What exactly does the look ahead function of digital limters do.

Is it a good or sometimes negative thing.


Cheers

A look ahead limiter allows for a perfect "brick wall" to be achieve in limiting. If you can look ahead in the signal, the limiter can anticipate loud peaks before they occur and lower the volume before they arrive, so that the audio never exceeds the threshold. This is also sometimes refered to as a negative attack time.

As far as I know this is the only benefit. For digital formats, it's pretty important to never exceed 0dBFS, explaining why look ahead limiters are so popular in mastering.

Maybe someone like Mr. Katz can chime in to better explain the pros and cons of this type of limiting.

It allows a zero attack time by delaying the input relative to the side chain so you can "see the peak coming."

Rarely used in anything but brick-wall limiters. Was either a breakthrough or an ear-breaker, depending on how you look at it....

DC

Thanks guys.



So if a limiter has the option to select look ahead, is it a good idea to do so?

Is there a down side?

Not being able to decide for yourself, I guess....

DC

Now That's ****in' funny.

Thanks guys.



You mongrels.



I love DC

There's actually an argument for not using look-ahead having to do with the character of the distortion that's generated.

Thats what i was chasing.


Cheers

Or anyone else who knows the answer! Here's my point of view: Look-ahead is EXTREMELY important in digital limiting where you must catch peaks even as short as a sample. Lookahead is available in compressors as well as limiters but much less important. Basically, with compression, the true attack time cannot be shorter than the lookahead. For example, if you look ahead by 10 ms, then any transients shorter than 10 ms will be caught. But if you're like me, and tend to use much longer attack times with compressors, lookahead is probably an academic argument, and your 1 or 10 or whatever millisecond lookahead is probably meaningless if you are running a much longer attack time. But if you want a true 5 ms attack time, you better have a lookahead that's 5 to 10 ms.

However, when I'm doing parallel compression with a very fast attack time, I have to use a parallel compressor with a lookahead of at least 10 ms. Otherwise the transients will be stomped on. So lookahead is very important if you are using a parallel compression technique to try to preserve transients.

Thanks a lot Bob.

On some devices or plug in's- increased latency.