If you are looking at this Ad you know how good these headphones are. If not then please see the following youtube video where they have been reviewed. In UK these headphones cost £695.
The HE-500 is one of HiFiMAN's best performing planar magnetic designs yet its 89dB sensitivity is higher than similar designs and allows it to be driven with a conventional headphone amplifier. The HE-500 offers impressive frequency response from 50Hz to 50KHz and with all of the dynamics and lifelike realism that HiFiMAN headphones are famous for.HE-500 headphones are much higher efficiency than HE-6. Customers can use regular headphone amplifiers to drive HE-500.
Frequency Response: 15 to 50 KHz
Impedance: 38 Ohm
Efficiency: 89 DB
Weight: 502 g
Leather storage box
Silver headphone cable (3 meters or 10 Feet)
leather earpad 1 pair (on the headphones), velour earpad 1 pair for backup
headphone cable connector*2