A Sennheiser MKH 418 M/S stereo shotgun microphone captures the recent Space Shuttle launch in glorious stereo.
CAPE CANAVERAL, FLORIDA - DECEMBER 2009: Florida-based multimedia company Road Kill Creative (RKC) captures high-fidelity sound for use in radio, TV, video games, and sound effects libraries. When asked to deliver a hi-fi recording of a space shuttle launch, they were shocked to learn that, although NASA now captures each launch in full HD video, the audio system at the Kennedy Space Center traces back to the (monaural) Apollo days! After six months of negotiations with NASA, RKC engineer Chris Pendl recorded the launch of space shuttles Atlantis and Discovery in glorious stereo using a Sennheiser MKH 418 M/S stereo shotgun microphone.
The MKH 418 endured sound pressures in excess of 150 dB, two Florida rainstorms, and literally days in the sun and salt air. Remarkably, after less than a week of "dry time," the microphones captured audio that was indistinguishable from that of an MKH 418 that had stayed home!
After conferring with Dawn Birr, Sennheiser's product manager for professional products, who convinced him the MKH 418 would work, Chris then successfully persuaded NASA that the 21st century was ready for a stereo recording of their greatest public relations endeavor. Site security gave him the opportunity to place his microphone 400 feet from the launch pad for his first recording.
The situation left him with a number of challenges to overcome. First, the mic position would certainly be exposed to tremendous SPLs, smoke, and drenching water-either as part of the launch itself or as part of the cleanup that occurs immediately after the launch. Because the site is secured 24-hours in advance of the launch, he would have to situate the microphone and let it set for a night and a day in the baking sun and salt air of maritime south Florida. Lastly, his Sound Devices 702 digital recorder would be tucked away in an Apollo-era bunker, so he would have to guess at levels and use a pre-programmed record and stop time.
The monaural microphone that NASA uses is expressly built to endure the launch-site conditions. Fidelity is an afterthought. Could any high-fidelity microphone survive the launch? Pendl contacted Sennheiser to determine if his MKH 418 would make it. The MKH 418 uses a "mid-side" (M/S) arrangement of supercardioid and figure-8 capsules to deliver rich stereo separation.
Its stated maximum SPL is 130 dB. Sennheiser was confident that the microphone would more than survive - it would thrive!
"On the day of the launch, I was the odd-man-out among NASA's multimedia team," Pendl recalled. "They were pretty merciless. They kept telling me stories of other microphones in a similar situation that had been completely destroyed. They talked about all the dead animals that they pick up after the launch - killed by the concussive blast. Indeed, the closest people to the launch, after the astronauts, are two miles away! I took a pretty good ribbing. After it was all said and done, they brought the MKH 418 back to me and literally poured water out of it at my feet."
But Pendl's immediate concern, the recording itself, was spectacular. His guess at gain was pretty good, and with high signal-to-noise from the Sennheiser shotgun and the recorder's 24-bits of resolution, the normalized version was perfectly clear and robust. "For the loudest few seconds of the launch, the capsules overloaded a bit," said Pendl. "But it's pretty minor and easily ignored in the context of everything else that's happening sonically at that moment. And really, this was approximately 25 dB over the stated maximum SPL! It really hung in there!"
When Pendl sent the recording to NASA's multimedia team, the first thing they asked was whether he had sweetened it, which he hadn't. "They had never heard it so clear," he said. "The stereo separation is stunning. You really feel like you're standing in the middle of the launch! I've listened to it hundreds of times, and it doesn't get old. The recording is so gripping and vivid. I've never heard another recording that even approached it!"
After drying out for a few days, Pendl did a blind comparison between his MKH 418 and another MKH 418. "There was no difference," he reported. "They sounded identical. After all that, the capsules are still in perfect shape!"
Thrilled with the result, NASA invited Pendl back for a second recording.
"Since I already had the close perspective in the bag, I went for two other perspectives, this time with two Sennheiser MKH 418," he said. "But you can't set your watch by a shuttle launch... because they now have to rendezvous with the space station, the launch window is just minutes, and the weather and the equipment have to be absolutely perfect." Pendl set up and took down the microphones several times (a three-hour drive from his home each way) before a scheduled launch turned into a successful launch!
Again, because the mics needed to be in place 24 hours before the launch and because so many launches were scrubbed, the MKH 418s ended up spending day-after-day in the 90-plus high humidity of Florida. In addition, they endured over six cumulative hours of torrential rain and the corrosive coastal air.
"NASA has an interface plate for their communications equipment made of stainless steel near one of the most recent mic positions," said Pendl. "The salt air had completely corroded it! After all that punishment, the mics again A/B'd as indistinguishable from MKH 418s that never left the shop! It was really surprising not just that these mics held up, but that they held up perfectly!"
Sennheiser is a world-leading manufacturer of microphones, headphones and wireless transmission systems. Established in 1945 in Wedemark, Germany, Sennheiser is now a global brand represented in 60 countries around the world with U.S. headquarters in Old Lyme, Connecticut. Sennheiser's pioneering excellence in technology has rewarded the company with numerous awards and accolades including an Emmy, a Grammy, and the Scientific and Engineering Award of the Academy of Motion Picture Arts and Sciences.