Live Sound

Downsizing the Line Array

The list of large-format line array speakers introduced during the past decade is well-known and well-used. But a new generation of compact systems has emerged to provide smaller venues with the bene 7/01/2003 8:00 AM Eastern

The list of large-format line array speakers introduced during the past decade is well-known and well-used. But a new generation of compact systems has emerged to provide smaller venues with the benefits garnered from line arrays. Everyone recognizes the limitations of the big guns: Weight, size, cost and limited ability to bend in a vertical arc have kept line arrays from being much more than a curiosity in smaller venues, where traditional modular speakers are better suited. Smaller, compact line arrays fit smaller budgets and venues better to offer the near-field listening experience to a wider audience.

HOW DO LINE ARRAYS WORK?


There's been much discussion about how sound from an infinite line source defies the inverse square law: Instead of attenuating by 6 dB for each doubling of distance, it only attenuates at 3 dB. This propagation of sound is described as a cylindrical wavefront instead of the usual spherical wavefront generated by traditional speakers and horizontal arrays. As a practical matter, this cylindrical behavior only exists in the near-field of a line array, where a tall column of closely coupled speakers address listeners through a relatively large angle. At farther distances, the array loses its tight vertical-pattern control.

This phenomenon provides improved sound quality in arenas; in smaller rooms, it can guarantee fantastic sound to all seats, provided that the venue's geometry is appropriate. A line array's horizontal coverage is fixed — depending on the manufacturer's design — at somewhere between 90° and 150° wide. If the venue is wider than this, then it must have the side areas addressed by additional side arrays or fill systems. Furthermore, the venue must have hanging points at a sufficient height to get a line array up and properly aimed. Smaller, lighter boxes make this possible in rooms where large-format line arrays would not be practical.

The sound's coherence that is provided by a line array is startlingly clear, as the array elements are vertically arranged so that there is no interference from one enclosure to the next. The coverage throughout the listening area can be very smooth and consistent from one seat to the next, and the difference in sound level can be just a few dB from front to back. This improved sound quality enhances the stereo image so that it can be enjoyed throughout a much larger listening area, not just down the center of the room. A line array can exhibit great pattern control to provide fewer unwanted reflections off of ceilings and walls, plus greater gain-before-feedback for open mics onstage.

WHY A COMPACT SYSTEM?


The limits to using a line array in smaller venues include its weight and height. Smaller, compact enclosures are not only less expensive, but they also weigh less and can more easily bend. Due to coupling issues (for fundamentals on coupling, read “Understanding Coupling” on page 47), there is a limit to how much an angle can be placed in an array from one enclosure to the next. Beyond about 5°, the highest frequencies no longer couple together and instead start to beam, which provides spotty coverage from one elevation to the next.

The advantage that smaller cabinets have is that their arrays can bend for more vertical coverage in a shorter height. In smaller venues, it's not unusual to need 20° of uptilt at the top of the array and even more to get down to the front of the audience: 10 cabinets might need an average splay of 5° just to make this coverage.

The pattern control provided by line arrays extends down to the lower frequencies as a function of the array's height. Arrays lose vertical-pattern control at frequencies whose wavelengths are longer than the array's height. To achieve pattern control down to 100 Hz, for example, an array must be over 11 feet tall and with a typical cabinet height of a foot or less; control down to 100 Hz means using 10 or more cabinets in an array.

Most compact line arrays are not designed as stand-alone systems, but are intended to be supplemented with subwoofers for fullrange response. Most have purpose-designed subs that can be integrated into flown or stacked arrays. And while manufacturers recommend arrays that employ a minimum of four to six cabinets to achieve pattern control down to their lowest octave, there is no rule that says they cannot be employed in short arrays or even by themselves. In fact, some of the smallest models have been successfully used as under-balcony and frontfills due to their height and horizontal dispersion. Other uses for compact line arrays are in short arrays as delay zones in distributed systems for large convention centers, where they can be more effective than individual two-way cabinets with fewer points. Lastly, compact line arrays are the best hope to provide surround sound in live venues due to their enlarged sweet spot.

THE SYSTEMS


Interested in purchasing a compact line array? The following information and specs in the chart below will help you get started; visit manufacturers' Websites for more.

Adamson's (www.adamsonproaudio.com) Y-10 employs a JBL 1.5-inch exit compression driver co-axially mounted with a proprietary 9-inch Kevlar midrange compression driver. On either side of the mid-high chamber is a 10-inch woofer. The company's new (and unnamed at press time) dual 8-inch line array module has proprietary Kevlar Neodymium woofers with a 2.5-inch voice coil and a B&C compression driver.

