The pair of SRH840s I received are optimized for studio recording and critical listening with reference-quality frequency response, rich bass, clear mid-range, and extended highs. They have 40mm neodymium drivers that are closed-back for good isolation in the studio--musicians need to block out the sound of the rest of players or their own loud instrument or guitar amp in the case of a loud guitar player.

The phones are lightweight and super comfortable with big cushy pads that seal well against the sides of your head. An extra set of ear cup cushions is included with each pair--thoughtful, as the cushions are the first things to get trashed. I also liked the phones collapsible design and the adjustable hand band with graduated markings for exactly resetting their fit every time you use them.

I compared the 840s to my pair of AKG K271s. I plugged them both into my Aphex Model 454 HeadPod headphone amp. The HeadPod has four separate and identical amplifiers.

The AKGs are exceedingly flat and clinical sounding in the sense they do not put any "love" on the sound. I suppose, for purposes of evaluating the audio quality of my recordings and mixes, this might be preferred. However during recording sessions, I like the artists and musicians to emotionally react to the music euphonically and not analytically. When given the choice, my singers and musicians prefer the Shure SRH840s. I have to say that after the evaluation process of listening to performances and mixes on the AKGs, I switched over to the 840s--they revealed much about the sound and mix but are more fun to listen on.

Other features are: a bayonet clip securely locks the 3M (10ft) replaceable coil cord cable into the ear cup; a big carrying bag; gold-plated plugs at both ends of the cable with a threaded 1/4-inch adapter; 44-ohm impedance (they are louder than my AKGs); 1-watt power handling capability; and a 5Hz to 25kHz response with 102 dB/mW sensitivity rating.