Sennheiser IS-850
Little is documented about the Sennheiser IS-850. No production years or original price have survived in the archive's records, and Sennheiser's own literature for the model is scarce. What we do have are two period reviews, and they agree on the essentials: this was a mid-1990s wireless headphone system that used an infrared light beam rather than RF to carry the audio signal.
Audio ran an Equipment Profile in May 1995 (p.68) and found the system worked well with a range of sources, including portable CD players, all of which provided more than adequate output. The separate S 850 transmitter could be set on a shelf using its supplied metal base. In measurements (p.69), the response extended to about 17 kHz before falling gently toward 20 kHz; below 200 Hz it rolled off smoothly when there was no seal around the ear. On the listening side, the reviewer used "J'ai vu le loup," by the Baltimore Consort on La Rocque 'n' Roll (Dorian DOR 90177), as a test for acoustic space and voice articulation (p.76).
HI-Fi-Stereo-Buyers (Dec 1996, p.84) described the headphones as truly astro-looking, with overhead circuitry pods, battery pods, and four IR sensors at the crown, plus a thumbwheel volume control. Rated specifications quoted there included a frequency response of 10 Hz to 20 kHz with a 44.1 kHz sampling rate, and a signal-to-noise ratio of 101 dB with a digital input.
That is essentially the extent of the documented record. Enough to identify the IS-850 as a serious, reasonably ambitious IR headphone system of its era — but the finer details of its history, pricing, and lineup position remain unrecorded.
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