Solutions

The accuracy of CAL's steering enables system designers to provide directed coverage even when mounting options in a venue do not allow physically aiming the loudspeaker to the desired coverage area. Multiple or split beams can be used as needed. For example, a split beam can be used to avoid sound hitting a reflective balcony surface.

Because CAL is oriented toward vocal reproduction, very high intelligibility was a requirement. Reducing reverberation through pattern control is of little consequence if audiences still can't understand what's being said. Studies have shown that phase coherence at frequencies as high as 10 kHz is important to intelligibility, in contrast to the long-held belief that bandwidth up to 4 kHz was sufficient. CAL has been engineered to maintain accurate beam steering up to 10 kHz to ensure greater intelligibility in critical speech applications.

CAL is also uniquely capable of controlling high-frequency grating lobes (areas of undesired acoustic energy produced outside of the intended coverage beam), which are created by a spatial aliasing effect when drivers are more than a half wavelength apart. CAL is the only column loudspeaker that incorporates both extremely tight HF driver spacing (about 3/4") plus discrete amplification and processing for each driver. The result is virtual elimination of grating lobes below 10 kHz along with precise beam formation and uniform coverage.

These predictions show a CAL 96 with a split beam configuration to avoid placing energy on the balcony face while still covering all seats. The top portion of the beam is steered at a 17° uptilt, and the lower beam is steered at a 9° downtilt, to cover the main floor-level seating area.
2.0kHz	2.5kHz	3.2kHz	4.0kHz

5° Vertical Beam, steered at 0°	10° Vertical Beam, steered at 0°	5° Vertical Beam, steered at 15° downtilt	10° Vertical Beam, steered at 15° downtilt	2.0kHz 2.5kHz 3.2kHz 4.0kHz

Real-World Uses for Advanced CAL Technology

CAL's adjustable beam height and steering allow flexible installation options without compromising speech intelligibility. Cabinets may be placed higher up, as normally preferred for aesthetics, security, and free pedestrian transit. At the same time, the sound can be precisely steered to target pedestrian level while avoiding hard surfaces, thus minimizing destructive reflections.

To maintain the design motif of U.C. Berkeley Memorial Stadium (modeled after Rome's Coliseum), the 38 CAL 96 loudspeakers here are installed on poles. With precise beam steering, coverage is aimed into the seating to attain maximum throw distance and crisp intelligibility. Potential problems with bleed into adjacent residential neighborhoods are eliminated.

CAL Q&A

John McMahon
CAL Column Array Loudspeaker

Second Life for Hamer Hall