Mixing Crystal clear sound from a mile down!

Naica, Mexico – December, 2009. Philippe Mercier, a Sound Mixer from Montreal, Canada, got a call to mix sound for a
National Geographic documentary focused on the “Cueva de Los Cristales” (Cave of Crystals) in the Chihuahuan desert of
Mexico. He expected to work in heat, however the extremely high temperatures and 100% humidity of the subterranean Naica
mine can kill man and machine within minutes. Thus, very defined work flows to protect both the crew and equipment were
necessary. Preparation and fulfillment of this job would be like no other.

Crews mining for lead and silver far beneath Naica mountain discovered the Crystal Cave in 2000. They were stunned by its beauty and amazed at the tree-trunk sized crystals of Gypsum they saw reflecting throughout the cave. In an effort to share this yet untold story with the rest of the world, an international crew gathered with state of the art, humidity-defying equipment to document scientists in their expeditions into and around the cave.

Prior to departure, Mercier visited Trew Audio in Toronto and rented a Sennheiser MKH50 and a sync generator and purchased Aquapacs to protect his wireless units from moisture.

I recorded Naica on my Zaxcom Deva 5 recorder. We used Audio Limited 2020 wireless kits with high gain antennas. We also
rigged the cave with some Sanken cs3 shotgun microphones to capture the cave ambience and natural echo. Scientists were all
wired in their hard hats using Sanken cos-11 lavalier microphones, and we used aquapacs to protect the Audio Limited transmitters
that they were wearing under their space suits. These aquapacs kept the Audio transmitters air tight, dry and functional. We
[made] a decision that the talent’s hardhat would be wired and would have the freedom to walk around in the cave without sound
issues.

The film consisted of a 12 day expedition showing 4 scientists exploring the crystal cave for 20 minute missions 3 or 4 times
a day. Our job was to record dialogue at all times before during and after the entries. 2 film units–one filming inside the
cave and the other in mission control. A total of 6 high definition cameras were used to capture all the action.

The set was separated in 2 sections:

Mission Control: with temperature reaching 45 C. / 113F. 75% [humidity]. Mission control is the corridor leading to the crystal
cave where you find all the technology that keeps you alive. Industrial fans, dressing room, preparation area, medics, computers,
liquids and the most appreciated by everyone ice cubes (air conditioned cold tents.) This is where my audio gear chilled between
missions.

The Crystal cave: Temperature reaching 55 C. / 133 F. 100% [humidity].
Unstable grounds, edgy terrain, intense heat, mind blowing!

Recording in an environment like Naica was a privilege, a great personnel challenge and also a good testing ground for production
audio gear.

Philippe Mercier