Earlier in the year I went from a chair with a headrest, to a Steelcase Leap which doesn't have one, before ending up in an Aeron without the headrest. I can say it takes some getting used to. If you're in the chair strictly for work purposes during the day, I think you get used to it and you'll be fine. But if you're in the chair and sometimes like to sit back and watch something (or occasionally like to doze off in your chair like I do) then the headrest is necessary.
I went with the Atlas headrest. It's not cheap, but I think it's worth it. There's another one out there made by a company called "Engineering Now" that's a bit cheaper and has good reviews - but many of the long term reviews claimed it didn't hold its position well.
https://www.amazon.com/dp/B00L2IJNMK/ref=cm_sw_r_cp_apa_fabc_ihKZFb2D6722Y
I would love to have a set of Hi-Fi speakers on top of the Adams. They're great for near-field, but I do wish I had something else for sitting back and watching movies and whatnot. Have you heard the Adam A7Xs? If you have, how do they compare to your B&Ws?
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Yeah the LS50s are what I describe as a little polar. Some music (female vocals, mid-forward sounds like jazz and blues, etc.) are phenomenal and that's an understatement. The imaging, soundstage, etc. is perfect. However, when I listen to rock or electronic (or rap for you rap people out there), they fall quite flat and are very underwhelming. Essentially I found the KEFs were either a 10/10 or a 5/10. The Adams were a consistent 8.5/10 and for that reason I chose them over everything else.
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As for the Aeron, I'm using the Atlas Headrest: https://www.amazon.ca/gp/product/B00L2IJNMK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
For clarity, is this (not available) version the one you want?
https://smile.amazon.com/gp/product/B00L2IJNMK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
If so, yeah, the "Cushion" one is not the same shape. They still have images of the "butterfly" shaped one on their site, so maybe contact them directly to ask about it?
It's the Herman Miller Aeron. I got the headrest from Amazon link