Technology

Line Arrays

FOR THE PAST TWO DECADES, most large-scale sound systems have been configured as multicabinet typically made up of components either purchased from a 3/01/2001 7:00 AM Eastern

FOR THE PAST TWO DECADES, most large-scale sound systems have been configured as multicabinet “clusters,” typically made up of components either purchased from a handful of manufacturers or designed and built by sound equipment rental companies. But the ’90s saw the arrival of a new style of cluster, the line array, and, as the decade progressed, several major U.S. sound companies fielded systems based on this “new” technology. But whereas many system designers and engineers are familiar with the theory and practice of implementing multicabinet, multidimensional arrays, relatively few have had much experience installing and operating line arrays. To find out more about the practical aspects of using line arrays, Mix interviewed a select group of sound system designers and users. Our thanks to Lars Brogaard, Robert “Cubby” Colby, Scott Harmala, John Meyer and Robert Scovill.

In its most basic form, a line array is made up of identical loudspeaker components arranged in a vertical line. Line arrays have two striking characteristics: Doubling the number of drivers in the array results in a 6dB increase in SPL in the far field at all frequencies; and the vertical coverage angle of the array is largely determined by the number of drivers — the more drivers in line, the narrower the vertical coverage angle. (The horizontal coverage angle remains largely unaffected by the number of drivers and is typically about 80°, depending on the components used.) Because of the “6dB doubling effect,” a single line array can outperform a conventional multisource cluster in long-throw applications, and almost every major sound system manufacturer is either planning a line array system or has one in production — at least three line array systems came to market during 2000. (See the October 2000 edition of Mix for Technology Spotlights on Electro-Voice's X-Line and JBL's VERTEC line array systems.)

“It's the way of the world right now,” says independent engineer Lars Brogaard, who recently used a new Electro-Voice X-Line system for the Diana Ross & The Supremes tour. “This is what everybody is going to have to do now because it just makes sense. It's easy to work with once you know what you're doing, and it takes up less space.” Equally important, adds Brogaard, “For me, it just sounds a lot better. It's much more controllable.”

THE SHAPE OF THE CLUSTER IS KEY — IT HAS EVERYTHING TO DO WITH THE PERFORMANCE OF LINE ARRAY. IT ISN'T A MATTER OF JUST PUT UP 10 BOXES AND PUT A CURVE ON IT.
— SCOTT HARMALA

Line arrays are not new — the principles were first described in the 19th century — and, before sound companies started building their own horn-loaded and direct radiating systems in the late ’60s, most bands were amplified through line array P.A.s, or “columns.” Shure, University and UK-based WEM are names that rise from the fog of memory, but many other manufacturers made line array-based systems for public address and live music applications. However, line arrays have certain inherent limitations, and, faced with the demand for high SPLs, wide coverage and portability, live sound system designers increasingly turned their attention to modular horn-loaded systems. Apart from the notoriously impractical “Wall of Sound” system developed for the Grateful Dead in the mid-’70s, line arrays were largely absent from the U.S. touring scene until the early ’90s. That was when AudioTek, a Burbank, Calif.-based sound company that specializes in sound for TV awards shows and special events, first became interested in a new line array system designed by Dr. Christian Heil and manufactured in France by L-Acoustic.

Scott Harmala, AudioTek's chief engineer, takes up the story. “We are probably the first users of V-DOSC in the United States — we've been using it for, gosh, probably at least nine years. Jeffrey Cox, who was originally the sound guy at the Universal Amphitheater here in town, got word of this new system in France, and he went to check it out and was incredibly impressed by the technology and by Dr. Heil and just the whole package.” Cox was in fact so impressed that Cox Audio became the North American distributor for L-Acoustic and the V-DOSC system. AudioTek, which already had a long-standing relationship with Cox, was among the first users of the 16-box V-DOSC system that was sent to the U.S. as a demo.

“At that time, we realized that line arrays had incredible potential, especially in this specialized [TV awards show audio] business we were in back then,” continues Harmala. “Dealing with lavalier mics and podiums and other difficult things onstage in fairly large venues, the directional characteristics of the line array really gave us a lot of gain before feedback, a lot more than any conventional system that we'd experienced before.”

