Subjective listening is one thing, measurement is another. It is very difficult to notice channel disbalance unless it's too extreme and even then you absolutely need to listen to a particular set with familiar reference content while directly comparing with the other set in question. Otherwise it will be as you say "close enough". I am sure all the modders pay close attention to matching their drivers but big manufacturers is the whole another story. There you have a low pay girls trying to get more production volume and probably an engineer whose only job is to pick perfect pairs for reviewers.

Can't speak for the 400i (though Marv's measurements look kinda...meh), but the PM2 and AD are completely different. The AD is quite bassy, though tunable, and fairly neutral otherwise with a bit of glare to the sound. The PM2 has flatter bass, but it can be a bit weak, ethereal, or "limp-dick" sounding. The PM-2 is overall more laid-back and perhaps more natural sounding than the AD, but I also found it to have its own sort of rough quality to the treble that may or may not annoy some (likely just my ears). And it does have some noticeable information "missing" in the upper mids and treble.

Personally, I think the HD600 and HD650 are better than either of the two. More balanced overall.

You might also be interested in my upcoming ZMFxVibro review. My review has been delayed quite a few times, but things are in progress between Zach and me. The ZMFxVibro has a bass boost not unlike the AD but with an overall slightly darker and certainly more organic response. It also has tunable bass, though not to the extent of the AD. Once you dial that in how you like it, I found the ZMFxVibro to be a more enjoyable listen than the AD or PM2...maybe even preferred over the Senns as well. Still have listening and tests to do...we'll see. So far I find them encouraging.

I dunno if it's just my pair, my ears, or what, but my Mad Dog 3.2 is pretty peaky and sharp in the treble (not sure about Pro, which might incorporate the new dot and felt tweaks). Not exactly what I'd call relaxing or laid back. I got used to it early and never noticed until comparing with other headphones later on, plus my ears have gotten better since then. I have since had to apply front damping in order to listen to my MD comfortably. (My pair was 3.0 when you measured them, I believe.)

PM1 or PM2 with PM1 pads are pretty darn laid-back...hit some good spots for me, though were sometimes too boring. But, seriously, if you're looking for AD but more organic, bit more lush, and more laid-back, do consider the ZMFxVibro as well. I'll be resuming the tour fairly soon and encourage established members to give them a shot...just gotta take care of some things and get a full review in, hoping to do so within a week.

Haven't heard the LCD2 but would really like to some day.

I would consider headphones other than HE-400i if what you want is relaxo laid back. Maybe HD650, Paradox Slant, Mad Dogs, PM2 (maybe with PM1 pads), LCD2.2. I'd be happy to give you a succinct comparo summary of those five headphones if you would like.

Curious about the Slant. Have had the 2.2 and the 400. For rock, I have read that the Mad Dogs and Alpha Dogs sound lean. So what say you?