How rock concerts work

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The speakers used in rock shows have changed significantly over the years, and concert sound has gotten a lot better. Concert engineers used to stack loads of large speakers on top of one another to get the volume they needed. But the sound that all those speakers created was not unified, so the music could turn out radically different in various spots around the hall.

Without a sound system, you don't have much of a rock concert.

At most medium to large shows you attend these days, you’re likely to see a big vertical bank of speakers hanging high up on each side of the stage. This is called a line array. Each of the identical PA speakers in the line array contains high-, medium- and low-frequency drivers (speakers). When the speakers are stacked close together and exactly on top of one another, all the low-frequency speakers in the array line up; the same thing goes for the mid- and high-frequency speakers. 

This arrangement allows the speakers in the line to work together to make a single, unified sound. When the lines of low-, medium- and high-frequency speakers are working together, they collectively fill out the entire frequency range of the music being created on the stage, and deliver it to large areas of the room. 

The number and placement of the speakers in the array depend on the unique design of the venue. A smaller array of PA speakers might be appropriate for a medium-size hall, while a much larger array might be suitable for a big outdoor festival. 

Video production

Video has become a huge part of the concert experience, often making the onstage performance seem like just one component of a music video being presented live. In fact, the video system usually consumes more electricity than the light show or the sound system do. Editors piece together video footage of all kinds (pretty much anything you can imagine) to correspond to the assorted songs, sections, moods, or moments in the band’s set. The video you see above the stage can sync up to the backing tracks and the lighting system via MIDI or SMPTE code.

Celt-rockers U2 have pushed the live rock video concept further than any other major act. Instead of preparing all the video beforehand, U2’s video team shoots live video at the concert itself. During every show of the band’s 2009 “360” tour, the U2 video design group created original visual graphics using live video footage shot on 15 cameras positioned throughout the stadium. They also brought 120GB of prerendered video to intersperse with the live video during each show.

But U2 wanted more. Dell provided some powerful laptops that the U2 video team used to create original video on the fly, on the road, much of it related to current news events, or to local news in the city where they were playing.

Dell’s Chris Ratcliffe, director of solutions and services marketing, accompanied U2 for many dates in the "360" tour, and worked closely with the tour’s video director, a man called “Smasher.” Ratcliffe hooked Smasher up with an M6400 (later an M6500), on which he created original video using Adobe Creative Suite, Autodesk Maya, and other programs.

Ratcliffe says Smasher was able to create new video while sitting at a coffee shop in the morning, and then dump it onto a thumb drive and transfer it to the show's video servers for presentation on the big screen that night. Those video servers—a set of three Dell Precision R5400 rack-mounted workstations—were also provided by Dell.

 During the "360" tour, the band played underneath a huge circular video screen designed by British engineering firm Buro Happold. The screen weighed 54 tons, measured 4300 square feet when closed, and expanded to over 14,000 square feet and 7 stories tall when opened.

The light show

In modern rock shows, the lights on the stage move around and point at different places on the stage. Older PAR64 “light cans” are sometimes used in concert with electromechanical lights. An engineer controls the movement of the lights, as well as the light colors and levels, from a lighting board that is usually located near the main mixing board out in front of the stage.

Older light boards were little more than a box with a bunch of dimmer switches united in one place. But modern lighting consoles (such as Jands Vista models) are powered by computer chips and are fully programmable and automated. They can control the projection of LED light images, all stage lighting, video, and even pyrotechnic effects. Many boards have faders, as well, so that the operator can control all lighting effects in real time. 

More often, however, the lighting for a concert is all preprogrammed in the light board by the light-board operator and the lighting designer. This lighting program is programmed onto a timeline that displays on the lighting console or on an external monitor.

The timeline on the light console adheres to the same MIDI Show Control (MSC) or timecode (SMPTE timecode) that the soundboard runs, so the two systems can easily link together and synchronize, along with the digital audio workstation (usually Pro Tools) that might be playing the backing tracks. For instance, a sudden flash of brilliant light can be programmed to coincide perfectly with a sudden, dramatic crescendo in the music, creating an exciting sensory experience for the audience.

Of course, the mixing engineer, the monitor engineer, the video director, and the lighting engineer must all communicate with one another before, during, and after the show. Usually they accomplish this through walkie-talkies, via a hardwired intercom system, or by way of a mini wireless network custom-designed by one of the wireless carriers.

This story, "How rock concerts work" was originally published by TechHive.

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