Why don't we start posting graphs from all the CD players and sources with a flat FR in the audible range? Stereophile has enough of them! How about the professional audio equipment that is used to record the music we love? Professional audio equipment is designed to be "flat." If it isn't the manufacturer will tell you, or it is some equipment that is designed to change the FR.
Providing graphs of "High End" CD players with rolloffs in the audible range only provides me of evidence of one thing - that some high priced eqiupment is not made properly or has been specifically designed to change the sound. The goal of audio equipment is, typically, to transmit a signal in a transparent manner. There is some equipment is that designed to specifically change the FR like an EQ, but then I know the changes are there or I make the changes to my liking.
Nankai - Rather than coming here and defending this, why don't you ask HiFiman to address this? Even a $20 Cmoy has a flat FR. Then you won't have to defend the product to anybody.