Zoom H4n/Sound devices mixpre while recording sharp loud sounds

[askomiko]

Hi!

How does the Zoom H4n's limiter work with loud, sharp sounds, like a snare drum or gunshot? Is there any chance to get a good sound from a shooting range?

Other piece of gear that sparked my interest was the Sound Devices mixpre, since it supposedly has a good limiter hidden inside. Has anyone recorded gunshots with that?

So far I've gotten surprisingly good results from just a cheap camcorder, where the auto gain control works sufficiently good to keep the sound from distorting. Then again, the AGC sucks otherwise, eg. the quiet ambience after the shot is bad again... And if the camera is set to manual level, there is nothing keeping the peaks from distorting. So, I'm in need of a working compromise here. (Using foley is not an option, this video is going to a gun sound suppressor manufacturer..)

 

[dre83]

gunshot has a very fast attack about 120dB SPL I think... at after a slow "run out".

Something like PANngggggggggggggggg. So you could use the compressor of the H4N, but I don't think that would be enought.... Lowering the levels... fort the PAN it's ok.. for the nggggggg it will be to low...

Gunshots are often recorded on analogue tapes, because of there "fysical headroom".

But a good compressor/limiter between the H4N and the mice-preamp could work.

 

[Alex H.]

Recording with compression isn't the best idea. The more processing you add when you record, the less chance you have to correct it in post (once it's recorded, you're committed). If you are doing FX recording, and you know that you'll be working with isolated sounds like the aforementioned gunshot, your best bet is to lower the input gain on the MixPre. Do a couple of tests to make sure that the sound isn't overmodulating and still has no less than 6dB of headroom, and then record away.

If these are loud sounds that are occurring within other scenes and dialog, well... the limiter on the MixPre is going to be your safety net. If the sounds peak in the MixPre and overmodulate there, it really doesn't matter what limiting/compression the H4N has going on. Again, do sound checks beforehand and make sure that your limiter's threshold is catching those sudden peaks.

 

[unclebob6958]

If you are using the internal mics on the H4n they are not designed to capture high SPL sound sources. Your best bet is to disengage the limiter and turn the input levels way down.

If you are going to add the MixPre to your arsenal you may want to use a dynamic mic to record the shot and a condenser to record the tail. Record them as two separate tracks, then you can mix to taste in audio post. Your mic positioning is also going to be crucial, so a little experimentation will be required.

Sounds with loud, short, sharp attacks that also have long "tails" are among the hardest sounds to record. Charles Maynes, one of the weapons recording experts with numerous films and video games to his credit, has written quite a bit about recording gunshots, tanks, cannons, etc. in various forums so you may want to try a Google search. Try the Yahoo! sound_design group.

 

[askomiko]

Thanks for the suggestions, and specially mentioning Mr. Maynes. I found this very good thread: http://www.gearslutz.com/board/post-production-forum/95756-how-recording-gunshots-2.html

Recording with compression isn't the best idea. The more processing you add when you record, the less chance you have to correct it in post (once it's recorded, you're committed).

True, but with a big rifle shot going around 150-160db, it's rather close to impossible to record it without some sort of limiting. Even most mics simply fail at those SPL levels. My plan was to start the experiments with Shure SM57s.

I have some older sound effect CD's, and the gunshot sounds in them really really suck. I guess that's what happens when you record them with very good equipment and try to preserve the waveform in its original form. If the levels are set very low, you only get a click, and pretty much nothing else. And most likely, even the click is distorted.

With the H4n's 4 tracks, I also planned to use all tracks, dynamic mics set very low level, trying to to get something of the peak, and the built in mics set at higher level for the tail. Original plan was to carry my PC to the range and record with 10 mics and tracks at once, but maybe I won't bother going that far.

Now that I think of it, the Canon camcorder is doing an amazing job here, maybe I will get the shot sounds from there and everything else from other equipment.

 

[Alex H.]

True, but with a big rifle shot going around 150-160db, it's rather close to impossible to record it without some sort of limiting.

There's a huge difference between limiting and compression. What I was suggesting was that you rely on the limiter in the MixPre, rather than using compression in the H4N.