Recording Cave Convolutions

After being bitten by the "convolution" recording bug, I wanted to set a new challenge. My mission was to record the convolution of a cave! After all this sounds like fun.., doesn't it? Well yes in theory... One of the most difficult parts of convolution recording is the powering of the speaker(s) for playback of the frequency sweep. In the case of this cave another challenge loomed as there was also quite a walk into the caves. Being by myself this meant the carrying of quite a lot of gear- and at times in confined squishy spaces. Admittedly I was primarily there to record cave atmospheres, however since I made this an entire day trip I decided to take the extra gear and capture some convolutions whilst had the permission, time and opportunity.

My convolution recording set up included a pre made ProTools session (sine wave sweeps and record tracks labelled and spaced) running off a MacBook with an MBox mini. This allowed me to be able to have playback as well as a recording device all in one- with headphone monitoring. I then placed a powered speaker inside a large chamber in the cave. Because I had ProTools set up before hand, I set up my session to playback along the timeline with the sweep every 30 seconds. This allowed me with my handheld stereo field mics (plugged into the MBox) to walk around the cave and record many perspectives without having to stop and start. The cave was cold and very damp so I didn't want to take any longer than necessary.

The picture above shows my basic laptop set up with the speaker set up behind in the top left hand corner. The mics as mentioned were hand held as I walked around the space. I had a Rode NT4 mounted into a Rycote blimp.