Independent engineer (and six-time TEC Award winner) Robert Scovill was also favorably impressed. “The first time I ever ran into the V-DOSC system was at an awards show,” he recalls. “It had just come over, and Jeff Cox, who was the house sound guy at the Universal Amphitheater, where they were holding the event, was kind of extolling the virtues of it, etc., etc. And at the time — especially in that setting — I was like, ‘Yeah, okay, whatever. [Laughs.] I'm not sure I'm buying it.’ But having said that, upon listening to it throughout the day — because I was just a guest mixer, I was walking around listening to the other talent on it — I was thinking, ‘Man, this is really good in terms of its coverage.’ I had heard a lot of shows in the Universal Amphitheater, and that is not an easy room to cover. Just in terms of hanging P.A. and getting one that will cover that room properly has always been a big challenge. At any rate, I remember walking around and thinking, ‘Man, the vertical coverage here is really, really good.’ As well as the horizontal, for that matter. It was as good as I had heard it there.”

It was not just the coverage characteristics of the V-DOSC system that drew positive reviews. “It would be very difficult for me to go back to any of the conventional systems that have been around, even though they were all very good, and they all still are very good,” says independent engineer (and perennial TEC Award nominee) Rob “Cubby” Colby. “Primarily, it's been this incredible difference in vocal intelligibility and overall dynamics. For really percussive music, like, say, Latin music, which is currently what I'm doing with Ricky Martin, [the V-DOSC system] can really deliver the dynamics of the music really clearly and for a very long distance. So no matter where I've been mixing in these bigger arenas, it's always been a pleasure to listen to the P.A.” In addition to the V-DOSC system, Colby has also mixed on the Clair Bros. I-4 and JBL VERTEC systems and is unstinting in his praise for all three. “The line arrays that I've used have been extremely accurate and very musical,” he adds. “When you reach and turn your EQ knob, they're really responsive in a positive way.”

“On V-DOSC, much like in a studio setting where you have control room monitors, if you're a bad mixer, it's going to show you as a bad mixer,” notes Scovill. “If you're a great mixer, it's going to show you as a great mixer. There won't be this averaging down of the P.A. system where, if you're on a system that's terribly comb-filtered and really doesn't sound that good to begin with, if you're a great mixer, it's going to average your mix down. Whereas if you're a bad mixer, it's going to average your mix up.”

WHY NOW?

Articulation and dynamics, predictable coverage and a space-saving truck pack are among the P.A. system characteristics most highly valued by FOH mixers and sound rental companies. But why, if line arrays are now so widely praised, were they widely ignored for two decades during the major growth period of the live sound industry?

“What's really elegant about a line array, a pure line array, is that every time you double the number of elements, you get exactly a 6dB increase in frequency response at all frequencies,” says John Meyer, founder of Meyer Sound Labs. “This is all when you're far, far away — hundreds and hundreds of feet away, or thousands of feet away. When you're in the near-field, you have a whole other set of cancellation problems that occur, which was why people didn't like line arrays and why they disappeared. All the column-type speakers disappeared because when you were in the near-field of the things, 10, 20 feet away, and you stood up and sat down, you heard great interference patterns. So they kind of fell out of favor.”

As large-scale sound systems became more common, system designers occasionally revisited line array theory, but back when P.A.s were typically stacked on stages or risers, the narrow vertical coverage angle sometimes worked against them. “We worked on line arrays with the Grateful Dead, I don't know, 30 years ago, or whatever it was — I guess it was around 1970 they were doing their ‘Wall of Sound,’” says Meyer. “We found, when we were doing line arrays at Winterland, that there was no bass in the balcony.”

The “Wall of Sound” consisted of many individual towers of instrument and vocal speakers, essentially a system of multiple line arrays. Though each speaker tower was of a different length, none were so tall that their acoustical centers aligned with the balcony, so the bass frequencies would typically be projected along the plane of the auditorium floor and under the balcony.

