PreSonus StudioLive Loudspeakers and Renkus-Heinz Varia Array System
Consider the term “loudspeaker”—reduced to its two most basic components, it could describe the noisy guy in the pew behind you jabbering away just before the service begins. And that's essentially correct: the story behind the loudspeaker is about being heard intelligibly over distances. That began in 1876 when Alexander Graham Bell patented a loudspeaker as part of his telephone system, and has continued steadily ever since, across milestones in technological developments like the moving-coil design, introduced at the turn of the previous century, that all dynamic loudspeakers are still based on; crossovers that allowed the frequency spectrum to be more efficiently allocated to specialized types of speakers (from high-frequency or HF tweeters to low-frequency or LF subwoofers); to the introduction of line array designs based on acoustical pioneer Harry Olson's designs in the 1950s and the introduction of the first viable commercial touring system, L-Acoustics' V-DOSC system 40 years later. The spaces between the high points on the loudspeaker timeline are many and varied, and those tweaks continue to refine this most basic element of any sound system.
“The developmental history of loudspeakers in general over the last decade or so is really about incremental improvement rather than anything truly revolutionary,” observes Gerry Tschetter, vice president of marketing at QSC Audio with U.S. offices in Costa Mesa, Calif. “I'm not sure that if Jim Lansing were to come back today he'd be all that shocked at what's happened.” (James B. Lansing, audio engineer and speaker designer whose initials form the name of one of the most iconic speaker manufacturing companies, died in 1949.) But, says Tschetter, even the incremental enhancements, such as better power capacity and power handling as a result of improved materials and manufacturing techniques, are significant when their collective effects are considered. Here are several key paths of development in relatively recent loudspeaker technology and how they impact the house-of-worship market.
POWER (OR NOT) TO THE PEOPLE
The dichotomy between powered (aka active or self-amplified) speakers and so-called passive speakers (indicating remotely powered and a term that was compelled when powered speakers came along, just as we needed “analog” after digital appeared) remains in place decades after self-powered PA speakers came on the scene. What was once the domain of a handful of manufacturers is now a well-developed category, and many of the leading brands offer both types of speakers in their product lines.
Broadly put, active speakers have their amplification sources integrated into or very proximal to the loudspeaker enclosure. Passive speakers use amplifiers that can be positioned in locations other than where the speakers themselves are; they can also share banks of amplifiers, meaning there can be more speakers than there are amps. The advantages of the former include assured proper matching of parameters, such as power and impedance, between speaker and amplifier that prevents overloads that can negatively affect sound quality; simplified installation and operation, with speaker and amp in the same location; inherent redundancy: the loss of one amplifier is just that—it will not take part or all of the rest of the system out with it. However, powered speakers cost more on average than passive ones, although this cost differential has been steadily declining in recent years. Other issues include more weight for flown systems, affecting installation and hang-point strength, and the need to have AC power and audio signal available at every hang point, sometimes requiring additional conduit to be installed.
Passively powered speakers, on the other hand, have their own set of benefits. These include lower average costs, which make them easier and cheaper to repair or replace and easier to upgrade than an active system; passive speakers only require a single input and can be wired either serially or in parallel; passive speakers are, generally, much lighter than active ones, making them more portable or easier to install. On the other hand, grouping amplifiers into banks needed for a passive system requires additional cooling capability, and the cable runs between amp and speaker have distance limitations that can contribute to an overall loss of peak power in the system.
The utility of passive speakers might be said to have been somewhat eclipsed by how active speaker systems have attracted more technological innovation in recent years, particularly when it comes to weight/power ratios, which have been progressively reduced over time. But passive systems have been getting more of their cutting-edge due lately. For example, Crown Audio's VRack that utilizes the company's I-Tech HD amplifiers with DSP coupled with the JBL VTX passive loudspeaker systems creates a hybrid, with power and processing able to be integrated into a scalable system with multiple speakers using a single VRack.
“The VTX line is all outboard amplifiers for now,” says Jon Sager, senior manager of installed sound for JBL in Northridge, Calif. “It's one of a number of tools that houses of worship can choose between for their sound systems.” Sager points out that self-powered loudspeakers dissipate their heat energy into the audience space, so there is no need to budget for the physical plant space and cooling infrastructure of an amplifier rack room. Also, he adds, “Taking the calibration of gain and crossover settings out of the equation, self-powered systems eliminate the guesswork of matching elements coming from different manufacturers who use different methods to measure their products and report the results; self-powered loudspeakers have the complex settings and wiring already done and dialed in. This makes setup and operation quick and easy for system techs and operators at all levels of experience.”
Speakers may not have changed that much over the last century, but even their incremental evolutionary developments have considerable positive impact for getting a message across clearly.
THE NETWORK
Networked sound is the major buzz phrase today, and it underscores the fact that audio in general is—like video—converging onto a shared environment with IT/IP functionality. There are two distinct areas of networking when it comes to audio: the audio itself moving to an IP domain, in which it is packetized and moved over Cat-5/6 and fiber cabling (vs. conventional copper wiring) along with other data, and the control of audio systems moving to a networked environment.
