If you want to know what mine are a clone of, I'll tell you what my inspirations were to make what I have:
1. My Beyerdynamic DT-990 Pros plugged into my Schiit Vali is as good as it gets to me so far. That sounds great and is extremely comfortable. I love the way Beyer's grey velour feels, their earcups are a nice size to me, and their pad designs excellent. I didn't want to tear one of those apart as they even cost too much broken to do this to, but it's designed so well as to be an excellent platform. I took apart a cup doing my detachable cable mod to them, and I was impressed with how serviceable it is. The Superlux HD-330 is a copy and is cheap enough to rip apart. I had to do considerable reworking of metal pieces to make it fit like a real Beyer.
2. I saw how Martin Logan builds speakers on How It's Made. I'm sorry in advance if I'm about to step on toes. They showed their process well enough for a a tabletop copy of how they make speakers translates to a passable headphone driver. They actually have huge precision, which is the harder part, but their design shows how to make an electrostatic driver simply and cheaply. It's so elegant in its simplicity that I don't understand why that isn't for sale everywhere so the price can come down. They've made it good, safe, and easy to have,
3. Acquiring enough bits and pieces of actual equipment to use stuff that's safe and flexible. That means having weird watches in eBay for stuff from Koss or Stax. Basically tracking down LKQ (Like Kind & Quality) of plastic film, figuring out what to coat with since Swash isn't a common brand here, etc. I've got stuff to make it work, but I still definitely want a pair of the real thing.