Well I wouldn't even say that. He calls HD800 a facetweeter...
'tis true. I've updated my sig/profile to reflect that I do run Anax mods on the HD800 to tame the brightness and hard glare of the HD800. Even then, I still find it bright.
I do want to clarify that frequency response is only but one aspect; and even then, I do not find the PM-1's frequency response objectionable. To put things in perspective, I find the FR, particularly the treble, of Grados, SRH-1440, T1, etc. to be unbearable.
While I do prefer a neutralish response (by this I mean flat in the bass with a slow roll-off / slight downward tilt starting from 150Hz up to 20kHz where it's about -6db), I find that I can live with a wide latitude of tonal balance as long as there are not any sharp peaks in the upper midrange to lower-treble. The PM-1's overall tonal balance and lack of treble peaks easily meets my requirements, with two minor concerns that the upper midrange is too scooped out and the last octave is missing. Subjectively, the PM-1 is slightly too laid back, too polite, too forgiving. Keeping in mind that nothing is perfect, this is preferable to nasty treble peaks.
Where the PM-1 truly fails for me is not frequency response, but rather its subjective lack of clarity and resolving ability compared to other headphones of similar price. The PM-1 simply does not sound "hifi", and as I mentioned previously, it does not scale well with more capable upstream gear. This is typically indicative of high distortion over a crucial area of the audio band. The PM-1's "low-fi"-ish quality, for lack of a better term reminds me of the SRH-1840, but in much more limited way.
So I hear something. Now what I want to do next is confirm with objective data. So far we have two sets of measurements (ultrabike's and Brent's @about.com) indicating highish distortion > ~2-6% around 200-300Hz. Yes, these measurements are taken at 90db SPL which is extremely loud, but I have been able to correlate 90db SPL distortion tests with my subjective experience. I'm pretty confident in saying that distortion approaching 1% could be audible, and anything over 1% is definitely audible and probably deleterious (with certain exceptions - or understanding that distortion in the bass will be expected). Go going back to that distortion bump, I ask could that measurement anomaly account partially for what I am hearing? I can't be sure, but I believe it probably is.
Now let's compare to the PM-1 the HD650 subjectively. The sub-low bass of the PM-1 sounds better than the HD600. It's more controlled and less wooly. The midrange and treble of the PM-1, although muted compared to the HD650, sounds smoother and faster. However the fundamentals region of the PM-1 sounds like it has this veil, mud, lack of clarity, low quality feel to it. It's difficult to describe. The best way for me to say it is that it sounds like poo or goo.
Now it is possible that a lot of people will really like the PM-1? Of course! The PM-1 has many good qualities. But the PM-1 also has some poor qualities which happen to be showstopper issues for me. My intent was never to tell the current appreciators of the PM-1 that they had bad taste in headphones, but rather to inform people who are considering the PM-1 of the things it doesn't do so well, especially in comparison to other similarly or lower priced headphones available.
