contact mics and guy wires

Everyone knows that Ben Burtt made the blaster sounds in Star Wars by striking guy wires and recording them with contact mics.

Countless others have done this as well, but I needed to test out some new gear so I figured I'd give it a go.

Gear included my recently acquired Jez Riley French contact mics and my new Sound Devices mixpre that I bought to use as a front end for my PCM D50.

The entire signal path was:  doublesided carpet tape --> JRF contact mics --> Hosa MIT-129 impedance transformer --> mixpre mic ins --> mix pre tape out --> PCM D50 line in.  These recordings are 100% unedited (including gain changes - this is the level I cut them at)

re: contact mics, Tim Prebble has an excellent post outlining the entire process, but the long and the short of my setup was that the impedance transformers were absolutely required to get all of that low end out of my rig.  This is because contact mics are high-z sources and the mixpre is a low-z preamp.  In the past I've also had good luck running straight into an H4 with other contact mics, but I suspect that's because the H4 takes hi-z inputs by design.  With that said, I've never quite recorded low end like this with contact mics to date, so I was very happy with the result.

Also, I laughed a little when I saw that the BBC went into an anechoic chamber and recorded a few very tiny insects using these exact contact mics and preamps.  It's quite the testament to what they're capable of to hear them seamlessly running from centipede feet to the huge guy wire hits I got.

Here's that BBC vid (check out the contact mics visually at 2:00 and then the recording at 3:40):





Now onto my vids. First up are the guy wires.  The single most interesting thing that I discovered was that I could resonate one wire by striking the other, probably through some connection that they were making underground.  You'll see in the vid that they're not buried right next to each other though, so it's possible that the contact mics are actually just picking up sympathetic vibrations.  It's all very cool though, and there is TONS of low end, so crank up the speakers.

Again, this audio is 100% unaltered - not even gain changes.




Next up is the metal fence that was nearby.  I did some similar stuff where I was striking the surrounding objects and getting indirect vibrations, which was pretty cool.  The distortion sound in one of the channels isn't clipping, its the effect of the sticky tape losing its grip.


And for fun, here's a 96k downloadable soundcloud vers of the guy wires.  Enjoy!

it depends: condenser or not?

One of the more important decisions you make when deciding how to record something is what type of mic to use for any given perspective.

My default position tends to be to go with a condenser and then make further decisions from there because condensers are going to (generally) give me the quickest path to a flat, true recording.

In fact, there are times when you have no choice but to use a condenser to get what you're looking for.  Specifically:

• when isolating sources in moderately noisy environments

I use this description because it generally describes the reasons for using interference tube (shotgun) mics, all of which are condensers.  Shotgun mics are essential for extracting interesting sources from noisy environments, and those only come in the condenser flavor of mic.


With that said, there are some important reasons to deviate from the condenser mic perspective:

• when recording super high dBspls

When recording incredibly loud sources many condensers will blow out more quickly because they tend to have higher output than other types of mics.  Loud sources such as weapons and explosions tend to ask for multiple mic setups regardless though, because you'll tend to want to hear that loud sound reverberating out in space.  As such, I'll often pack and record with dynamic mics aimed at the source of loud things and have some condensers out and aimed at the reverberations that those things create.

• when recording super bright subjects

Condensers mics tend to be naturally pretty bright, which is great when recording things in a way that increases their ability to cut through a dense mix.  That strength becomes a weakness when the source is exceptionally bright, however.  Things like metallic impacts and electric shocks can end up sounding a little too brittle and harsh if miked up with something too bright.  Dynamics and ribbons are often good choices for balancing out the brightness of certain harsh source materials.

• when looking for non-linear sounds

Condensers are great for getting realistic representations of the things that they are aimed at, but sound design often requires some not quite true to reality sounding perspectives, and to really go there you'll need some other tools at your disposal.  This is where things like contact mics, electrostatic mics, stethoscope mics, hydrophones and the like come into play.  I'll often roll both a condenser path and a non-linear path and blend the two in post.

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I think a great recording kit can be built with very few mics, and the majority of the weight falls on the condensers.  When recording extreme sounds or looking for non-linear though, it's important to have other tools in the toolbox.

slingshots and dishes

I have a project in the house that requires the creation of a ton of bullet impacts, and while I'd love to do what Frank Bry does and go record some targets shot up with custom subsonic ammo, I don't have the resources to get that done for this specific project.

I had to get creative for many of the surfaces, using a rockhammer and a mobile rig for many things, but for the glass impacts I found myself with a slingshot, a stack of dishes and about 45 minutes in an empty warehouse to get the sounds I needed.

Since the warehouse wasn't onsite and I knew I had limited time, I decided to roll with the venerable Sure VP-88 and a 744t as my rig.  The VP-88 isn't a great ambient mic because of its relatively high self noise, but it works great as a spot fx mic when the preamps are going to be at 12 o'clock or below, and I wanted a stereo rig that would be quick and easy to set up and tear down.  I set the pre's down to zero with no pad on the 744 to leave enough headroom for the close miked impacts I was setting up to record.

I needed the sounds to be able to pass for outdoors, so that meant I had to dry up the verb in the space as much as possible for recording.  I also needed to contain and direct the debris to keep myself safe and keep cleanup quick.  I solved this by building a little pup tent using packing blankets and laying down a cheap plastic tablecloth on the floor with a light layer of sand.   I also placed a board against the wall as a backstop, and angled it away from me so that any projectiles that hit it directly would (hopefully) direct away and into the side of the tent.

I protected the mic by placing it behind a heavy wooden box that was holding up the left part of my pup tent, and just poking it through the packing blanket.  Next I set up the plates.

 Not the best picture, but you get the idea.  I stacked several towers of glasses and dishes with the intent of getting as much peripheral debris as I could when stuff fell down.

I also ended up with a happy accident regarding ammo, since my original intent was to buy solid metal slingshot ammo for the recording.  It turned out that I didn't have time to make the purchase before I had to record, so I opted for quarter sized rocks from outside. That ended up being the superior choice though, because the rocks tended to shatter on impact, and if they didn't do that they would riccochet and make generally interesting whizzing sounds on their own.

20 minutes of recording yielded these final results and a few others: (these sounds are unprocessed except for MS decoding and some slight limiting)


In the end, I was surprised by how happy I ended up being with both the noisefloor and the debris detail I managed to get.  I didn't get the warehouse verb all of the way out, but layered with an ourdoor ambiance those sounds will play.

I also don't think the soundcloud conversion does these particular sounds justice, so feel free to download them to really hear what went on there.

Here's the aftermath: