Maker independent
RAAL-requisite Ventura, California, USA (Requisite Audio) / eastern Serbia (RAAL manufacturing) · est. 2018 RAAL-requisite made the world's first full-range, pure-ribbon headphone (the open-baffle SR1a, debuted at RMAF 2018) and the first circumaural True Ribbon headphone (CA-1a) — a genuinely unique driver technology no other headphone maker uses, derived from RAAL's aluminum ribbon tweeters and handmade in Serbia.