Someone wrote to me last month asking about the term "ACL." He asked why a lot of new moving lights were being touted as moving ACLs. Outside of the lighting industry, they would think we were referring to a ligament in the knee.
To those of us who work in the lighting industry, it's a type of lamp called an aircraft landing light. They are manufactured for airplanes and they produce a very tight collimated beam of bright white light. They were designed to illuminate the runway in front of the plane when it's landing. But somewhere along the line, it ended up in a PAR can.
Love Those Lovos
Lamps are designed to run at different voltages. A flashlight bulb may run off a couple volts DC while most airplane lamps run on 13 volts. In the theatre world there is a term for lamps that require less than 120 volts to illuminate to full – "lovos." I have found old theatrical lovos in textbooks going back to the 1930s. The original lovos were in Fresnel fixtures and some appeared in strip lights. Today, most lovos are PAR (parabolic aluminum reflector) lamps. They have a tungsten filament mounted in front of a reflector, then sealed air tight behind a lens.
If you apply 120 volts to a low voltage lamp, it will blow up. So the idea is to wire a bunch of lamps in series, as opposed to parallel, so the voltage divides equally among all the lamps. If you plug a few lamps into one quad box or power strip, you are running them all in parallel. But if you connect them by wiring the second terminal of the first lamp to the first terminal of the second lamp, the second terminal of the second lamp to the first terminal of the third lamp, and so on until you've connected all the lamps, then they are wired in series. If you wire four lamps in this manner, each lamp would only get ¼ of the applied voltage, or approximately 28 volts, depending on the applied voltage.
At many concerts you will notice bright lights fanned out in an array, simulating fingers of light. They are not illuminating anything in particular, they are lighting air artistically. Most likely these are ACLs. Who came up with the idea of putting these lamps in PAR fixtures? There are no textbooks or Internet sites that could answer this question, so I went to some of rock ‘n' rolls' greatest lighting legends in search of information about who was responsible.
Enter Stage Light
Bob See is the proprietor of See Factor Lighting, a major lighting vendor located in New York City. He started his career as the house electrician at the Fillmore East. I picked his brain about the use of these lamps back in the early 1970s.
"The first time I saw lovos used," he said, "was at a Jefferson Airplane concert. Chip Monck (legendary pioneer of concert lighting) had built some smaller replicas of a [Boeing] 707 plane out of wire and attached some PAR 56 lovo lights and small police beacons to them. At the opening of the show, Chip flew the two planes over the crowd with lights ablaze as the Joshua Light show had some 707 airplane footage projected on a paper screen upstage. A hundred and thirty decibels of jet noise came out of the PA. As the planes reached the stage, the band stepped through the paper screen, making their entrance."
Later on, Bob teamed up with Howard Ungerleider in his quest for the perfect beam of light. Howard designs the lighting for several bands and is world renowned for his 30-odd years of work with the band Rush. Howard told Bob he was searching for a truck-style lamp that could project a perfectly collimated beam of light that he could place in a PAR. The light beams from PAR 64 lamps are typically oval-shaped. But he wanted the beam to stay tight, like a searchlight, and not expand over distance. Bob had noticed that the beams in the police beacons he rented from Times Square Lighting for the Airplane shows did this. They were lovos.
So around 1973, Howard attended a military auction in Washington, D.C. with his friend Bill Pace, who was the LD at a club called The Bayou. They came upon some old, large marine beacons. Howard noticed the bright thin beam of light that Bob had seen as well. He ended up buying a case of the lamps used in these fixtures and returned to New York. He and Bob took one of the lamps and, lo and behold, it fit in the PAR fixtures, retaining ring and all. He wired them in a series and saw the future of his lighting designs.
All For One
Back then, there was no Internet, but Bob had a collection of lighting catalogs. After a considerable amount of searching, he found a GE catalog with lamps made for airplanes. He found some 250-watt, 13 volt PAR 64 lamps and ordered them. Howard needed to use eight of them connected in series on one 2k dimmer.
"The problem," Bob said, "was that if one bulb blew, you ended up losing all of them. We were going through a ton of bulbs. Eventually I found the 28-volt version of this bulb, and we only needed to series four of them together."
This meant he only needed 1k dimmers and smaller gauge cable to fire them up. Thus the infamous 4-light bar of ACLs was born. Eventually people used brighter 600-watt versions of the lamp. For some reason, these lamps never flashed on as quickly as the 250-watt ones, thus they never became the norm in concert lighting.
Vectors and Fingers
Howard claims that his friends at Atlantis Lighting in Virginia were the first people to use the ACLs live in concert, on a Little Feat tour, circa 1973. But as Bob says, "At this time, everyone was trying to one-up each other with the next cool light source in a new fixture. Howard left it to me to search for what he wanted."
Soon Howard was using hundreds of these fixtures on Rush tours. It became popular for him to actually name his ACL focuses. Terms like "fingers of death" and "vectors" became common. Howard used so many ACLs in his lighting rigs that he eventually had Bob build special 28-volt dimmers just so he could turn the lamps on individually. Paul Edwards was hired to build a special console, exclusively for Howard to be able to write chases using individual ACL lamps on Rush's Power Windows Tour in 1985.
ACL lamps are still used today, but things have progressed in lighting manufacturing. Lamps like the ray light came on the scene to replace them. Now moving lights which have nothing to do with low voltage are branding themselves as ACL fixtures simply because they have devised a way to get the same tight beam using special reflectors and lenses.
