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Innovations: Packing Power into a Portable PA—Bose F1 Flexible Array Loudspeaker System

Bose Professional is no stranger to changing the paradigm for portable PA systems.

Bose Professional is no stranger to changing the paradigm for portable PA systems. In 2003, we launched the L1 portable line array system, bringing a new way for musicians to connect more intimately with their audiences. The L1 served as PA and monitor combined, allowing performers to place it behind them on stage and mix their own music—a departure from the conventional “speaker-on-a-stick” format. This was possible by exercising a portable line array: fixed vertical coverage to keep sound off the ceiling, and a very wide (nearly 180 degree) horizontal spread to cover the stage and audience. The L1 line has been popular, especially with singer-songwriters and mobile DJs who value a system that sounds good, is easy-to-carry and quick to setup.

While the L1 bucked the system by putting a powered portable line-array in the hands of musicians, there were applications where the form-factor of a conventional PA was still needed. This problem bothered our engineering team, which pondered how enhanced system performance could be paired with coverage control. In looking at large-format concert touring systems that employ line-array shapes to cover different types of venues, the engineering team went to work on how to implement a similar approach into a portable, yet powerful product for the club stage. The F1 Bose Flexible Array Loudspeaker System was the result of that work.

Shape your Sound—The Bose F1 Model 812 Loudspeaker with FLEX Array technology has four modes conceived to provide the coverage needed for different types of venues. The F1 system consists of two parts: the F1 Model 812 flexible array loudspeaker and the F1 subwoofer. The F1 Model 812 consists of a 12-inch woofer-based, two-way, full-range system with a unique architecture featuring eight high-output Neodymium drivers on a flexible, horn-loaded baffle. The system is completed with the addition of a surprisingly portable companion subwoofer featuring two high excursion woofers that have the performance of a much larger-base box. Both components are powered and offer full-featured I/O panels and status indicators.

The team involved in the development of the F1 created a vision for the product by identifying customers’ practical and aesthetic needs. These included increased flexibility in directivity coverage, greater system portability and a more visually-appealing solution for speaker positioning and mounting. We also specifically wanted to address the tasks of improving usability and reducing set up and transportation challenges, while still ensuring customers can achieve clear, high-output, full-bandwidth audio for their audiences.

The first area of new proprietary IP (intellectual property) that the team deployed is the unique acoustic architecture that provides flexible vertical coverage. We identified some key, real-life coverage scenarios that we believe are not covered well by traditional portable PA product offerings. Raked seating poses challenges for good directivity coverage. Alternately, when an audience is seated below the stage, a stage-mounted system directs mid and high frequencies over the audience’s heads. The team utilized extensive acoustic modeling techniques to optimize the potential solutions before any prototypes were built and ultimately selected four vertical pattern coverage options as being the most helpful to users. These were: Straight; J-Array; Reversed-J and C-Array shapes. The new F1 system can be simply and intuitively configured to any of these coverage options by pushing on the top and/or bottom of the speaker front grille. The baffle array tilts and snaps into a place to configure to the desired option. These dispersion patterns have been achieved without employing a multi-cabinet hanging system.

The next key area where new IP was employed ensures that the F1 delivers consistent tonal balance for each array shape. The team created a control system that automatically changes the system EQ for each array shape. A built-in Hall effect sensor detects the selected array position and triggers a DSP to recall the proper compensation curve. Determining the appropriate EQ curve was based on multiple “in-coverage” measurement positions in a given room, and then repeated in multiple rooms, to generate suitable target curves. The final confirmation involved extensive critical listening, which was also performed in a variety of rooms, until we were comfortable with the results.

The unpleasant chore of hoisting conventional PA speakers on top of tripod stands was an experience that the engineering team was eager to improve upon. Our third area of IP applies to the design of the loudspeaker stand for the F1 system. The team (who are mostly gigging musicians) looked toward other methods for loudspeaker elevation that required less effort. The result was a stand that was stored in the subwoofer (critical to convenience), could be assembled quickly into the top of the subwoofer, and provided a surface area for mounting that is much easier to deploy compared to pole-mounting. The selection of a high-performance engineering- grade plastic resin was essential for us to achieve the durability requirements of systems that will be used and abused daily. Structural strength modeling was employed so that static and dynamic load requirements across a very wide operating temperature range would be met. To confirm, our test labs performed rigorous testing on the parts. The stand itself had a number of ambitious requirements for ease of use and functionality. We shaped it to achieve the appropriate mounting height as well as to manage and hide interconnecting cables.

Finally, the team set about extracting the optimum performance from the F1 subwoofer. This involved very careful attention to the design of both the system (enclosure, ports and amplifier), and a custom-designed 10-inch, high-excursion woofer. In this challenge, we needed to deliver the same volume velocity (cubic inches) as a subwoofer with a larger 18-inch diameter woofer. This requirement was achieved in drastically improved form factor that was proved crucial to delivering the “transportability” that the team had articulated in the product vision.

After a long process of identifying the needs of the user group, and setting goals for delivering significant and unique user benefits, the Bose development team is proud to introduce this system as an expansion to our portable products catalog. The result is our Bose F1 Model 812 Flexible Array Loudspeaker and F1 Subwoofer—the first powered portable loudspeaker designed to serve live music, DJ and general P.A. applications that lets users control its vertical coverage pattern.

Paul Fidlin serves Bose Professional as Director Of Engineering and Product Development

Bose Professional