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.

My first convolution reverb recording...

A while ago I started experimenting with convolution reverbs. Convolution reverbs are reverbs which "sample" the reverb of a given space. This is amazing technology as you are able to sample any physical space or even any old outboard equipment and replicate the reverb characteristics within your audio software.

Owning several convolution reverb plug-ins, I wanted to experiment with recording my own spaces. My first recorded convolution was recorded using the Waves IR1. Starting with baby steps, my first recording was of course a bathroom. I couldn't believe how quick and easy it was, and how realistic it was!



From the photo you can see an omni direction mic set up at the far end of the bathroom, and a speaker on the left hand side. From my studio I generated a frequency sweep which played through the speaker - and was captured using this microphone and recorded in Pro Tools. This new file of the recorded sweep was then loaded and analysed by Waves IR1. Within a few seconds of analysing, IR1 created a new convolution pre-set of the bathroom! After running some dialogue through this setting I couldn't believe just how well IR1 cloned the bathroom reverb!

I can now see myself recording many, many rooms and old reverb units as this is simply amazing!