It may not be obvious, but the directionality of a sound reinforcement loudspeaker is as important a characteristic as its frequency response or power-handling capability. Control of "spill" is critical for sound reinforcement because the environments we deal with are almost always reverberant. If we cannot control the direction of sound, not only does it miss our audience, but it also does nasty things like bounce off walls, create comb filtering and decrease intelligibility. Traditionally, sound reinforcement loudspeakers have featured fixed directionality. In other words, the manufacturer designed the cabinet for a certain angle of coverage, such as 60º by 45º, and once you purchased the box, you were stuck with the dispersion pattern. For that reason, many sound companies need to purchase and stock loudspeakers that are identical except for their coverage attributes, requiring an investment in more cabinets as well as the space in which to store them. Several manufacturers offer molded horns that can be removed from their cabinets and turned 90º, allowing a modification of coverage from (for example) 60º by 90º to 90º by 60º for use in situations where you want to .swap. the vertical and horizontal coverage angles. This is a clever design feature that's useful when you need to change the horn's coverage, but don't have the ability to turn the box on its side (turning the box on its side is, of course, the poor man's way of modifying the dispersion pattern of a speaker). Unfortunately, removing, rotating and replacing the horn is time-consuming and not something you're likely to do on-site unless the P.A. is going into a fixed installation, and even with that, you'll only have two choices. What if you could quickly change the directional pattern of a loudspeaker without having to dismantle components, or without the need to change the orientation of the cabinet? Life would truly be easier and you could provide better sound in the process.
Sound reinforcement loudspeaker manufacturers recognize this quandary and are working on solutions. One of the most startling introductions at the October AES (and one of those hit-yourself-in-the-headbecause- it's-so-obvious developments) was a new loudspeaker called KUDO from L-ACOUSTICS, those wonderful folks who pioneered the line array and brought us V-DOSC. KUDO (K-Louver Modular Directivity United With DOSC Waveguide Technology) is a line-source array designed with two specific goals in mind: 1. To provide their Wavefront Sculpture Technology (WST) in both vertical and horizontal planes, and 2. To make this coverage adjustable to fit a wide range of applications. A medium-format three-way active system, the full-range KUDO cabinet incorporates two 12-inch, four five-inch and two one-inch drivers. The unique design aspect of KUDO is that each cabinet features L-ACOUSTICS' K-Louver technology (patent pending) incorporating two DOSC waveguides. The user can mechanically adjust the K-Louver, providing control over the coverage angle of the mid/high section (above 800Hz) and allowing the cabinet to easily be reconfigured with four different horizontal coverage pattern settings (50º, 110º, 80º left or right). Combined with the ability to orient the cabinet vertically or horizontally, these four settings yield a total of eight coverage options from a single cabinet. This versatility means that KUDO cabinets can quickly be optimized on-site to suit a specific venue, allows the array to be adapted for venues with odd physical characteristics and cuts down on the amount of inventory a sound company needs in order to accommodate a wide variety of coverage requirements.
Taking a completely different approach to manipulating loudspeaker directivity is Renkus-Heinz with their ICONYX digitallysteerable array technology. ICONYX employs Renkus-Heinz's IC series of loudspeakers designed to provide unobtrusive sound coverage under difficult acoustic circumstances. Primarily intended for speech and music reinforcement in houses of worship and transportation center P.A. systems, IC cabinets are modular columns comprised of eight full-range coax transducers and eight channels of Class D amplification developed specifically for the ICONYX system by D2 Audio (16-, 24- and 32-channel systems are available). Each amplifier channel incorporates DSP control over a single transducer via Renkus-Heinz's Windows-based LobeWare software. Manipulating the drivers via DSP, LobeWare lets the user adjust the beam's shape and directivity, even after the ICONYX array has been installed. If it turns out a column was hung too low, that column's acoustic center can be raised using software instead of by physically moving the array. The software also enables level and EQ modifications of up to eight IC columns after installation. I can already feel my back getting better.
A similar approach is taken by EAW with their DSA Series Digitally Steerable Array intended for use in small and mid-size permanent applications. Each driver in a column-shaped DSA loudspeaker has its own amplification and DSP controlled by EAW's DSA Pilot software. The software allows the user to vary the vertical coverage pattern from 15º to 120º as well as aim the coverage plus or minus 30º. The DSA draws technology from EAW's KF900 which employs Phased PointSource Technology™ (PPST). This technology was engineered to overcome the challenge of long-throw (more than 600 feet) sound reinforcement in which high frequencies become attenuated more quickly than lows. A truly long-throw system must have an extremely focused high-frequency section with very high output. PSST accomplishes this by clustering the high-frequency horns closely together so there are no gaps in the resulting wavefront, and using a measurement and optimization process to create specific DSP settings for each driver in the array. The low and mid arrays are separated from the high-frequency array ultimately making the system behave like a single giant loudspeaker.
Addressing the issue of directionality from a completely different angle (!) is Groove Tubes. Their SFX technology is intended for musicians who perform through stereo rigs but are frustrated with the typical limitations of doing so: Spreading speakers widely on stage produces a stereo image only for listeners in the center, and listeners to either side miss the opposite channel. SFX overcomes this by employing proprietary DSP and two speakers housed in a single cabinet to create a clear stereo image anywhere in the audience. The technology has been licensed by Fender for their Acoustasonic amplifier and is also available from Groove Tubes for musicians who want SFX Stereo, but wish to keep their existing front-end. Hmmm…maybe they can build us one really BIG stereo P.A. cabinet…
Steve "Woody" La Cerra is the Front of House engineer and tour manager for Blue Öyster Cult. He can be reached via email at woody@fohonline.com.
