Son Doong, also called the "Infinite cave" because of its massive size, was discovered by a native of the area in 1991. However, as the entrance to the cave is as unobtrusive as it is steep, it took him until 2009 to actually relocate the cave in the jungle and explore it with a group of British scientists. The 5k long cave features huge chambers - some of them up to 180m high, stalagmites formed over millenia, a fast river flowing through the cave, phytokarst and lush, green vegetation at the points where the cave's ceiling has collapsed.
Martin Edström first heard about the cave in 2014. Curiosity piqued, he started researching further and then heard news that the pristine caves were being considered for possible exploitation for tourism. Martin decided to capture the almost untouched beauty of the cave and preserve it in a 360° story and a photo archive for National Geographic. "I hope that our documentation of Son Doong will not only help tell the story about this cave, but also preserve a kind of digital copy of the cave - making sure we can visit it digitally whatever happens to it in the future," says Martin.
Martin moved fast: on securing National Geographic and a group of sponsors to support an expedition to Son Doong, he established a team of six and quickly started planning their trip. "Basically, we had just little more than two months to arrange for everything. The logistical effort was enormous. To give you an idea, we had about 300 to 400 kilogrammes of technical gear to take to Vietnam and drag around with us, cameras, lots of lighting, tripods, you name it. This is excluding tents and food and the like. We had fantastic help from an expedition team in Vietnam to arrange these everyday expedition logistics."
Martin was joined by Erik Hinnerdal and Mats Kahlström, his two assistant photographers who would also capture sound, Fredrik Edström for communications, Alfred Runow for logistics and field assistants Katja Adolphson and Sebastian Zethraeus, who were tasked with meticulously lighting up the cave in 360° to allow the wonderful photos to be taken.
The microphones selected by Martin and his team for the expedition were an SPM 8000 stereo microphone, an MKH 8060 short gun microphone and an MKH 8070 long gun microphone. All three of them are based on Sennheiser's MKH 8000 series radio frequency condenser microphones, which feature a very natural sound with extremely low inherent self-noise and high resistance to unfavourable climatic conditions, such as moisture, dampness, cold and heat.
Martin and his team spent two weeks in Vietnam and about a week inside Son Doong cave. Meanwhile, the original team had been expanded by guides and porters and counted about 50 people. Martin recalls, "We spent five very concentrated days in the cave photographing and recording. The biggest portion of this time was taken up by lighting the cave properly, as Son Doong is so enormously big. Sound-wise, there was always something to be heard: wind, water dripping, a river running, distant birds and sometimes also the thundering silence, if you know what I mean!
"The SPM 8000 stereo microphone was always on recording duty, it was great for capturing the atmospheric audio. We used the MKH 8060 short shotgun microphone about 50% of the time, when we wanted to highlight a sound, for example the singing of birds, or some sounds of the river t
