[ Hypnos Forum ]

MUSIC, AMBIENCE AND SOUND ART => Music Gearheads Tech Talk => Topic started by: triksterb on April 26, 2010, 06:47:19 PM

Title: Questions about field recording
Post by: triksterb on April 26, 2010, 06:47:19 PM
I suppose these questions are about field recording techniques using hand held recorders.

I've got a Tascam DR 1 which I've had for about 3 years that I've never really used due to not really needing it.  Lately I've began trying to use it again and I remember why I never played with it much.  I tried to record a thunderstorm recently, and while the rain was at an acceptable quality, the thunder, well, you can hear a small sample here from an hour long recording:  http://www.sendspace.com/file/dsthef (just click download) 

I don't get why it sounds terrible like that when the rain was fine; it completely drowns out the rain and pans back and forth in a unpleasing way.  The thing is that the gain is ridiculously low; looking at a waveform of it shows that it is extremely quiet and is far (far) from clipping, yet it sounds like the thunder is just overloading it and the DR 1 is freaking out about it.  I'm pretty sure it's not wind because then it would happen all over the recording; it only happens when the thunder hits.  I messed with settings like a low cut filter on the DR 1 for different recordings and it still persisted.

If I record something, I'll usually just set it on a chair and leave it for a bit.  It seems to happen with anything I record with it; I'll have a recording of something quiet, and then as soon as something slightly louder comes in, it just covers up everything and sounds terrible.  Maybe I'm wrong and this is how it's actually supposed to be.

Every recording of a thunderstorm I've heard sounded really good; you could hear the thunder against the rain.  Any field recording I've heard have sounded pretty good as well.  So I guess my question is how do you do field recordings with small hand held recorders that have mics built in?  I just use the Tascam DR 1's built in mics, and I'm sure that they are actually not great and that is my problem.  Am I expecting too much out of this thing and all hand held recorders?
Title: Re: Questions about field recording
Post by: MarkM on April 26, 2010, 07:04:48 PM
I am no expert, but it sounds like you have automatic gain control activated. I would go manual.
Title: Re: Questions about field recording
Post by: APK on April 26, 2010, 07:07:52 PM
That does sound pretty bad ... and yet the rain is fine. Very odd.
Its as though a limiter is kicking in when the attack of the thunder hits and its acting more like a gate. Does the DR 1 have any form of limiter on it that might be doing this? one that you can adjust or turn off?
Title: Re: Questions about field recording
Post by: APK on April 26, 2010, 07:09:38 PM
Yes, as Mark just said ... an automatic gain control would probably cut volume like this.

I just checked the web for the DR 1 and indeed, there is a peak limiter on the beast.
So when you start recording the relatively quiet rain it adjusts itself to that volume, but then the thunder suddenly hits and and it tries to maintain the earlier volume level by drastically cutting the thunder onset ...  which it doesn't do very well.
Title: Re: Questions about field recording
Post by: triksterb on April 26, 2010, 10:24:16 PM
Hmm... I think the limiter control might be it, actually.  It was set to Auto, so I'm guessing that means it automatically maintains the rain volume and then does like APK said. (and it has a setting called LMT which stands for Limit obviously, but no idea how it's different from Auto)  I've set it to OFF and hopefully that was it.  Thanks for pointing that out guys!

Another thought I had is about the gain control.  On the side of the unit is the input volume which goes from 0-10.  And in the menu, there is a setting called Gain with LOW, MID, and HIGH.  I think I was using the input at 10 and the gain set to LOW, and the resulting audio file is always super quiet and barely even shows up in a waveform editor; do you guys think it would be a better idea to set it to MID or even HIGH (could HIGH possibly introduce distortion?) and set the input volume to what's needed?  It's probably a better idea to keep the input volume around 6-8 since I keep thinking that even though the audio is quiet, the input volume at 10 can cause distortion, but I have no idea if there's any truth to that.  I'm also super paranoid about any clipping that may occur if it's set too high...

Thanks for all the help guys!
Title: Re: Questions about field recording
Post by: APK on April 27, 2010, 05:35:53 AM
Sounds like the Low Mid High settings are the amount of amplification (gain) the unit allows. So if you are recording relatively high volume sources you may only need it on Low or Mid, that way the 1-10 setting will not boost the signal too much. But those Low Mid High settings are probably also designed for when you use external mics that may be more sensitive or weaker than the built-in ones.

The LMT setting is probably a basic limiter, which is designed to stop clipping. So may be useful. It will only affect the loudest signals. The AUTO setting probably raises up the lower signals as well as lower the higher.

Generally you should set the Low Mid High setting to suit your general needs, and maybe the manual will tell you which one best suites the mics on the unit. You would then rarely need to change it. You should use the 1-10 knob to then set the record level to suit your source sounds. The usual rule is that you set it while listening to the loudest the source is going to get, making sure its meter does not hit the end. And yes, best not to put it up at 10 unless necessary. If you get distortion in your recordings, then you are recording too high. Easy enough to practice on a washing machine or tv channel to make sure its behaving and giving you a good recording of the material.

Hope that helps.

Title: Re: Questions about field recording
Post by: triksterb on April 28, 2010, 08:11:08 PM
Some good advice, thanks.

I did 2 tests yesterday.  The DR 1 was placed in front of a TV and I raised the volume equally for both tests.  One test had the Limiter set to OFF and the other had it set to AUTO.  These were the results:

http://www.sendspace.com/file/k88bqc Limit OFF

http://www.sendspace.com/file/zjlqwh  Limit AUTO

I think it's pretty obvious that the limiter was my problem after all; it's only present for a few seconds at the end, but it's definitely there in the AUTO sample while the OFF sample is clear throughout the entire thing.  They both have similar levels and the DR 1 did not move an inch.

In conclusion, I'm going to proceed to never use the limiter on the DR 1 ever since it caused me to not use the DR 1 for 3 years, and besides, it's probably better to apply necessary limiting in the production stage.  Thanks APK and Mark for all of your help!
Title: Re: Questions about field recording
Post by: rich on June 19, 2010, 07:41:54 PM
although, i have not listened to the sample recording...deffinitely check to ensure auto gain control is turned off. use the peak limiter as well. one thing i dont believe was mentioned, a windscreen. are you using a windscreen?