In the late '70s and '80s, Bang & Olufsen had two audio products which offered well-above-par measurable performance, though there will doubtless be dissenters.
Bang & Olufsen turntables provided above-average isolation from acoustic feedback and very well configured tonearms which were (unfortunately) designed specifically for proprietary but very good B&O cartridges. In 1976, shortly after B&O launched its Model 4000 linear-tracking turntable, it was sued for alleged IP infringement on Harman/Kardon's linear-tracking technology, even though B&O's approach to a linear tracking mechanism was quite different than that used in the Harman/Kardon Rabco ST-7. The various B&O linear-tracking turntables were fairly reliable, and the mechanisms quite capable of handling the back-and-forth arm movement with minimal discernable tracking drift. In 1991, B&O abruptly canceled its turntable and cartridge manufacturing. Best turntables ever? Debatable, but they did elevate the standard of vinyl LP playback significantly above the median of turntables made during the mid-70s to late-80s era (though at a fairly hefty price premiuim).
Bang & Olufsen cassette decks (i.e. model 8000) were reviewed many times by objective reviewers like Julian Hirsch and High Fidelity (CBS Laboratories). Their cassette decks tested out with above-average performance, in terms of measured wow & flutter, speed accuracy, frequency response, distortion, and channel separation. Interestingly, to my recollection B&O never produced a three-head cassette decks, but their two-head decks were exceptionally effective, and most of them incorporated a very good automatic cassette bias/equalization/sensitivity calibration system for recording. Once again, though these decks were exceedingly good (highly regarded by the Tapeheads community), B&O definitely charged premium prices for its decks.
Speaking of recording, Bang & Olufsen improved upon the original Dolby HX headroom-extension system. In conjunction with Dolby Labs, most high fidelity cassette decks made from 1982 until 2014 obtained licenses to incorporate Dolby HX Professional. Dolby HX Pro enhanced the performance potential of most tape decks, providing a measurable reduction of harmonic distortion, particularly in critical upper frequencies. The Dolby HX Pro licensing scheme provided significant royalty income to Bang & Olufsen during the '80s and '90s.
So those are three areas where B&O made quite significant contributions to the state of the audio art.
