Questions about DIY Headphones, speaker drivers, homemade earcups

I know headphone drivers are extremely hard to buy. Where do you think I can find some cheap dynamic drivers that have relatively good specs? Do you know of speaker drivers that have a rather flat frequency response that are suitable for use in headphones? How about tweeters? I don't think they extend low enough.

Is there any real difference between headphone and small speaker drivers? Can speaker drivers sound as good as headphone drivers in the same setting?

What material would be best to be used to make earcups? What sort of plastic? Any other cheap ways of moulding apart from a cheap 3D printer?

I couldn't find much information myself, as I'm thinking about building it from the ground up or nothing less than some heavy modding on existing generic headphones. Any advice that could let me translate what I have in mind to a physical object would be great. Thank you.

For the first few prototypes, it's really down to cheap drivers, drivers from cheap but good headphones (KSC-75,etc) or decent tiny speaker drivers.

Parts-Express has a minimum order amount of $50 for Australia. Something like this from mouser costs $35 in shipping. I'm probably better off with something like KSC-75 for drivers.

Too bad earmuff don't usually have round cups, otherwise I would turn them into something rather good. I just remember there are some DIY moulding videos on youtube from guys like the indymogul. Maybe it'd be the most economical choice for me.

I don't suppose there are cheap but nice headbands for full size cans around either, hey? I can get some cheapo headphones from Dino Direct for around $6 for example, but those headbands don't look that great.

Not sure what you mean. I saw the mod costs $400. I don't suppose the drivers can be anything but expensive.

I created a WTB thread asking for used headphone drivers anybody would like to get rid of. PM me or leave a comment if any one of you has something like that.