RE/P Files: Electrotec’s System For Roxy Music, August 1983
New Lab-Q loudspeakers in operation at San Diego State University three decades ago...

March 23, 2014, by David Scheirman

re/p files

This article, from the archives of the late, great Recording Engineer/Producer (RE/P) magazine, provides an in-depth look at a new concert sound loudspeaker system unveiled in 1983 by leading touring company Electrotec. The text is presented unaltered, along with the original graphics.

Roxy Music has not toured in the U.S. since the late Seventies. The band actually dissolved in 1979, and only came together again during early 1982 to produce Avalon; in April of this year, the group was on the road to promote that album, as well as the recently released, live four-song “mini LP,” The High Road.

Twenty-six shows were scheduled over a period of 30 days, in various venues around the country ranging in size from 6,000- to I6,000-seat capacity. According to Roxy Music’s production manager, Chris Adamson, those 26 shows were very important to the group as it attempted to re-acquaint concert-going audiences with its music.

Electrotec Productions, Inc. (formerly TFA) was selected to handle sound reinforcement for the tour, as well as supply stage lighting. Of particular interest was the fact that Electrotec’s sound system for Roxy Music included the recently completed Lab-Q series loudspeaker cabinets,

Regarding the group’s choice of sound companies, Adamson says, “It was basically a mutual decision made at management level. Robin Fox, our house engineer, felt that the new Electrotec system would be a good vehicle with which to present the group’s new material, and we were particularly interested in finding a company which could offer a package deal on sound and lighting.”

House engineer Robin Fox (left) and monitor engineer Bill Chrysler.

As Robin Fox recalls, “At rehearsals, I used four pairs of the new speakers in the main room at Studio Instrument Rentals [Hollywood], and I was favorably impressed with them indoors. This tour has a lot of indoor dates, but the outdoor shows are where we will really tell whether or not a system has what it takes. So far, I think we made a good choice.”

Lab-Q Loudspeaker System
The Electrotec Lab-Q is a three-way active/fourth-way passive, two-cabinet speaker system, capable of being stacked on the ground, or flown in the air with no additional special hardware. According to Pierre D’Astugues, Electrotec’s senior vice president, the new system is the result of more than three years of research and development.

“The low-end of the system was computer-designed and manually tuned so as to offer a response to below 40 Hz,” he says. “Our mid-cabinet is also computer-designed, and can achieve a true 60-degree coverage angle. Right now, the system is at a certain point in its evolution; this is not necessarily where we plan to stop with it. The basic cabinet structuring will be a constant, but as new transducer and electronics technologies hit the market we plan to adapt this system to fit the new developments.”

D’Astugues feels that the Lab-Q system is fully taking advantage of today’s available technology, but that a 10% to 15% improvement in the system will be evident by next year, due to engineering advances. “Feedback from engineers—[both] our own, and those employed by the accounts we service—is bringing about positive changes, and this system is exciting in that respect,” he remarks. “It is an ongoing thing. Crossover circuitry, transducer manufacturing technologies, and component alignment are all three areas where advances will occur.”

Figure 1 (click to enlarge)

System Low-End
The Lab-Q low-end cabinet, of which 26 were used on the Roxy Music tour, houses a single 18-inch cone driver capable of handling 600 watts RMS. “The speaker is not currently available to the public,” explains D’Astugues. “It has been developed especially for us by JBL, and is a bit different from the similar, commercially available speaker.” When pressed for details, all he would offer by way of elaborating was that, “it’s more
expensive, I’ll tell you that much!”

The cabinet, which covers the sound spectrum up to 250 Hz, is a folded-horn design with center bracing, and currently is equipped with two round porthole vents (Figure 1).

System Mids and Highs
The second half of the loudspeaker system is a cabinet of identical dimensions designed to stack directly via locking corner mechanisms on top of the low-end cabinet, and thus create columns that tower approximately 8 feet above ground level. The mid/high cabinet contains two 12-inch JBL E120s loaded in a deep horn chamber; a new constant-directivity, bi-radial horn mounted on a JBL 2445 driver; and two specially modified JBL ultra-high frequency units that are passively crossed over (Figure 2). The system crossover point between the 12-inch speakers and the compression driver is 1.5 kHz.

Figure 2 (click to enlarge)

The combined mid/high cabinet is rated at 400 watts RMS in the mid-range section, and 200 watts RMS on the top end. Coverage pattern of the horn-loaded 12-inch speaker section is matched to that of the bi-radial fiberglass horn, giving the cabinet an even 60 degrees of horizontal dispersion, Electrotec claims.

