I stole this off somewhere else: "Not sure why but there's fabric pouches inside each earcup containing a simple LC filter consisting of an electrolytic cap bypassed by a film cap in parallel with a 471uh inductor. Tried removing it and the sound is more open and a little brighter without. First time I've seen a tuning circuit consisting of through hole parts inside a production headphone." Sounds like hardware EQ. Would love to see some frequency graphs with and without the lc at some point.