These headphones are amazing. The clarity of sound and the response to input is just impossible. These headphones do sub bass very, extremely well. The only thing is you need to supply a lot of power to bass. Here is crazy setup I use for EDM (e.g. Paul Oakenfold). Note that I would never use such crazy setup for any other music genre (maybe it's also good for metal, haven't tried yet).
Here is the setup (keep in ming it's crazy an has not much to do with flat or pure)
Laptop -> TOSLINK -> NAD T744 -> PMA500AE -> HD215
NAD set to no effects and no tone, and Denon (that's going to be good one) I set Loudness ON and Bass to MAX, Treble to mid. Listening to Paul Oackenfold, and the experience is exactly as I were there - LIVE screw EVENT!!!! Sub bass is so powerful. These headphones can do as much bass as much current you can provide. I right now feel like I had two sub-woofers attached to my ears. Brain is cooking!
Denon is set to 9o'clock and NAD to -8dB