@v10tdi

They have it regularly just check vie their interface.

I ordered one ages ago--still have not received it. Ordered early December, ETA end of March, but they did charge my card.

My Massdrop 6xx arrived today. Overall, it is what I expected. It is exactly the same as the HD650, with minor cosmetic differences. At $199, it is a very good deal. I slightly prefer the HD600, but the 650 is very refined. Compared to older Sennheisers like the HD580, the sound is very slightly veiled, or you could say that the older ones are a bit more open. Part of this may be due to the higher density foam in the earpads. Now, the foam in the older earpads was pretty soft, and had to be replaced fairly often, so maybe this is a good thing. There's a bunch of different modes you can do tto these cans but for now I am leaving them as is. They are nice looking. Band is a little tight but can be bend down at the metal ear connectors--don't bend the band itself or it will crack. The 1/8" (3.5mm) jack is made from heavy wire, I see no need to use a custom cable. An adapter is supplied. My serial number is above 30,000 so I guess they made quite a few of these.
Plusses: great sound, frequency response 10Hz-40kHz
Minus: Big, wasteful box looks classy but who needs a box for cans?

Active again on same URL

@DrDave

After many years I recommend X1 from JD for much cheaper $119

https://www.joybuy.com/3380027.html

As you'll get them you'll understand why and how HD600 are inferior.