In case some people unfamiliar with the 500's get the impression that they're fatally flawed in some way, it may be worth taking a read (in its entirety) of Tom Martin's review from 2011.
I think he does a good job of pointing out where the 500's deviate from the ideal - but also that this is a fundamentally well balanced headphone.
His conclusion:
"HiFiMAN’s HE-500 is a world-class headphone that provides almost all of the benefits high-end headphone listeners focused on accuracy could want. This is particularly true for listeners looking for a headphone that delivers much of what you would hear on an audiophile-grade stereo system. Listeners who want a headphone experience that differs from in-room audio by delivering maximum resolving power, however, may prefer headphones like HiFiMAN’s HE-6."
http://www.hifiplus.com/articles/hifiman-he-500-planar-magnetic-headphones-playback-47/
I think he does a good job of pointing out where the 500's deviate from the ideal - but also that this is a fundamentally well balanced headphone.
His conclusion:
"HiFiMAN’s HE-500 is a world-class headphone that provides almost all of the benefits high-end headphone listeners focused on accuracy could want. This is particularly true for listeners looking for a headphone that delivers much of what you would hear on an audiophile-grade stereo system. Listeners who want a headphone experience that differs from in-room audio by delivering maximum resolving power, however, may prefer headphones like HiFiMAN’s HE-6."
http://www.hifiplus.com/articles/hifiman-he-500-planar-magnetic-headphones-playback-47/