Networked Audio: In a relatively brief period of time, a number of networked audio solutions have come to market, including systems from Audinate (Dante) and Riedel (RockNet), which join established networking solutions CobraNet and EtherSound. They all have in common the mission to transport digital audio in an uncompressed format with sufficient bandwidth, a high sensitivity to latency (delay), and in packets that are fully synchronized yet completely separate and isolated from any other data on the network.
The leading edge of networked audio is audio over Ethernet (AoE), replacing snakes made from many strands of bundled copper wiring with Cat-5-type structured cabling. Audio over Ethernet requires a high-performance network such as a dedicated local area network (LAN) or virtual LAN. There are several different protocols for audio over Ethernet, and they vary according to their speed and resolution of the audio. For instance, using Cat-5 cabling and 100Base-T signaling at 100 Mbits/second, each audio link can generally transmit between 32 and 64 channels at a 48 kHz. Other systems can handle other rates, such as 44.1 kHz, 88.2 kHz and 96 kHz, in some cases attaining even 192 kHz, as well as up to 32-bit sampling rate. However, increases in speed and resolution generally come with corresponding decreases in channel capacity.
Networked Speakers (and Amplifiers/DSP): Apart from the audio itself riding on a network, the networked control of digital audio is another growth area for loudspeakers as well as amplifiers and DSP systems—think everything but the audio itself riding on a LAN. Systems such as Harman's HiQNet, QSC's Q-Sys and Renkus-Heinz's RHAON are communications protocols—languages that can speak to components on an internal network. These tend to be proprietary networks—HiQNet is solely available for components from companies within the Harman Pro Group—JBL speakers, BSS Audio DSP systems, Crown amps, etc.—and are managed by specific software, in this case, Harman's HiQNet System Architect.
“In either type of network, audio-over-IP or control of the audio such as via HiQNet System Architect, what you're gaining is a streamlining of the process,” says Sager. “Audio is fully digital from the stage to the FOH mixing console and to amplifier racks or directly to the powered loudspeaker systems, all of the components are completely able to be monitored from a central location, and all of the parameters for the components—delays, EQ, crossovers and so on—are also centrally managed and controlled.”
Tschetter reports that the benefits of networked audio for houses of worship are the same as for any other facility. “Audio networking allows a large number of audio channels to be routed to and from disparate locations,” he explains. “Depending on how many channels there are and how many origin points and destinations, sending audio via network can be considerably less expensive than running analog audio around a facility on shielded-pair wiring.”
He adds, “A networked audio DSP system can also manage signal routing, thus eliminating the need for expensive and complicated patch-bays. The same DSP system will also likely be capable of replacing racks of signal processing—equalizers, dynamics and signal delays.” (Via its Q-LAN element, Q-Sys can network both control and audio-over-IP.)
Tschetter adds that if the house of worship already has an IT infrastructure installed, it's even possible that it can be used for audio distribution. “However, whether networked audio makes sense for a particular venue really depends on a huge number of factors,” he cautions. “A simple system with just a few sends and returns from stage to mix position and back plus a cry-room feed probably would be wasting money on a networked system; at the other extreme, a ministry with multiple facilities on a campus may find it difficult to accomplish their desired audio distribution any other way.”
STEERING COMMITTEES
Active digitally steered speaker arrays are another relatively recent development that's become a major trend in loudspeaker system design. The passive steerable speaker array has been around even longer than the line array, but the addition of digital signal processing and other types of software control that can alter the projection characteristics of the speaker array—whether in a hanging line array or a columnar array—is a game changer.
An array of smaller speakers, all driven in phase, is the equivalent of several larger speakers, but with additional inherent directivity. Coupled with DSP that can enhance this natural effect, steerable arrays are of particular use to houses of worship because of their high directionality in the one-kHz range, the sweet spot for speech intelligibility. The “beam” of sound produced by these highly directional arrays can be focused on specific areas of a space. This is especially useful in keeping sound away from reflective surfaces such as hard walls and floors, where reverberation can smear the original source sound.
Steerability control will decrease as you move down the frequency spectrum, so a key criterion for choosing steerable arrays is the lowest frequency possible for a given system where the speaker can still maintain pattern control. But an increasingly common strategy in steerable-array sound is the cardioid subwoofer. These can take two forms: a single product, such as the Meyer Sound PSW-6 or the d&b B4-SUB, and multiple subwoofers configured in a cardioid array. In both cases, they come down to three elements, one of which is facing 180 degrees away from the other two, creating a phase inversion that cancels out reflected energy. To cap this basic configuration off, according to Bennett Prescott's excellent analysis of cardioid subwoofer physics on SoundForums.net, “Delay is then applied to the rear-facing subwoofer to time align all loudspeakers toward the rear. Inverting the polarity of the rear-facing subwoofer then creates cancellation as the energy from the front-facing subwoofers arrives only to be met by the inverse energy radiated by the rear-facing subwoofer, which nullifies it.”
“Cardioid subs are an effective way of extending steerability well into the low-frequency ranges,” says Sager. “They're particularly useful for churches where low-frequency build-up can create intelligibility problems.”
In closing, speakers may not have changed that much over the last century or so, but even their incremental evolutionary developments have considerable positive impact for getting a message across clearly.
