Portable headphone brightness, or the converse...

I've been walking around a lot with portable headphones and iPhone - the new Apple Earpods seem bright enough, but the v-moda M80, Beyer DTX501p, Harman/Kardon CL, Bose OE2, B&W P5 and P3, Sennheiser Amperior, Philips M1 and several others seem fairly dull in the treble.

After listening to any of these for several minutes, I take the headphone off of my head and listen to the live sounds around me, and the difference is startling! Everything I hear, from the occasional car passing, freeway sounds from 1/2 mile away, birds and other animals, people talking as they pass by - all sound very "live" with great detail and obvious high frequencies. But then I put the headphones on with various music tracks and it sounds quite dull. It isn't the iPod or iPhone that makes the dramatic difference, since comparing those devices with desktop systems feeding the Audioengine D1 and Dragonfly DAC/amps, or even the PA2V2 or FiiO E17 amps from the LOD show that the iPod and iPhone have essentially the same high frequency response from their headphone jacks as from these external amps. The dullness is occurring well below 10 khz, so the filtering of highs with MP3's above circa 17 or 18 khz isn't a factor in such dramatic dullness.

I wonder if anyone else has made similar comparisons using modern portable headphones.