Ok, ok... Sound is personal, yes correct.
This post is coming from a guy with 2 floorstands with 6.5" woofers Xover @ 40Hz and 3 10" subs Xover @ 80Hz and no there is not a bump at the freq they overlap, actually they cancel out, perfect because there was a bump =D
Now, lets get down to business! AKG K702s characteristics in the low-end.
Starting with the actual frequency response, irrespective of SPL. This produces a biased view as almost every speaker goes down to 1Hz but you just can't hear it, or more realisticly, every speaker goes down to 30Hz but you can't hear it as it isn't loud enough; this isn't actually the case with the AKGs. The K702s can go down to 20Hz easily. I played some test tones and to not complicate matters lets assume the headphones didn't bleed into 25 or 30Hz and skew results, I could hear the headphones quite well. During this sweep from 1 - 100Hz I noticed many things, they are insanely flat, unlike my system that roars at the sub-40s and starts to shake the dry wall causing it to knock the support beams of the house at 100Hz (remember they start to cancel out around 40-80Hz) the headphones were flat and I respect that. Other if not all cheap systems will have no low-end and start to tear sh*t up around the 60-100 mark.
If we take an SPL vs. Frequency approach to this, the AKGs still do not lack any bass, as they were flat during this sweep. Of course, if we reveal the entire picture and not just a 1 - 100Hz sweep they are still flat... During a 1 - 48000Hz sweep that is ;)
To some real world tests, keeping in mind the SPL vs. Freq. Our ears are most sensetive to sound around 5,000Hz. This means that flat headphones are not flat to our ears, no, not flat at all. They will actually appear to "lack" mids and bass. They can also be fatiguing. Our ears also are not very sensetive to bass either, depending on the health of your ears you will not hear lows well and will require some extra power in that band. Remember as far as basic survival goes, it doesn't matter what the whale sings or how the elephant stomps there feet, neither does the bird chirps seriously matter, it is the human voice we need to hear, that is what we are sensetive to, our mothers own voice actually.
Therefore, I pronouce that "machine" flat headphones are not flat to us but to mics and test equipment that is not weighted to our ears.
Do the AKGs lack bass, no, they are being honest about what they get. What you feed them, they will put out. Will you hear the recording how the engineer heard it, no. I never understood that, if we get technical about it, each invdividual has different hearing and unless you are the engineer you will never hear it how he/ she heard it, so does honest reproduction really matter, well of course.
You still get to hear WHAT the engineer made correctly, mabye not how the engineer heard it. So, if you are looking for headphones, **** hear them first, the K702s may "lack" bass for your taste or they may have too much bass for your whale hearing ;)