The cabinets arc constructed of a very dense plywood, manufactured with a patented process. “The wood is of considerable importance when putting together a speaker cabinet,” says D’Astugues. “Many people tend to ignore that part of the design process, but we have gone to great lengths to find the best material. The sound damping of the Lab-Q boxes is so good that nearly all of the energy goes into projecting the audio to the front of the cabinet, where it should be; walk around behind the box, out of the coverage pattern, and you will find very little SPL back there.”

According to D’Astugues, there has been no “magic” involved in the development of the Lab-Q system, just correct application of currently available speaker system technologies, a lot of trial and error, and much hard work.

System Electronics
At time of writing, Electrotec has been using Soundcraft consoles several years now, and its custom-designed version for slightly more than a year. The consoles have a distinctive custom metalwork outer housing finished in chrome (Figure 3). The module configurations are unique to the Electrotec boards; Soundcraft is building this console series especially for the PA company.

Figure 3 (click to enlarge)

According to Soundcraft’s technical manager, Shane Morris, “These desks are similar to our Series Three in some ways, but they do not have any dual-concentric knobs ... every function is laid out with a separate control. The desks are equipped with a front-access patch panel which utilizes Switchcraft mini-patch cables, and which is protected by a clear plastic cover on hinges.”

House and monitor consoles are nearly identical in appearance. The monitor console is equipped with 32 inputs, 16 outputs, and two additional effects sends; it offers four-way parametric EQ on all input channels and 16 outputs. The front-of-house console is equipped with 40 input channels, eight subgroups, and six effects sends.

The Electrotec Soundcraft consoles have been designed to operate on 120 volts AC. Since most regions of this country have a slight variance in their available AC voltage, a Variac is put in the line which feeds the 12-volt DC power supply, to step up the voltage to ensure a consistent 120-volt source.

At the Roxy Music concert in San Diego attended by this writer, the available AC supply measured a slightly unsteady 118V—just low enough to possibly cause the consoles to lose headroom, and become unstable. To prevent problems, the Variac boosted the AC voltage to 123 volts; the unit also includes an AC power line monitoring meter, which is always handy to have around.

House Signal Processing
As supplied for Roxy Music’s house mix engineer Robin Fox, the Electrotec system was equipped with the company’s standard Brooke-Siren Systems Model 340 electronic crossover (Figure 4).

This device has a built-in limiting circuit on each pass band that is individually tuned for the affected frequency range. Input subsonic and high-frequency filters are offered with 24 dB per octave filter slopes. Crossover cards are of modular design.

Figure 4 (click to enlarge)

House equalization was accomplished through the use of White Model 4000 third-octave filter sets, which feature rotary-pot controls as opposed to a graphic layout. A White real-time analyzer provided Fox with an accurate display of the system’s frequency response and sound pressure level. An AKG C451E microphone supplied signal input to the analyzer, while an internal pink-noise source is available for system testing.

Other signal processing equipment in the house system included dbx Model 160 limiters for the main left and right outputs, and another pair of the same device for patching into the kick drum and bass guitar channels. Four Audio + Design Scamp Model 100 noise-gates were patched into drum input channels, and four Scamp SOl compressors were available for processing vocals.

Figure 5 (click to enlarge)

Special effects devices included a Lexicon Model 224 digital reverb, Marshall Time Modulator, Audio + Design Compex F760XRS stereo limiter, Eventide H949 Harmonizer, and an AMS Model DMX 1580S stereo digital delay. House processing gear was contained in three identically sized 19-inch rack-mount cases (Figure 5), and was tied into the house mix console via dedicated multipair cabling.

In the house system, playback of prerecorded music was accomplished with two ReVox two-track reel-to-reel decks and an Akai stereo cassette player.

Power Amplifiers
Electrotec has chosen the JBL Model 6233 as its exclusive power amplifier for both house and monitor systems. The Model 6233, because of its high-frequency switching power supply, weighs only 34 pounds per unit, yet develops 400 watts RMS per channel into a 4-ohm load.

Figure 6 (click to enlarge)

A total of 63 of these amplifiers were on the road with Roxy Music, packed three to a case: 18 for the monitor system, and 45 in the house.

Each amplifier rack has front-panel access to inputs and outputs, and AC connectors for each rack located at the base of the front panel (Figure 6). The 6233 amplifier contains one possibly unique design feature: a front-panel foam-lined vent provides flow-through ventilation to cover cooling requirements, so that units may be stacked directly one on top of another to conserve rack space with no ill effects.

System Set-Up
The concert that this writer observed was staged at San Diego State University’s outdoor amphitheater, an open-air stage below ground level with high-rise concrete seating that describes an area of nearly 140 degrees.

To adequately cover such a venue, the main speaker stacks must be laid out to provide unusually wide coverage.

