Curious about limiters

[MeAgain]

I worked with the 702T over the weekend for the first time recording sound FX in the field, and for all intents and purposes, I'm an audio newbie.

I noticed the limiter was on, and figured out what it did, but didn't realize I could change the peak ceiling (or threshold). I was thinking of taking it off, but was moving pretty run and gun, so rather than overlook a bunch of peaks and ruin some takes, I kept it on. It was reaching -12db on peaks and sometimes around -6db on louder sounds, so I figured I was getting good levels.


So now, I'm just sort of curious about limiters, using the 702T as an example. As I sit here looking at my peaks, I see s lot of them hit -6db so I imagine the limiter was set to this? How much compression is there on a 702? Does it only start to compress when something REACHES a certain db level, or does a limiter simply stay on and effect the entire dynamic range through and through?

Sorry if this is a common topic- I'd like to learn about limiters now so I can use them the best way possible next time- any good article links would be appreciated.

Thanks

 

[Chadfish]

A limiter is a brick wall line that a signal can't go above. Anything that hits the threshhold will be prevented from going above that point. This is a god thing much of the time. If you have transients like a hand clap, the limiter will save the day. It's not always a bad thing that your audio is effected by limiting. Too much is going to color your sound though. A limiter is different than a compressor. A limiter just cuts off the top of the peaks (or compresses them), where a compressor will both boost the overall signal while lowering the volume of peaks by a set ammount. At it's extreme settings a compressor acts like a limiter. A compressor will bring your noise level up by boosting the signal. Not cool.

I don't know about the unit you were using, but it may have a limiting threshold above where you were hitting with your peaks. If your peaks are consistently -6db, then that's where it's set to. I would probably set my limiter at -3db.

 

[Petrus]

Not so.

If a limiter would just cut off the peaks it would be doing the same thing clipping does for free, but at lower level. Who would want that???

Limiter IS a compressor, a special kind steep compressor, which works only at the last few dB of the digital scale. I do not remember how the limiter is set on SD7xx series (I have 722), but on the SD302 mixer I have set it to +17 dBVU (-3 DbFS) and it compresses at 1:20 ratio by default above that. Basically it gives a whooping 60 dB extra safety at the top!