When discussing the "worst" headphones I've heard, I have to take this to mean "for the price" or "given expectations I had before listening." Otherwise I could list any number of boring cheap earbuds that sound like garbage. In any case, here's my list (controversial, no doubt):
1. Ultrasone Edition 8
I've never had much luck with Ultrasones, and these were no exception. People usually would consider these to be Ultrasone's best, and I would agree -- but to me, they still sounded like a glorified Bose Triport. Sure, the bass was tighter, and the treble was clearer, but ultimately the sound signature was very similar. Moreover, the Bose headphones were much more comfortable. For the price of the Edition 8, it was a big disappointment.
2. Audio Technica ATH-W1000X
These were reviewed positively by many people, and several seemed to prefer these to the Denon Dx000 headphones. To me, they just sounded extremely unnatural. Mids had a nasal quality, midbass was somewhat bloated and obscured the mids. Another disappointment.
3. Audez'e LCD-2 (Rev. 1)
I think that these may have been the most hyped headphones in Head-Fi history. In the early stages, when only a few people had these headphones and they were in short supply, they were getting extremely rave reviews -- so many were calling them the best headphones they'd ever heard. The measurements were also very impressive. Because of all the hype, it made these even more disappointing when I got them. To me, it sounded like listening to an orchestra that was crammed into a closet -- absolutely no soundstage, with no sense of air or space. Tonal balance was overly warm for my taste too, with bass overwhelming the other parts of the spectrum. Since I had these, I've heard the LCD-2 Rev. 2 and the LCD-3 in meet conditions, and to my ears the same problems still prevail. Not my cup of tea.
4. Ultrasone Edition 10
I only heard these in meet conditions, but 15 seconds of listening was enough to tell me that I wanted no part of these headphones. They sounded very poor and unnatural, especially considering the exorbitant price tag. Based on the sound I heard, I might pay $100 for these, at most -- though I prefer the sound of my Grado SR-60i.
On the flip side, headphones that I thought sounded good for the price, or met expectations, included the Sennheiser HD800, Beyerdynamic T1, Beyerdynamic DT880/600, and the Sony MDR-R10. I also liked the AKG K701 -- though they don't quite sound natural, their sound signature lends itself very well to acoustic guitar.
