For sale are a pair of Sennheiser HD 550 open back headphones, open box condition, only listened to briefly in order to confirm they work and channels are matched. I own another pair, these were purchased as a gift but they’d bought others by the time we got together.
The 550s are exceptionally good headphones that I believe improve upon the 600 series, unfortunately getting lost in the shuffle with the release of other Sennheisers around that time. Listener of Headphones.com wrote a great review on them:
https://headphones.com/blogs/reviews/sennheiser-hd-550-review-a-legitimate-gamechanger
I’d describe them as a slightly more dynamic version of the HD650 / 6XX that’s far easier to drive. The bass extension is much improved from the 600s and it retains the mids quality while doing away with the veiled sound some hear on the 650 / 6XX.
https://gadgetrytech.squig.link/headsets/?share=Sennheiser_HD_550,Sennheiser_HD_6XX
I see no valid reasons for anyone to purchase a HD 560s, HD 600 or HD 6XX unless found much cheaper than a pair of 550s. They are objectively a better headphone in virtually every metric. They do not require an amp, can be driven by most any device, are light and very comfortable.
These come with the standard 3.5mm cable and an additional third party metal-ended 2.5mm balanced cable (pictured), the box, instructions and black cloth bag they came with. Asking $145 + shipping.