If you don't have a super powerful headamp, you would be better served with the LCD-2.