Whatever problems current line array users have with the low end — several current touring line array systems include flown or stacked subwoofers — the narrow vertical coverage angle of line arrays can be used to an advantage in certain situations. A properly positioned line array can be aimed to cover only the audience area on the floor, thereby minimizing the reverberation and slap echo that inevitably result when a P.A. system's coverage area includes building surfaces not covered by the (highly absorptive) audience. For most large-scale reinforcement applications, a line array must be hung from the auditorium ceiling or purpose-built support towers, which makes aiming the system particularly critical.

RIGGING MATTERS

“I started having to learn alternate rigging techniques for V-DOSC,” says Harmala. “We were very excited about reaching a new envelope that we'd only dreamed about being able to hit before. But we were struggling with it in terms of application, because in order to have it be an effective system, you do need a fair amount of boxes in-line. Anywhere from six to eight, typically. And a lot of times, especially in TV, it's a very difficult thing to try to sell, because it's a long, vertical strip of stuff. And in TV, the whole idea is visuals. Audio is low man on the totem pole, unfortunately, until there's an issue. But, as a general statement, we're put in the backseat. [The V-DOSC system] has to be rigged and positioned to be effective, yet it has to be out of sight. So it was very difficult for us in our early days to figure out how to do it. Where to put it, in order to make it work and have it visually out of the way.”

One of the factors in favor of line arrays is the relative compactness of the system and the minimal rigging requirements, especially compared with the number of hanging points necessary for the typical flying P.A. system. “The VERTEC system is extremely versatile in terms of rigging,” says Harmala. “With a combination of the rigging design integral in it, and with two different types of rigging frames, you can rig it in any orientation. In other words, you could build the thing to be spraying straight down, laying as a flat line array spraying straight down if you wanted to.”

As Harmala explains, there are also situations in which a line array, or at least part of it, must be aimed upward. “We've done jobs here at the Los Angeles Coliseum, one of those old stadiums that is one continuous rising bleacher section all the way up from the field all the way to the back, so it's really deep and tall. So if you're doing a gig there with maybe 50-foot scaffolding and you can rig your clusters 40 feet high, you're shooting like 15 or 20 degrees up in the air in order to hit the guys way at the top.”

SOME ASSEMBLY REQUIRED

The key to successful implementation of line arrays is a clear understanding of their capabilities. “Line arrays are very elegant, because they allow you to put more power into one area,” notes Meyer. “As you keep adding units in the line array, you keep increasing your power. Every time you double the number of drivers, you double the power at the same position in the far field without interference. And this is much better than trying to crossfire a lot of speakers into that area. So when you're trying to get a lot of power at a long distance, line arrays are very good.”

However, in all but a few situations, that segment of the audience nearest the stage will not be sitting (or standing) in the far field coverage pattern. For that reason, most of the line array systems currently in use are hung in a gentle arc or in a “J” curve with the lower part of the curve designated as a downfill or near-field system. Depending on the system and its configuration, this curve can introduce more problems than it solves.

“We started experimenting with arcs with the Grateful Dead, because we were trying to figure out how to get sound in the balcony,” recalls Meyer. “But when you get into arcs, you start getting into real problems with directionality — certain frequencies become more directional than others. Line arrays are true line arrays only when they're straight; once you curve them, they're no longer line arrays — an arc is a different thing. As soon as you curve the array, you get some frequencies that spread and some frequencies actually get more directional, depending on the curve and the radius of the curve.”

PAGING DR. HEIL

“You really need to understand the physics and the science in order to really apply it and maximize it in the right way,” says Harmala. “I've seen a lot of V-DOSC [systems] used in the wrong way on a whole bunch of different shows, and a lot of it is because they just don't understand, and they're thinking of it in terms of conventional cluster layouts or designs. You gotta kind of drop all that you've been operating on for years and years, and you gotta kind of re-learn a new way of thinking about how to do this. And the fact that you can actually contour the SPL across the cluster is a very powerful thing that's very underrated. One of the things that Heil doesn't prescribe that we regularly do is that we split-process our clusters. We will divide clusters into a long-throw environment and a near-field environment and apply different processing to those different areas. In terms of purist line array mentality, I guess you could say that is a no-no, but in terms of application in real-world performance, we found it to be a must.”

