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The blog is being migrated and merged with multiple Imphenzia blogs so the format and content will be inconsistent for a while.

Recording Fireworks

mineField recording is fun but also challenging. A while back I posted a comparison of microphones and stereo techniques. I thought I would add some details about the day I recorded that material which was on new years eve when I decided to give it a go to record some isolated fireworks going off. I purchased an assortment of about $400 worth of consumer rockets and shells.

Scouting Location
The day before recording I needed to find a location. Setting off fireworks in Sweden is restricted to new years eve unless you have specific permissions so I wanted to take advantage of that and record it when most people were expecting fireworks to go off. I had purchased a fair amount of fireworks that would take some time to set off, I expected it would take a couple of hours or so I wanted to find a place that was far away enough from residential areas but still accessible by car.

Sennheiser ORTF and Schoeps M/S Comparison


Photo from Fireworks recording session
I have become somewhat comfortable with different stereo techniques even though I still have very much to learn and even more to master. I took the opportunity to purchase a variety of fireworks and rigged an array of microphones in a somewhat remote location while it was still daylight on new years eve. In total I brought 10 microphones that I placed in different stereo and mono configurations ranging from a fairly close distance of 25 meters, to a remote distance of 100 meters.

It will likely come a time when I write a full post about the fireworks field recording session but for now I'd like to focus on two pair of microphones in particular; a pair of Sennheiser MKH 8040 cardioid microphones arranged in the ORTF (Office de Radiodiffusion Télévision Française) stereo configuration, and a mid-side (M/S) setup consisting of a Schoeps CCM41 supercardioid and a Schoeps CCM8 figure 8 microphone.

ORTF


Most of my stereo recordings so far have been ORTF recordings which is probably the simplest configuration to grasp. Basically, it is two identical cardioid microphones that are spaced 17 cm apart and angled 110 degrees from one another, which sort of mimics the way human ears work. The upsides to this configuration is simplicity and a nice realistic stereo width to the sound. The downsides, on the other hand, are that 1) there is no microphone pointing straight ahead so a good mono recording in center field will be missing, 2) there may be phasing issues when the stereo recording is mixed down to mono (i.e. the left and right channels may be cancelling each other out to some extend since the microphones are spaced apart) and 3) the stereo width is final, you can't really make it narrower or wider by post processing.

stereo_ortf_sennheiser

Despite its downsides, I like ORTF because it sounds great for stereo ambiences which is mainly what I use it for. In such cases I rarely require a mono channel facing forward (e.g. forest, beach, city, public places) and to avoid phasing issues all together, for a good mono sound, the simple solution is to just use the left or right channel single as mono.

Video: Pitch Shifting and Microphone Specs

The other day I broke a laptop monitor in half and I recorded it using four very different microphones with different specifications. I recorded the sounds with a sampling rate of 192 kHz and loaded the sounds into Izotope RX5 to show the spectrogram and pitch down the sounds two octaves. This video demonstrates how different the sounds are when pitched down since some of the microphones capture audio well beyond what the human ear can hear - yet when you pitch the sound down those inaudible frequencies are brought into our range of hearing:



Microphones Used:
Sanken CO-100K (20 - 100'000 Hz)
Sennheiser MKH 8040 (30 - 50'000 Hz)
Rode NTG3 (40 - 20'000 Hz)
Schoeps CCM41 (40 - 20'000 Hz)

Recorder:
Sound Devices 788T

Software Used:
Izotope RX5