Disclaimer: This unit has been generously provided by my good friend, Danganronpa. And this is what I call a Southern hospitality, thank you very much! In order to minimize the linear error in the low frequency range, measurement has been carried out with acoustic leak minimized, by using a silicone putty as a sealant.
Although SR-207 is STAX's cheapest entry model, it is still a part of SR-Lambda series, which has a great heritage and legacy in the history of headphones. And since all of the current Lambda series models from SR-207 to SR-507 share very similar technical specifications, this entry model indeed deserves a good look as well.
CON: A slight channel mismatch above 1 kHz & inverted polarity. Again, a good acoustic seal is vital for sound reproduction below 100 Hz. It is such a shame that the cable is not replaceable.
an accurately calibrated microphone. The test result suggests that the entire surface of SR-207's diaphragm is not behaving uniformly just like any other Lambda series models, if not worse. The frequency response magnitude variation occurring at the polarized resonance frequency, 180 Hz, indicates the diaphragm's stiffness has been slightly increased from that of the classic models.