Apogee (www.apogee-sound.com) was the first manufacturer with a modular line array product, the ALA-3, which employs dual-10s with a pair of conical horns for its two 1-inch compression drivers between them.

EAW's (www.eaw.com) KF730 is a three-way, bi-amped speaker whose entire face is the mouth of a mid-high horn for its dual 7s and dual 1-inch exit compression drivers. Ten-inch woofers are mounted on the two ends of the enclosure. A companion sub, the SB730, employs a pair of high-excursion 12s in a clam-shell arrangement.

Electro-Voice's (www.electrovoice.com) Xlc127+ is a tri-amped, three-way enclosure that uses two of the same compression drivers as its larger X-Line. Its asymmetrical design places a single-12 at one end, a pair of horn-loaded 6.5s at the other and a pair of NDym compression drivers on plane-wave generators down the center. The Xlc124 is the downfill version. The Xlc118 is a companion single-18 subwoofer designed to be flown in adjacent arrays or integrated at a 2:3 ratio.

JBL's (www.jblpro.com) VT4887 is a smaller version of its original large-format VerTec based around dual-12s instead of 15s, and using the same type of pinned hinge bars for rigging. JBL's smallest VerTec, the VT4888, is a bi-amp, three-way, dual-8 enclosure whose quad-4s are passively crossed over to dual- 2407 ring radiators. The VT4881 is its companion single-15 subwoofer. All three of JBL's VerTec Line Array elements can be self-powered by the addition of a Crown-manufactured Drive-Pack.

L'Acoustic's (www.l-acoustics-us.com) dV-Dosc is one-half of the mid- and high-frequency section of its large-format V-Dosc cabinet, the original line array. The triple-15 companion dV-Sub uses the same drivers as the V-Dosc, and is intended for use at a 1:3 ratio to provide identical response in small arrays.

Martin Audio (www.martin-audio.com) is the only company with all horn-loaded line array solutions, and, like its large-format W8L, the W8LC is tri-amped. Its individually horn-loaded elements are able to provide even horizontal coverage down to 500 Hz.

McCauley's (www.linearray.com) M.Line is a two-way speaker that comes in three models with three different high-frequency horns. Nominal vertical coverage of 60°, 90° or 120° allows designers to create systems with high-frequency coverage tailored to a listening area by employing narrower horns at the top and wider horns at the bottom. The company's In.Line is similar to the M.Line, but its simplified rigging system saves weight and cost; it is only meant for permanent installs.

Meyer's (www.meyersound.com) M1D is a self-powered, bi-amped enclosure employing dual-5s and triple dome tweeters. Like all of its dual-woofer speakers, one driver is lowpassed to provide more even midrange coverage. Also available is a companion dual-10 M1D subwoofer. The company's M2D is a self-powered, dual-10 enclosure that employs an amp package similar to the powered UPA and the same compression driver as Meyer's CQ-2. The companion self-powered dual-15 M2D Sub is easily integrated into arrays and packs twice the power of the 650-P. At 235 pounds, Meyer's new dual-12 MILO is a bit too heavy to be called compact, so it fits at the top end of this category. It has a single 1.5-inch compression driver, and above 4 kHz, three 0.75-inch compression drivers take over to provide plenty of highs for long throws. MILO can easily be integrated into M3D and M3D Sub arrays.

Nexo's (www.nexo-sa.com) Geo S805 employs a single 8-inch woofer passively crossed over to a 1-inch driver mounted on its patented Hyperboloid Reflective Wavesource. The S830 is a companion downfill module with 30° of vertical coverage; its companion subwoofer is the CD-12. Nexo's new Geo T4805 employs dual 8-inch drivers, plus another pair of rear-firing 8-inch drivers — lowpassed at 250 Hz — that not only create cardioid coverage in the low frequencies, but also contribute to forward pattern control. Its unusual rigging system, designed by SSE director Chris Beale, comprises the T2815 downfill box that provides 15° of vertical coverage and the companion CD-18 subwoofer.

Renkus-Heinz's (www.renkus-heinz.com) new PNX 102/LA is a two-way enclosure with dual-10s and dual 1-inch exit compression drivers that boasts 150° dispersion with no horn-loading. It can also be ordered as the self-powered PN 102/LA enclosure, which has an R-Control supervision network and weighs an additional 10 pounds.

