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Yesterday I had the good fortune to do some car drop recordings. Needless to say it was loud and great fun ;) There was 4 other recordists there and during the after session beers we were discussing different techniques for recording loud transient sounds. Some like to record with really high gain, bouncing the transients off the limiter, others like to record clean without clipping the transient. Both have valid reasons why they record the way they do - so I open the question to you guys, How do you like to record loud transients and why?

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IMO loud sounds require many channels of audio. Its very difficult to get a good recording of a loud sound with just two tracks because of how many parts a loud sound can be broken into (each requiring a different gain setting and mic perspective)

I typically try to evaluate and cover the following parts:

  • low end - how much low end is the sound generating and what's the best angle to record that from? I'll typically try to have a "punch" mic that has the sole purpose of capturing the low end of the thing. gain set non clipping, no highpass in the chain, good mic for gathering low end, etc.

  • midrange transient - dynamics or warm mics are good for this part of the sound. sometimes I'll run two channels aimed at capturing this part of the sound set to different gain stages. If I highpass I do it before the limiter in the mixer. limiters can mess up the low end when they engage.

  • reverberation - I'll typically spend 4 to 6 channels focused exclusively on reverb. Loud sounds are defined by the characteristics of the space that they're recorded in, and recording the reverb as a direct source is key in capturing that space and defining the sound. Reverb mics tend to be relatively far away, and aimed not at the source but at the reflecting surfaces. Quiet smooth mics work well for this, with gain settings run up pretty high. limiters off and let sound clip if it needs to clip - these mics are for everything else. Spaced omnis and PZMs can be the secret sauce here. In the final mix, it can be amazing how much your rely on these mics at hot levels to really define the sound.

  • capsule foldback - its good to have a nice aggressively recorded channel to add some meanness to the sound. typically i'll find a mic whose capsule can't really handle the spl that the loud thing is emitting and will put that relatively close to the source so that the spl can fold the capsule back. lav mics work well for this, and the 416 sounds good when its folding back as well. Cheap camera mics and electronics can achieve this too.

  • experiments - loud sounds require lots of access and prep time, so why not set some stuff up you haven't tried yet and won't rely on working out? things like contact mics on nearby stuff, mics in and on things that might resonate in a cool way, mics you haven't tried in this application yet, etc.

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Great answer - thanks - Out of curiosity do you take the height of your mics from the ground into account when trying to get the mid and low range. Also contacts mics are great. did a gun session a few months back where there was a metal gun cabinet to the side of the range. Stuck a contact mic on that which gave us the most brilliant metal resonance. –  RedSonic01 Sep 4 '12 at 6:57
    
I honestly don't consider height, though I suppose I should. a few weeks ago I recorded a jet taking off with some contact mics I had attached to a nearby vehicle. neat! –  Rene Sep 4 '12 at 11:24
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I always have the limiters engaged on my recorders, no matter what I'm recording. But, it is absolutely essential with the loud stuff (guns, explos, jet bikes, car drops, etc). The hardest thing about recording a loud source is that you can't monitor while you record. Well, you can monitor, but you won't hear it well enough to get a feel for the recordings. Playback after takes is essential, so that you know what adjustments to make.

I find that if your recordings are distorting, the first thing to change is your mic placement. Move the mic further away or point it away from the source. Likewise, if you are not getting enough level, move your stuff closer. Also realize that some mics just won't like a particular source, so don't be afraid to swap mics out. Of course, you still need to understand proper gain settings, your mic pres should not be jacked up all the way, nor should they be turned down to near zero. Mic pads are also a good thing to have around.

Also, I tend to record loud stuff pretty hot, especially the transient stuff.

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I'm with you on recording hot and having the limiters always on - I have found that how hot to record depends a lot on the recorder. We have a DR680 at work that hates running hot but the FR2's and 744's love it. –  RedSonic01 Sep 4 '12 at 17:18
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Rene layed this out fantastically, and I've never thought of purposefully distorting a cheap mic before—brilliant!

The equivalent technique I've always used is to record 1 or 2 additional channels with the mic medium-close to the source: far enough to capture the entire source evenly but close enough that the reverb or space doesn't take over. In post, run those channels through a compressor/limiter with aggressive settings (very fast attack, fast release). IMO, it's particularly fantastic with a nice analog compressor like an 1176, but you can use any plugin compressor too (PSP's vintagewarmer works nicely). Plugin compressors have the advantage that they often have extremely-fast attack times. The result is an alternative kind of distortion that you can run soft or loud in the mix to add harmonics and body to a loud sound. I learned this technique during school when we recorded/mixed drums.

I agree also that getting a reverb recording is CRUCIAL. Adding reverb in post might work, but keep in mind that reverb processors only process what you send them, and what you would be sending them is a close-up recording that might not fully capture the power of the source sound. It's ALWAYS better to set up additional channels to record the actual interaction with the recording space, even if you are recording in the open outdoors.

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Yes reverb is crucial especially for explosions and guns. the reverb tail from guns is something that is near impossible to recreate in post. –  RedSonic01 Sep 4 '12 at 6:59
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Whoops! I think that there might be a little fundamental misunderstanding in my personal recording theory!

I am about this RedSonic01's sentence:

Some like to record with really high gain, bouncing the transients off the limiter.

I always thought, that the only purpose of gain in portable recorders was the ability to change the monitor level for the comfortable listening. I mean, I thought that if you took two the same recorders and record the same sound (not such a loud sound that will cause the clipping) but with different gain level and later in DAW normalize those two recordings, you would receive identical sounds. Is this right? Or there is something more about microphone gain?

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@Conant In theory I think you are almost right -if you digitize exactly the same signal (same mic,same preamp etc.) then normalize one signal, the only difference should be the quantization errors caused by the normalizing and an increase in background noise. The more you normalize the more the signals differ. however if there is anything different before the DAC (in the analogue world) then your signal will be different. –  RedSonic01 Sep 6 '12 at 17:57
    
@Conant - 'perfect' recordings peak very close to 0 dbfs. the reason being that this gets the best signal to noise ratio. –  RedSonic01 Sep 6 '12 at 18:10
    
@RedSonic01 Tank you RedSonic01. But I also thought, that the less gain you have, the less noise you receive. So, in my test, when I compared recordings with different gain, I also receive (after normalization) a similar noise level. But again, this is all about portable recording. In a studio, when you can have various intermediate equipment, the mic gain of course has different purposes. –  Conant Sep 6 '12 at 18:18
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