I'm having the same probelm. I can confirm that Archive.org *does* support byte-range requests but you have to follow the redirect first.
curl -I -r 200-300 https://archive.org/download/CarlosKillpackRants/Rant%201%20-%20Music%20and%20Ec onomic%20Deacy.mp3
HTTP/1.1 302 Moved Temporarily
Server: nginx/1.1.19
Date: Sun, 01 Sep 2013 20:44:23 GMT
Content-Type: text/html; charset=UTF-8
Connection: keep-alive
X-Powered-By: PHP/5.3.10-1ubuntu3.2
Accept-Ranges: bytes
Location: https://ia601002.us.archive.org/29/items/CarlosKillpackRants/Rant%201%20-%20Musi c%20and%20Economic%20Democracy.mp3
curl -I -r 200-300 https://ia601002.us.archive.org/29/items/CarlosKillpackRants/Rant%201%20-%20Musi c%20and%20Economic%20Democracy.mp3
HTTP/1.1 206 Partial Content
Server: nginx/1.1.19
Date: Sun, 01 Sep 2013 20:45:35 GMT
Content-Type: audio/mpeg
Content-Length: 101
Last-Modified: Thu, 29 Aug 2013 08:00:23 GMT
Connection: keep-alive
Expires: Mon, 02 Sep 2013 02:45:35 GMT
Cache-Control: max-age=21600
Content-Range: bytes 200-300/12725312
I suppose you could use the direct urls..
