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.


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.


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.

Powerboat passing by to game-loop audio

This year I went to the Nynäs Offshore Race which takes place only a 30 minute walk from my home in Nynäshamn. I brought my new "field recording kit" that may not be the most portable setup in the world, but it gives me the best option for recording directional spot mono audio using a Rode NTG3 shotgun microhpone and environmental ambiences and stereo effects with a pair of Sennheiser MKH 8040 micorphones. The mics are housed in wind-protecting Rode and Rycote blimps with dead kittens (those huge furry things to block most of the wind.) I record the 3 channels of audio into a Sound Devices 633 field mixer at 192 kHz 24 bit audio.

I recorded quite a few powerboats as the passed by - but getting usable game audio is quite tricky. I'll tell you why:

First of all, there is a PA system with an announcer that feels obligated to speak non-stop which is great for the audience but terrible for someone who wants to capture the boats and nothing else. I had to find a spot close enough to the boats, but far away enough from the diesel-powered speakers pushing out a distorted commentator voic.

Then there is the audience, they tend to chat and cheer a lot so I had to find a spot far enough away from most of them - luckily the powerboats are loud so the gain is not set too high which reduces the chance of spectator voices.

Another challenge is that you don't really get that close to the boats, they have to drive where it's deep and safe enough which isn't always that close to land.

The splashing water is another parameter to consider, but again, not loud enough to be too great of a problem.

The biggest problem, however, is that the boats pass by producing a sound that fades in and out and shifts in pitch due to the doppler effect. By default they will be great if you want to have the sound of a passing powerboat - but you could never apply that sound to a boat in a game since it simply doesn't loop well.

Turning the passing powerboat sound into looping game audio

I put together a video where a single powerboat passing by is turned into a short loop of game audio that could be used on a powerboat. If you need to do something similar, or if you are just curious what work goes into converting the sound, have a look:

I ended up using the audio from the Rode NTG3 shotgun mic this time since I didn't need it to be stereo and it produced the longest sustainable sound as I aimed the microphone at the boat as it passed by. It also contained the least polluted sound since the design of the shotgun mic blocks off-axis sounds fairly well.

This sound loop, among many others, will be included in the next update of the Universal Sound FX library.