Hi guys/gals! I have done additional listening and ...
1. I measured the output of both the prototype and the production units using a Radio Shack dB meter model 33-2055. The production HE6 is about 2-3 dB louder with the same song, amp, cables, and same volume setting.
2. Although I liked the sound of the HE6 prototype there was something that did not quite click with me. Now that I have listened to both side by side I know why. The prototype unit has a "veil like" presentation which is not in the production HE6.
3. The production HE6 has a crystal clear presentation, yet I hear no harshness nor any shrillness. Instead I hear a very smooth presentation that is very appealing and engaging, basically I want to continue listening and not put the production HE6 down.
I can only think of three other dynamic headphones that are in the same category, the AKG K1000, the Sony Qualia, and a MarkL modded Denon w/ his V4 wood cups. I realize many would be shocked at my inclusion of the Denons and that I have not included the Sennheiser HD800 nor the Sony R10. Well I prefer the first three and not the later two.
I have not listened to the LCD-2 so I can not comment on them. I have also not compared them w/ any of the Stax offerings choosing to keep the comparison with dynamic headphones. Cheers.