The SLS (www.slsloudspeakers.com) RLA/2 uses its unique PRD1000 ribbon driver to provide a very smooth high end; coupled with other array elements, it can be used as a planar line source. Though it can run as a bi-amp system, when ordered with NL-8 connectors, the cabinet can be tri-amped and the outside woofer lowpassed at 300 Hz to improve its horizontal coverage in the mids.


Mark Frink is Mix's sound reinforcement editor.

Understanding Coupling


Coupling, the mechanism by which a line array works, is familiar to anyone who has assembled large quantities of speakers into systems. Coupling between transducers occurs when the distance between their acoustic centers is less than half of a wavelength. The best case for 12-inch speakers, with their drivers nearly touching, can provide coupling up to about 550 Hz. For 10-inch speakers, coupling can occur up to 630 Hz, and for 8-inch speakers, coupling can extend up to 800 Hz. (This is why simply putting a hand's width of space between adjacent speakers in a traditional array attenuates the mids.)

At higher frequencies, the drivers' acoustical centers must be even closer for coupling to occur. For coupling clear up to 20 kHz, acoustical centers of adjacent drivers would need to be a fraction of an inch. Clearly, this requirement makes it impossible to create line sources with high-frequency coupling unless there's another way to couple the output of drivers.

Modular line array developer Dr. Christian Heil has shown that the output of individual compression drivers' horn mouths can couple when their output is in phase at all points of the mouth's cross-section and when they are in close enough proximity. The patented DOSC waveguide is his solution for high-frequency coupling from the openings of tall, thin isophasic horn mouths. Different manufacturers have come up with their own waveguides to vertically couple high frequencies from one speaker module to the next, while others have abandoned line array principles at higher frequencies. Readers should understand that it's possible, and sometimes even prudent, to employ a hybrid design that provides low-frequency coupling, while employing multiple horn elements for high-frequency pattern control when an array must be bent more than a few degrees per cabinet. There are line array speakers that, strictly speaking, do not behave as line source arrays at all frequencies.
Mark Frink

COMPACT LINE ARRAYS AT A GLANCE

Manufacturer
Model
$ List
Weight
(lbs.)
Horizontal
Dispersion
(degrees)
Height
Front
(inches)
Vertical
Splay
(degrees)
Angles
(degr.)
Step
Width
(degr.)
Depth
(degr.)
Low-Freq.
Driver(s)
Nom.
Imp.
(ohms)
RMS
Power
(watts)
Crossover
Frequency
(Hz)
Mid-Freq.
Driver(s)
Nom.
Imp.
(ohms)
RMS
Power
(watts)
Crossov.
Freq.
(Hz)
High-Freq.
Driver(s)
Nom.
Imp.
(ohms)
RMS
Power
(watts)
Adamson
Y-10
5,425
150
90
10.5
2.5
0-5
1
42.8
24.5
dual-10
2× 8
700
315
single-9
8
300
2,000
1.5-inch
8
150
Adamson
new dual-8
n/a
62
120
8.5
2.5
0-5
log
26
16.2
dual-8
8
500
300/800
n/a
n/a
n/a
n/a
1.5-inch
8
150
Apogee
ALA-3
3,570
95
60 or 90
14.5
5
0, 5, 10
5
35
13
dual-10
4
600
1,000
n/a
n/a
n/a
n/a
dual 1-inch
4
150
EAW
KF730
5,250
85
110
13
6
1.5, 3, 6,12
log
28.5
17.6
dual-10
16
700
160
dual-7
16
350
passive
dual 1-inch
n/a
n/a
E-V
Xlc127+
4,988
116
120
14.25
3.5
0-7
1
39
22.5
single-12
8
300
500
dual-6.5
8
200

1,600
/passive

1.5-inch
8
150
JBL
VT4887
3,649
62
100
14
5
0-10
1
39
20
dual-8
8
700
300
quad-4
8
225
passive
dual-2407
n/a
n/a
JBL
VT4888
5,699
108
90
11
5
0-10
1
31
16
dual-12
2× 8
700
180
quad-5.5
8
400
1,200
1.5-inch
16
150
L'Acoustic
dV-Dosc
3,600
70
120
10.1
3.75
0-7.5
1
27.4
18.7
dual-8
8
380
800
n/a
n/a
n/a
n/a
1.4-inch
8
66
Martin Audio
W8LC
5,999
128
90
14.5
3.75
0-7.5
1
39.4
21.7
single-12
8
400
300
dual-6.5
8
400
3,000
(3) 1-inch
8
100
McCauley
M.Line
2,995
73
60, 90 or 120
10
5
0-10
1
27.3
18
dual-8.8
8
800
1,200
n/a
n/a
n/a
n/a
1-inch
16
120

January

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