Yea i'm not sure what that thing is either... the HIgher Number is... maybe an indication of performancs but I have no clue either
I pulled my HE-6 out of storage last weekend and reacquainted myself with its advantages (that bass, that midrange) and disadvantages (like clamping velvet-padded bricks to my head).
If the ergonomics on the new models are better, that alone can justify the price. The original assembly was plagued with problems which were eventually ironed out, but I suspect that Hifiman has been wanting something that's both less finicky to build and more robust in the user's hands. It looks like the cable sockets on the new models are at the 5:00 position rather than at the bottom of the headphone. That's good too.
Orthos are heavy because the driver is a thin metal-impregnated sheet of plastic moving within a strong magnetic field. The best way to get a strong magnetic field is to use massive sheets of magnets. This is why the flagship neo-orthos are so massive (well, that and the housing strong enough to keep massive sheets of magnets from ripping themselves from the mount).
The HE-400 was always Hifiman's lightest ortho because it only used a sheet of magnets on one side of the driver. I assume the new headphones are lighter because they're using fewer magnets that are more powerful. Although this would leave an opening for a yet-improved ortho that's just as heavy and uses the better magnets.
My own wishlist of improvements to the HE-6 would include ditching the SMC connectors for something easier to plug/unplug and more robust, and better internal wiring (what's in there now is circuit board jumper wire). You can get these as aftermarket mods, and though they're simple improvements they're not cheap since they require disassembling the phones and desoldering/resoldering the driver. We'll see what Fang comes up with at the top end of the range, I guess.
Edited by Mshenay - 1/9/14 at 7:22am