Electrotec sound system engineer Mike Gibney chose to set up the system in two stacks of 21 boxes each. The stacks were given a slight hemispherical curve out to the sides, and in towards the center of house (Figure 7). Low-end cabinets were arranged in columns of three, and mid/high cabinets put up in similar fashion.

The center of each stack comprised two columns of three low·end boxes apiece—quite a concentration of low-frequency energy in one spot. Since the distance between stacks was in excess of 60 feet, the monitor sidefill stacks were called upon to do double duty as center-house fill. Sidefills were placed slightly upstage of the front mike line, and angled across the downstage performing area, with their coverage pattern
hitting the center house seating sections.

Figure 7 (click to enlarge)

The San Diego concert was only the second show of the Roxy Music tour. Since the system was fresh out on the road from rehearsals, much time was spent during the afternoon before sound check carrying out basic road preparation: cables were labeled, case packing charts prepared, and loose hardware tightened.

According to Gibney, basic system maintenance never ends when a system is on tour. “Every day there are things to watch for, gear to check on,” he says. “For instance, right now I am tracking down a hum in the house system, which is not normally present with this gear. There seems to be a ground loop occurring at the interface between the house and monitor consoles (splitter box), and it is a trial-and-error process to isolate and correct the problem.”

As Gibney got the main stacks in the air and hunted down the few inevitable bugs, Electrotec engineer Chris Amison tuned the system for the band’s engineer, and then proceeded to start the stage input hookup.

Stage Miking
Roxy Music features vocalist Bryan Ferry and saxophonist Andy Mackay, both of whom worked the downstage area. Ferry’s vocal mike was a Shure SM-78, while the sax was picked up with two inputs: an AKG D224E was fed into a small Yamaha self-contained 6-channel mixer, sweetened with a Roland Space Echo, and fed through Yamaha speaker cabinets, one of which was miked. Additionally, a wireless unit was taken as a direct input for a clean, unprocessed signal.

Electric guitar amps were miked with Shure SM-57s, while the bass guitar was taken as a direct input, as were the keyboards. A Yamaha 12-channel mixer received signal input from Guy Fletcher’s two Roland Jupiter synthesizers, Solina string synthesizer, Korg organ, Yamaha CP-80 electric piano, and Wurlitzer electric piano.

The resultant mix was processed through a Roland SDE-2000 delay unit, and then sent to the house and monitor consoles. Additionally, a direct input was taken on each individual keyboard instrument to ensure clean signals at the desks.

Figure 8 (click to enlarge)

Roxy Music’s stage set this time out contained a generous amount of percussion, as can be seen in Figure 8. Andy Newmark’s large drum set, complete with gong, was picked up with two overhead AKG C414EB condenser mikes. Toms were miked individually with Sennheiser MD421s. and the kick received an Electro-Voice RE-20. The snare was miked from the top with a Shure SM-57, and hi-hat cymbals given an AKG C451 E. The auxiliary percussionists’ congas, roto-tom, chimes, and bells were picked up with a pair of Beyer M160 mikes.

A three-way splitter with individual ground-lift switching on each input line passed the signal to the house and monitor consoles, leaving one split available for broadcast pick up or recording. Model 8226 AMP brand connectors on 11-pair multicable carried the microphone signals to the splitter box from satellite plug·in boxes distributed around the performing area. These boxes were designed with an extra female connector on the end, so that boxes could be “daisy-chained” for additional length when needed.

Monitor System
Stage monitors were handled by Electrotec engineer Bill Chrysler. The Electrotec Soundcraft 32-channel board was driving 13 separate stage monitor speakers, arranged on 10 mixes.

“I’m using the 10 mixes for Roxy Music, so that still leaves me with six discrete outputs for opening acts,” Chrysler offers. “After Roxy’s sound check, I go around to the back of the board and change my output patching; that way the levels I’ve set for Roxy don’t get touched until they come on stage again. Six more mixes is usually more than adequate for most opening acts.”

Chrysler’s 10 monitor mixes for the headline band were set up as follows: sidefills; keyboardist; bass guitarist; lead guitarist; Ferry’s downstage vocal mix; drummer; background vocal; sax; stage-left guitarist; and percussionist. During sound check he was able to speak directly to each stage monitor mix area via the console’s built-in talkback facility.

Monitor speakers were of three types. Sidefills comprised a Lab-Q stack on each side. The keyboard mix was heard through a three-way composite box measuring approximately 3 by 4 feet.

All remaining mixes were driven through an Electrotec single-I5 floor slant, which contains a single 15-inch JBL E130 speaker and a 2441 driver on a 2390 horn/lens attachment (Figure 9). The wooden box has a cutout around the lens that serves as protection for the fragile metal lens plates, while offering unobstructed lateral dispersion at the same time; it also serves as a carrying handle.

