Celebrity headphones are riding the crest of a wave at present, but the celebrity is often only hovering in the background. Most headphones are not the "Simon Cowell CX70s" or the "Sol by Deadmau5," and this is probably what has kept the genre becoming a second-hand celebrity perfume.
The Marshall Major 50 FX headphones are designed to celebrate Marshall's 50th anniversary, and here the "celebrity" is Marshall's famous amps, favored by rock legends including Jimi Hendrix, The Who's John Entwistle, Metallica's James Hetfield, or (my pick) Nigel "These go to eleven" Tufnel of Spinal Tap.
The limited-edition headphones are designed to look like Marshall amps with fine details such as a gold trim and a tweed-like grille on the drivers. The earcups are attached by a metal brace that gives the headphones an aviation headset look and are able to be folded inward for easy transportation. The earcups sit on the ear and are constructed of a leatherette material. While they were a little uncomfortable at first, with a quick bend of the "Marshall amp vinyl" headband they became much more wearable.
The 4-foot cord is one-sided, though unlike with the Bowers and Wilkins P3 headphones, it's not removable, and it features a three-switch microphone with universal start/stop and volume up/down for iOS devices. It's coiled at one end and can stretch up to twice its length, studio-headphones style.
To assist with portability, the headphones include a heavy cloth bag with a drawstring.
Apart from the cosmetics, the FX moniker also refers to a sonic upgrade on the standard Major headphones. The drivers inside are 40mm and offer a boost in bass response. I would never equate a guitar amp with high fidelity. For one, they're open, untuned boxes; second, they lack tweeters, which are the dedicated drivers that output high-frequency sound. But they're made for a different purpose and the Major 50 FXs manage to maintain the Marshall stamp while still sounding like full-range headphones.
Though bass guitarists -- such as the aforementioned John Entwistle -- have used the Marshall amplifiers for bass guitars, they are most often used for normal guitars, and this informs the Major 50 FX's sound.