An industry-wide objective of the early 1980's was the goal of delivering big sound from small speakers.
Conventional three-piece systems of the time struggled to meet this goal, but rarely delivered on the promise. The sound often came at a price, with a subwoofer that often produced audible distortion limiting its placement options.
Dedicated research and design by Bose engineers led the way with a revolutionary idea, later to be known as Acoustimass® speaker technology: a system that delivers room-filling sound without the compromises of conventional solutions.
Challenge
For years, conventional speakers needed to be big in order to give listeners full, rich sound. As a result, those speakers became the unsightly centrepiece of most listening areas. An early approach to this problem was to split the two large speakers into three separate pieces: one large subwoofer for low frequencies, and two smaller speakers for mid and high-frequency sound. Ideally, you would only see the smaller speakers and the subwoofer could somehow be tucked out of sight.
The idea was valid but, due to the nature of conventional speaker design, another problem arose: Drivers in the subwoofer would often distort due to inefficiency, creating a localizable range of sound. While this is less noticeable in a two-piece system, when a conventionally designed subwoofer produced the same audible distortion, listeners could pinpoint its location, ruining the stereo effect.
Localization meant the subwoofer had to be placed between the two smaller high-frequency speakers, making it clearly visible and defeating the intended benefit of a versatile, three-piece speaker system. The original problem didn't go away. You just went from two large visible speakers to one large visible subwoofer.
Bose engineers took a different approach to solving these problems. The result was the revolutionary Acoustimass speaker technology.
Solution
When a conventional approach to three-piece systems produced the additional problem of localizable distortion, Bose® engineers set out on a research path to deliver rich sound from a small system. They found that by encasing the bass drivers inside a specially engineered module, low-frequency sound could be launched into the room on a column of air.
Low-frequency speaker drivers were placed between separate acoustic compression chambers inside the module. As each speaker cone moved, it excited air in the chambers. The air trapped in the chambers interacted with air in the ports, to produce more low-frequency sound with greater efficiency.
This system, to be known as Acoustimass speaker technology, proved to be more efficient, required less cone motion and produced less distortion. If any audible distortion was produced, the patented design trapped it inside the acoustic chambers — so it never entered the room.
The result of this innovative approach to speaker design was an Acoustimass module that could be placed virtually anywhere, with a technology that allowed for truly small speakers.
Through years of additional research, Bose engineers have continued to improve and build upon this technology, delivering unique solutions for a variety of challenging applications.
Learning Applied
Since 1987, Bose engineers have continued to refine and improve on Acoustimass® technology to meet the needs of new and more demanding methods of entertainment.
As home theatre has grown in popularity, this proven technology has met the challenge. The original problem of large speakers is multiplied with a home theater system. Instead of requiring just two stereo speakers, a home theater generally requires five or even six speakers in order to recreate the excitement of surround sound. Bose Virtually Invisible™ speakers combine with the latest version of our Acoustimass modules to create fuller, richer sound without a room full of bulky speakers.
The latest version of the Acoustimass speaker systems incorporates the proprietary acoustic loading technology that terminates in a large area port and ensures high output levels with a relatively small amount of cone motion (see illustration).
Limiting the amount of cone motion greatly reduces the level of adverse audible artifacts, this allows the module to remain non-localizable and to be placed almost anywhere within the listening environment.
The new version has a much larger exit (port) area that allows the module to play deeper – cleanly – at higher output levels than other typical designs.
The Acoustimass module is capable of reproducing a much wider range of frequencies, thus allowing it to reproduce everything from the deep bass of a typical subwoofer to the lower mid-range of frequencies. It is thus the only bass source necessary to use in conjunction with the cube speakers and allows them to be very small and elegant without compromising overall acoustic performance.
This innovative technology isn't limited to just home entertainment needs. Acoustimass speaker technology has been adapted throughout a wide variety of other Bose applications.
Versions appear in a number of our professional products for both live music and business music applications. Performance halls demand the rich, deep lows on an expanded scale. Small businesses benefit from the ability to hide the Acoustimass module away from customers.
As music and even movies are taken on the road, Bose automotive music systems have used Acoustimass technology where the expectation of full sound meets the demands of limited space. The same principles of problem solving continue to be applied wherever the need for quality sound arises.
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