Figure 9 (click to enlarge)

Monitor Electronics
Electrotcc’s monitor system features Klark-Teknik DN27 third-octave graphic equalizers, into which have been built the crossover units. Using the DN27’s power supply, each custom-designed card offers bi-amp mix capability with a crossover point of 1.5 kHz. High and low output adjustments are located on the equalizer’s front panel. The system Chrysler was tending for Roxy Music offered these third-octave EQ/crossover units on 12 of the board’s available 16 mixes.

Graphics and other monitor processing gear were contained in three electronics racks, which he stacked on top of his monitor amp racks for quick access (Figure 10). The racks included eight sides of Omnicraft GT-4 noise gates for drum use; according to Chrysler, however, they had not been necessary yet with this show.

Figure 10 (click to enlarge)

One of the system’s more sensible features was a spare power supply for the monitor console located in the same road case as the primary supply, pre-wired and switchable on-line should the need arise. Referring to the monitor system at his disposal. Chrysler says that usually he will adjust the graphic equalizers during Roxy Music’s sound check, and then leave them set.

“I don’t get into changing things just for an opening act—that can jeopardize Roxy’s set,” he continues. “If a mix does not sound right for the opening act with that EQ in-line. I can easily switch it out. Our wedges (monitors) are really quite flat, so that works fine. I can make both acts happy with very little dial-twisting.”

The Electrotec slant monitor is claimed to have a frequency response of 70 Hz to 18 kHz, ±3 dB. A sound pressure level of 125 dB at the listener’s ears is said to be possible with this system. Chrysler’s Electrotec/Soundcraft monitor console offered great flexibility in the EQ department, he says, with its four-band parametric capabilities on each output mix, also switchable in and out of the line.

Output mix levels are displayed on an LED ladder-type visual readout. “I will rarely, if ever, go into the red zone,” he relates. “With the (JBL) 6233 amplifiers, and the crossover line-drivers in the EQ units, I have tons of headroom. The system sort of idles through the show, which is really good; no distortion.”

With the Lab-Q stacks on stage for sidefill speakers, onstage monitor levels were quite high during sound check, yet the console’s LRD displays were consistently percolating 4 to 6 dB below clipping.

Showtime—The Acid Test
Roxy Music presents a musical show that covers a great dynamic range, with the included program material ranging from soft instrumental ballads with alto sax lines, to double-guitar-riffing, sledgehammer rockers. The Electrotec sound system was called upon to respond instantly to level changes of 25 dB or so, and appeared to be remarkably quiet—no “hiss” was present during the softer numbers.

As the show progressed, the louder numbers became almost welcome. The Lab-Q low-end section was capable of punching a lot of air in the 40 to 100 Hz region, which had positive effects on the crowd’s response. One young woman 200 feet or so from the speaker stacks asked me why she could feel.the music’s low notes “in her chest” ... I found it best not to try to answer that one.

(click to enlarge)

The San Diego State University outdoor amphitheater is a venue that usually dispels the show’s low-frequency program material by the time sound reaches the upper regions of the seating area, but the Lab-Q system changed that. The upper half of the amphitheater seating area actually seemed to have a greater bass response than the closer-in front seating rows; a reflection, perhaps, on the three-high stacking of the low-end cabinets, which created strong bass line arrays.

And the high frequencies carried well too—vocal sibilance and intelligibility was excellent, even in the highest seating rows. As stacked in that venue, the Lab-Q speaker system arrays did indeed have a high “Q” (directivity factor). As I walked the upper perimeter from left to right, it was possible to tell when I was directly on-axis with the center of each stack of three cabinets.

However, the transitions were smooth, and an untrained ear would not have noticed the hot spots. All told, an excellent outdoor speaker system that would almost certainly perform just as well in arena situations.

The Electrotec Lab-Q system also was servicing Bob Seger, Alabama, Rick Springfield, John Cougar, and Tom Petty as this article is being written. Concert sound engineers would find a visit to one of these shows well worth a listen, since, to this writer at least, the new Lab-Q speaker system represents a qualitative improvement over the company’s older component sound system.

Editor’s Note: This is a series of articles from Recording Engineer/Producer (RE/P) magazine, which began publishing in 1970 under the direction of publisher/editor Martin Gallay. After a great run, RE/P ceased publishing in the early 1990s, yet its content is still much revered in the professional audio community. RE/P also published the first issues of Live Sound International magazine as a quarterly supplement, beginning in the late 1980s, and LSI grew to a monthly publication that continues to thrive to this day. Our sincere thanks to Mark Gander of JBL Professional for his considerable support on this archive project.

Read more RE/P Files here.



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RE/P Files: Electrotec’s System For Roxy Music, August 1983
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