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look ahead analog limiting

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look ahead analog limiting

Postby MadManDan » Sun May 20, 2012 6:04 am

So I have a song in my head that I hope to get done sometime soon. Genre is metal-ish. Begins with a quiet intro and kicks in very loud.

I must state that I am against the volume wars. Yes, I plan on compressing the mix elements tastefully, but not to death. For mastering, my colleague has a boat-load of boutique limiters and I do plan on giving the overall mix a little tasteful squash. Think along lines of the last of the vynil days.

My question is this: when the loud part kicks in, I feel there might be an audible duck when the limiters first kick-in.

I've heard about look ahead limiting.
Does it work like this: put mix on stereo track A, which goes thru the limiter. Put copy on track B, slide that ahead a smidge, then feed that to the limiter's key input? I imagine that the limiter will already be doing its job a fraction of a second before the signal gets there.

Is this how its done?

MMD
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Re: look ahead analog limiting

Postby Soundseed » Sun May 20, 2012 6:24 am

If you're using an analog multitrack of the pro variety, there might well be separate sync outputs, so you can take a trigger feed from the record rather than play head. It's ahead by the time it takes for the tape to pass between the two heads, so depending on your tape speed you may have 100+ ms... However, if the difference between your loud and quiet sections is so substantial that you are going to hit your limiter hard no matter what, you will always get some form of artifact.

The simplest solution is to narrow the gap between the two sections - you will still retain the dramatic effect of going e.g. from lone guitar and vocal to full blasting band, but won't have to hit your limiter so hard.

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Re: look ahead analog limiting

Postby andy cross » Sun May 20, 2012 8:26 am

MadManDan wrote:
Does it work like this: put mix on stereo track A, which goes thru the limiter. Put copy on track B, slide that ahead a smidge, then feed that to the limiter's key input? I imagine that the limiter will already be doing its job a fraction of a second before the signal gets there.

Is this how its done?

MMD

That should work. It's certainly a handy technique for gating - you can set quite a high threshold and politely ask the gate to open in advance by using a time-slipped instance of the audio.
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Re: look ahead analog limiting

Postby SafeandSound Mastering » Sun May 20, 2012 12:54 pm

Have an experiment but if this sounds better than the best digital limiters available I would be very surprised indeed.

cheers

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Re: look ahead analog limiting

Postby Hugh Robjohns » Sun May 20, 2012 3:43 pm

MadManDan wrote:Is this how its done?

In general terms, yes.

In reality the 'lookahead delay' is of the order of a few hundred microseconds (enough to let the limiter start it's attack time before the transient arrives) and is achieved with an analogue delay line comprising a lot of inductors!

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Re: look ahead analog limiting

Postby MadManDan » Mon May 21, 2012 4:16 am

Thanks everybody. I think what got confused is what equipment is being used. Standard daw. The only analog equipment is the limiter.

We could take the signal from track A, the control from track B, and print on C.

I figure we could leave the control track right where it is, no sliding,and print the entire song. Then, slide the control track up a little and punch the one spot right when the loud part hits.

I guess I'm just wrapping my head around how to have an artistically "packed" loud song while still keeping the soft part soft. I don't want anything to duck when the bomb drops. Probably the trick is to not have too many things lingering over during the transition. Lingering instruments would be heard ducking.

Even in one of the most revered rock recordings, I can hear limiters kicking in and changing levels. "Hells Bells" by ACDC. There's the bell of course, then that first electric, and when the kick comes in it squashes the guitar down. They did nothing wrong, its the nature of the "limiting beast"
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Re: look ahead analog limiting

Postby Hugh Robjohns » Mon May 21, 2012 9:13 am

Perhaps the way forward is to process the individual loud track elements with limiters or level automation so that you won't have the overall limiting/ducking issue.

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