July 30, 2014

Road Trip Special: Explosives and Fireworks

Our last full day in South Carolina was a big one! This is the one we planned for. Explosives and guns! Let’s talk about the explosives first.

I’ve recorded explosions before, so I sort of knew what to expect. I also knew it was going to require a lot of planning if I was going to come out with anything worth using. The things I needed to consider were location, gear, and available ordinance. Also, I had to stay within my budget with all of this.

First, I decided to find a location. The main reason we travelled to South Carolina was because of this location. We were given access to this huge farm that was in the middle of nowhere. It made getting great sounds a lot easier. Yes, the sounds we were recording were very loud, but in order to properly capture all of the reverb tails and late reflections, we had to have a quiet location. Of course, there are always birds and bugs, but we can talk about those later. So we had our location.

Next was ordnance. Since I don’t have any fancy licensing, and I couldn’t afford to pay anyone licensed to come out with me, we would have to stick to the small stuff this time. Luckily we know some people who know some people, so we were able to get our hands on a few pieces that were less than legal in most states (but in SC, pretty much anything goes…). We also picked up some fairly standard fireworks for good measure.

Finally, I needed to figure out what gear I was going to use. I decided to set up 3 recorders (744Ts with 302 mixers) – one for the close range mics, one for the mids, and one for the distant mics.

The pressure of the explosions was great enough that I didn’t want any condensers too close, so I stuck with 3 dynamics for the close mics. I had a D112 to see what kind of thump I could get, an SM57 (because hey, why not…), and an MD421. The 57 was about 5 feet from the launch point, the 421 was about 8 feet, and the D112 at 15 feet.

For the mid range machine, I used 4 condensors. I set up a sort of “array” of mics – I had 2 MKH60s set up at 90 degrees with a CS-3e in between them to pick up a strong center, or just to use as a mono if I wanted (I like options!). All of that was centered on the launch point. Then I had an MKH416 set up directly behind them, pointed up (45ish degrees from parallel to the ground) to pick up the mortar explosions. All of this was set up about 75 – 100 feet from the launch point.

The distant rig was about 1000 feet away and consisted of a Sanken CSS-5 in Normal mode and a Neumann KMR81i (the Neumann was actually pointed into the woods to pick up even more reflections).

Next was the actual setup and recording of the fireworks. We arrived on location around noon, and we had a lot of work to do, so we had to work fairly quickly. We decided on a launch point and set up the mics accordingly. We set up the close and medium recorders in the back of the SUV, and set up the far recorder by the other car, about 1000 feet away.

We had a table to set up all of our ordinance, so we unloaded all of that and organized it. We did a few test shots to figure out where the reflections were coming from and to get levels. We made a few adjustments, then prepped to start. Quick note about the far recorder – I didn’t have a remote record system with me, and I didn’t feel like walking a quarter mile every time I wanted start and stop the recorder, so I just set it to auto-advance the take every time the file size hit 1.5GB. We did a few more test shots while monitoring this recorder, then just hit record and left it, crossing our fingers! Since the trip, I’ve built a remote start / TC sync system (by sending TC over a wireless system) so I don’t have to do that again. Another cool tid bit – the far 744T ran for 7 hours without us touching it! We used an IDX NP1 LI battery on it.

The first items we recorded were these “little” firecrackers that didn’t have any English written on them. Apparently, in the fireworks community, they are referred to as “Happies”. They are basically the equivalent punch of an M80- but they are a little more densely packed, so they are slightly smaller, but deliver nearly the same bang. Let me tell you, they are a but scary for something that small. Not something you really want to be that close to when they go off! Luckily, we only set the ground on fire a handful of times with these. :-) (Another side note – bring a fire extinguisher!)

It’s a bit difficult to monitor these types of levels – the transients are so loud, but very quick – it makes you want to turn your levels down a lot lower than you need to, but then you don’t get the tails as well. The trick it to engage the limiters, then find the middle ground. For me, it required a few minutes of tweaking and about 5 – 8 test shots to get it where I liked it. Also, it’s not good enough to just monitor during the recording. In fact, it’s nearly useless to monitor while recording (not that I’m advocating that you shouldn’t – I do) because the sound from the source is so loud that you can’t really differentiate between the source sound and the monitored sound. I might suggest you getting a pair of those HN-7506 headphones to help, and possibly have a barrier between you and the sound if you really want to be able to monitor while recording. It is very important, however, to listen back after the recordings to hear what you actually got.

A little later in the day we started shooting off the mortars. These were big mortars. They were 2″ shells and were a bit heavy. The tube supplied with them was MUCH thicker than any other mortar launching tube I’ve seen. They slightly frightened me too. We set everything up (keeping the basic setup from before, just adjusting the close mics to the new height of the tube instead of firing from the ground.

We used the same basic techniques as described for the first explosives, and just adjusted for the new levels. Here is a sample of a few of the final mixed sounds: (turn it up!!!)

These are a few of the launches out of the tube:

Here’s one of the explosions:

So, all in all, I consider it a successful session. We got a lot of great sounds with minimal noise from birds, insects and wind. A lot of these sounds ended up as source for my soon-to-be-released LFE library, and I’ll be releasing an Explosions library later this Summer. Fun stuff!

Next up: Guns!


  1. Great article, Colin, I quite enjoyed reading it.

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