Mirage Omni 250 Surround Speaker System In All Directions
Neither bipole nor dipole speakers are truly omnidirectional, though a bipole is arguably a closer approximation. The holy grail of omnidirectionality—and the only truly omnidirectional speaker—is the proverbial pulsating sphere (or, even better, an infinitely small, pulsating point source) generating a flat frequency response in every direction. No one has fully achieved this, and even were it possible, there is no universal agreement that this would constitute the perfect speaker. While most sound radiation in the real world is multidirectional, that doesn't necessarily mean that it's correct to reproduce sound omnidirectionally.
Almost everyone agrees that an ideal speaker shouldn't reproduce sound like a laser beam. It should, instead, produce a uniform response over a reasonably wide area, but whether that area should be a 30° forward angle, a 60° wedge, a fully omnidirectional pattern, or something entirely different remains an open question. And while everyone agrees that the wider a speaker's dispersion pattern, the more the room influences the sound above the bass region (in the bass, the room always strongly influences the sound), whether or not the benefits of ultrawide dispersion outweigh the disadvantages is still in dispute. At the moment, the linear-response-over-a-narrow-front-facing-wedge faction is winning. But attempts to produce the ideal omnidirectional speaker continue, and its adherents are often passionate.
Back in the Happy Days of "hi-fi," when a fledgling format called the stereo LP was generating all the buzz and "home theater" was the high school drama club rehearsing Our Town in your living room, audio pioneer Stu Hegeman was building speakers with tulip-shaped tweeters radiating in all directions. Infinity marketed speakers in the '70s using a related design, though Infinity's driver looked more like an ice cream cone.
Hegeman inspired others, including Richard Shahinian, who designed the classic Citation 13 for Harman/Kardon in the early '70s, then went on to found his own speaker company, Shahinian Acoustics, where he pushes the omnidirectional envelope to this day. Ohm, dbx, JVC, and Design Acoustics have also made notable omni- or multidirectional speakers, and mbl still does. A number of manufacturers also produce speakers with at least some rear radiation, particularly in the high frequencies.
Last but not least is Amar Bose, whose 901, a "direct/reflecting" variation of the omnidirectional concept, launched the company that bears his name and has now been in continuous production, with periodic updates, for almost 35 years. What few will remember is that Dr. Bose first designed and marketed a speaker called the 2201: an eighth of a globe with 22 identical drivers and designed to sit in a corner where, reinforced by wall reflections, it would (it was hoped) simulate that elusive, pulsating sphere.—TJN