A/V Systems at Indianapolis Motor Speedway Mix Old and New

Dave Dusick, owner of Racetrack Engineering, the A/V-systems manager and troubleshooter for auto racing, was holding a meeting in a corner of the cafeteria in the media building, next to the Indianapolis Motor Speedway’s iconic infield Pagoda. He was talking his crew of a dozen men and women, some working their first Indianapolis 500 race, through their responsibilities, often reminding newbies and veterans alike that anything can happen, and often does.

The caution flag came out early the next day during the race’s opening ceremonies, when 80-year-old Mari Hulman George, in the middle of uttering the command “Ladies and gentlemen, start your engines!” that officially starts the Indianapolis 500, was unexpectedly — and rather loudly — joined by her daughter.

Such gaffes are part of the Indy 500, where plenty of mistakes take place on the track, often with catastrophic results, and this year started happening well before the day of the race. But Dusick takes it in stride. After all, he has worked around Indy cars a long time, having started as an intern at the IMS right out of college in 1996 and, several years later, founded Racetrack Engineering, which counts IMS, the Pirelli World Challenge, and F1 track Circuit of the Americas as clients.

“There are lots of intricacies and agendas in auto racing,” he says, “and my job is to make sense of them.”

One of those intricacies has been the IMS’s sound system. For years, the hundreds of speakers atop poles ringing the infield were ancient Western Electric horns, narrow-band transducers whose truncated frequency range of roughly 300 Hz-3 kHz was perfectly matched to the range of the human voice, giving them the most sought-after characteristic in a noisy environment: high speech intelligibility. But the horns’ limited range became apparent as the race’s events began to incorporate music two decades ago, a trend seen throughout sports venues.

Dusick approached this challenge as he does all of them: “I know race tracks; I don’t know acoustics. So I find the right person who does.”

In this case, that person is Steve Durr, a Nashville-based audio-systems designer and acoustician who has carved a niche in sports-venue sound, designing systems for the Kansas City Chiefs and other teams. Together, Durr and Dusick work with a hybrid speaker system that, since 2005, has included customized full-range speakers weatherized for outdoor use that Dusick had commissioned QSC to manufacture.

At IMS, they enumerate each of the more than 690 speakers on the poles and elsewhere in the venue used for the PA — Dusick says he still discovers speakers that may date back 60 years or more — on a QSC speaker DSP program. This has enabled Durr to calculate the optimal equalization parameters for each pair of bi-amped speakers, using a White graphic EQ.

Dusick shows the DSP display to a visitor in the track’s Phone Room — the core of the venue’s A/V-signal–transport system, all of which still rides on a copper-based infrastructure (and whose handwritten maintenance logs predate the Nixon administration). Scrolling through page after page of speakers, he points out how each grouping has its own EQ curve.

“The big challenge is that the grandstands have been built over the course of a hundred years, so the poles and the speakers are at very different distances from the seats, depending on where on the track you are. Some seats are as close as that to a speaker,” he explains, pointing to a wall 3 ft. away. “Other grandstands have the back row 80 ft. high and parabolically curved. The goal was to make the sound as consistent as possible for all of them.”

So, along with equalizing the speakers for a timbral compromise between music and speech, Durr also used the DSP to balance each speaker pair’s level so that anyone sitting in the middle row of any grandstand configuration anywhere along the track’s 2.5-mile length would hear the sound at the same volume. It was a tedious undertaking that Dusick says required both an SPL meter and Durr’s ears — measurements both objective and subjective — to ensure that level consistency applies to both speech and music.

That first took place in 2007, when Durr came aboard. Now, when he returns each year to tweak the system and mix the live sound for the opening ceremonies and PA commentary during the race, he has to coax the system back to life.

“It’s used only a few times a year. It needs time to warm up,” he says. “It’s just sitting there for nine months at a time. Sometimes, we find animals have built nests in the speakers.” Warming them up includes firing up 10,000 W of Crown amplifiers (connected by fiber cabling to 14 amp-room locations around the track).

Race Control
If the PA system is a study in mixing old and new technology in a challenging environment, the track’s Race Control center is a study in technical modernity. Also managed by Racetrack Engineering, it features a video wall segmented vertically into five rows, the first four rows taking in 36 feeds on fiber cabling from the broadcast cameras (the fifth row monitors the track’s PTZ security cameras). Replays on them are used by IMS officials to rule on possible infractions during the race and to investigate crashes. Input from the broadcast cameras is archived to six Evertz Microsystems DreamCatcher replay decks.

Race Control also takes in real-time communications from spotters positioned along the track and calling in warnings about problems too nuanced even for an HD camera to pick up, such as debris on the track. The spotters can also go beyond the visual. “They might call in, ‘Car 12 in turn three smells funny,’” says Dusick, underscoring that all five senses are needed to avert disasters.

“You never know where the next one is coming from,” he says of the challenges that face the track’s A/V systems. “What we do know is that, no matter what, we’re going to have to fix them.”

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