Technology Tweaks Enhance Audio Monitoring in Trucks

When it comes to monitoring audio for sports broadcasts, not a lot has changed in basic loudspeaker design in recent years, thanks largely to the annoyingly immutable nature of physics. What is changing, however, at least when it comes to putting those speakers into remote trucks, is the array of choices available and the proliferation of technologies that will help tweak those physical limitations a little. The small size of most mobile audio studios and the engineers’ demand for monitoring diversity means that two trends are on the rise: more auto-calibration options will soon become available, and more brands will enter the market.

According to Group One VP of Audio Chris Fichera, Blue Sky speakers, distributed in the U.S. by Group One, will add auto-calibration to broadcast-loudspeaker offerings later this year. “There’s no room for multiple monitors as you would have in a regular control room, and there’s no budget to hire acousticians to calibrate speakers and design acoustics most of the time,” he says. “I don’t see that changing, so the logical thing is to add auto-calibration capability.”

Several monitor brands, notably Genelec and Dynaudio, already offer integrated DSP for automatic room calibration.

Although Blue Sky monitors have gained traction in the mobile-broadcast sector in recent years — ESPN now specifies them for its trucks — Fichera knows what it’s like to try to bring a new brand into a broadcast market sector: Group One sells DiGiCo consoles, which, like German entries Stagetec and Lawo, have been trying dislodge market dominator Calrec.

Another German company, microphone manufacturer Neumann, has managed to make significant headway since introducing its KH 120 nearfield monitors to the U.S. market at the October 2010 AES Show, via Sennheiser. Paul Bonar, VP of engineering at mobile-unit provider Game Creek Video, says the KH 120s were used for two new trucks that Game Creek recently finished for NFL Network: Pride and Glory.

“The Neumann speakers are a good choice for mobile units,” he says. “Besides sounding great, their size and shape make designing and implementing a layout and a mounting scheme much easier than some other monitors.”

Bonar notes that, in several trucks, the speakers’ smaller size allowed the control room to include a 15-in. video monitor for non-delayed program content. That monitor is also used for lip-synching and, since it’s substantially larger than the usual 9-in. screen used for that purpose, makes the sync work much easier.

“The size and shape of a speaker can make a big difference in other aspects of the truck layout,” he says. “It’s not just that it has to sound great; it’s got to fit the mobile environment as well.”

Genelec speakers remain a favorite for remote-truck monitoring; the brand was a pioneer in self-calibration technology with its Auto-Cal software. However, changes to its loudspeakers’ enclosure design, particularly implementation of a rear-firing port on its 1030A speakers, can pose a challenge for some truck designers. Bonar says he creates and keeps templates of mounting techniques from different projects to help him determine the best mounting angle that still allows the port to fire properly. “It’s a great speaker,” he says, “but you have to be careful how it’s mounted in a truck environment.”

Problems with the rear port and mounting are “by and large, just myths,” says Genelec Marketing Director Will Eggleston: “As long as there is a space that’s at least 2 to 4 in. between the back of the speaker and the closest reflective surface, that’s all the clearance needed.”

In addition, he points out, the port on ported speakers isn’t fixed in terms of its output.  Rather, the sound-pressure level it emits is inversely frequency-dependent. “The contribution of the port in terms of SPL is greatest at the [low-frequency] cutoff frequency,” he explains. “As the frequencies increase, the contribution of the port diminishes pretty rapidly up to almost [double] the tuning frequency, where its contribution is nil. And if [the loudspeaker] is being used with a sub, then the rear port isn’t typically being used at all.”

Eggleston adds that a rear-ported speaker offers significant benefits in the form of front-baffle waveguide geometry in situations where subs are not used and that most truck-wall designs offer sufficient clearance to use them.

But his points underscore the balance that monitors used in remote trucks have long had to strike in shape, size, functionality, and performance. And a wide spectrum of subjective opinions among engineers means that a diversity of brands and types will have to be accommodated: in addition to Blue Sky, Genelec, and now Neumann, such brands as ADAM and Tannoy remain popular with certain truck users.

The complexities of monitor-speaker performance in acoustically constricted spaces assure that this will remain a topic of debate. The important thing many broadcasters are in agreement on is that the conversation is taking place more often these days than in the past.