As Harmala implies, owners and users of the V-DOSC system are expected to hew to the manufacturer's recommendations on array angles, power configuration and processing, and those recommendations are proprietary. Before Robert Scovill embarked on his first tour with the system, he took the initiative to attend the V-DOSC training. “I was all for [setting up the system] via the method that they prescribed,” Scovill recalls. “I'm kind of one of these guys that says, ‘These guys have done all the research and spent all the man-hours on it. How about we give it a shot at how they're doing it before we come in and start changing things?’ Sure enough, over time, I don't think I've changed anything on the P.A. I've used their guidelines for coverage and just been thrilled with it.”

Lars Brogaard takes a more empirical approach. “When we did the [Diana Ross tour] with the Electro-Voice X-Line, we played around a lot with the crossover points, to where it would sound the best between the components,” he explains. “We [also] did that a lot with the V-DOSC system when I used that. They have certain factory settings, and they might be fine for one venue, but those factory settings are not great for another venue. If you don't have enough cabinets, you don't get the [low-end] coupling out of it, so [you have to modify] your crossover points — how low you go with your 15s before you bring the sub bass in. I would vary that a whole lot — from down to 40 cycles up to 80 cycles, that crossover point there — and move it around until you get where it sounds the most in harmony.”

Harmala is more analytical, if no less skeptical. “We started really doing some very heavy, heavy analysis and measuring of V-DOSC,” he says. “And I realized the only way I'm going to really find out the facts is to analyze it and find it out myself. Our company has developed a lot of speaker systems, proprietary stuff, so we're pretty up to speed in terms of dealing with measurement techniques. So I started a campaign of looking at what you can actually do in terms of wrap angles, the effects of different cluster shapes on performance and things like that. I started to learn a lot — some stuff that's true and some stuff that's false in terms of understanding how line arrays work. The shape of the cluster is key — it has everything to do with the performance of line array. It isn't a matter of just put up 10 boxes and put a curve on it. The shape of the curve dictates the performance in the far field and near-field dramatically.”

Of course, the arced section of a “J” curve line array is typically designed to cover that segment of the audience closest to the stage, an area that few, if any, FOH engineers choose to mix in. And though most sound engineers profess themselves interested in achieving even coverage throughout the room, those engineers who consistently praise line arrays include many who obviously enjoy the mixing aspect of live sound work and whose professional reputation depends on that ability — as heard at the FOH position. To those mixers who spend the entire show in the FOH compound, relying on their system techs to walk the house, it seems sensible to point out that getting a great sound at the mix position does little good if a large section of the audience is hearing something very different.

For a variety of reasons, not every live sound company will join the rush to invest in line arrays, but there is no doubt that they are here to stay. The systems deliver on at least some of the claims of their designers and promoters, a significant number of “golden ears” FOH engineers endorse one or more of the competing systems, and production managers, once they adjust to the different silhouette, are generally impressed by the ease and speed of rigging. However, there are some situations in which conventional arrays may be more appropriate.

“You don't have any control over the horizontal [coverage pattern],” notes Meyer. “So if you have a line array that's 90 degrees, it has to fit the space that you're putting it in. If it doesn't fit very well… We could never use line arrays in Carnegie Hall, it's too long and narrow. You need to be able to shape the array, so it's never going to be practical for something like that.”

YOU GOTTA KIND OF DROP ALL THAT YOU'VE BEEN OPERATING ON FOR YEARS AND YEARS, AND YOU GOTTA KIND OF RE-LEARN A NEW WAY OF THINKING ABOUT HOW TO DO [LINE ARRAYS].
— SCOTT HARMALA

And though the frequency response anomalies caused by curving a line array may be correctable via DSP, a processor-based solution may prove expensive, or at least no cheaper than existing tools and techniques. “There's a certain level of marketing that's going on with line arrays that's not really good science for the professional trade,” notes Meyer. “The manufacturers are not really showing why they came and went last time. Like any tool, there's limitations.”

Chris Michie is a Mix technical editor.

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