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Limiting

Discussion in 'Mastering' started by nathan_b, Sep 4, 2012.

  1. nathan_b

    nathan_b New Member

    I've been using Logic Pro 9 for a while now and I am learning things as I go. So far I have made several awesome sounding acoustic/post-acoustic using the software. In a new one that I am currently trying to master and put on my iTunes, I can't seem to get the Limiting down correctly. So far I've completed songs using the Ad. Limiter to cut down the overbearing signals on the final output, without any noticeable sound reduction, clipping, or major distortion. But on this newer one, I've been trying the same techniques used before and I can't seem to get it to sound right on my iTunes. I have the Ad. Limiter set with an input scale of -3db, a gain of 2db, and an out ceiling of -1db. It sounds fine when played through Logic, but when bounced onto my iTunes there is mad distortion on the parts where it seems the limiter I set should be working. If anyone has any experience with how to correctly use Limiters please help me out, right now I'm not sure what I'm doing, all I know is that the songs I produce sound good. Thanks
     
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  3. Antiphones

    Antiphones Member

    an output ceiling of -1 will protect you against any actual clipping from overshooting on the output faders. I'm assuming the limiter was the last thing in the chain on the output faders? If so the output faders should have peaked at -1. Try opening the bounced file and see if it ever hits 0 db, the highest point should be -1.

    If none of these things show up the problem then I can only guess that the limiter is causing distortion but that it only becomes apparent when its compressed as mp3/AAC. How good are your monitors? If they're not great, you may not hear distortion in the mix which is there, and that may be made more apparent by mp3/AAC compression.

    How hard are you driving the limiter? If it is being driven hard, it will distort that's just a fact of life. The better the limiter the less unpleasant and less noticeable the distortion when you drive it hard. I don't use Logic's limiter, but I occasionally get logic files sent to me where someone has it on so I know the sound and I don't consider it to be a very clean limiter.

    Try a different limiter. Download a demo of PSP Xenon for example, its arguably the most transparent software limiter on the market. See if that solves the problem and if its does, it might be worth the investment.
     
  4. nathan_b

    nathan_b New Member

    I don't use monitors i usually do all my listening through either some pretty good headphones (Panasonic rp htx7), or some average ones (sony mdr-v150). Also what does it mean to 'drive the limiter'?

    another thing that i'm curious about, is that separately, each track that i've recorded does not clip. in fact the sound waves are quite far from reaching 0db. When played all together, the stereo output maxes out at 6db without a limiter. I've compressed several of my most powerful tracks to make sure their signal doesn't max out, and when listening through logic, the song sounds fine (without limiter, and the output still maxes at 6db). But when trying to limit the whole output is when the mad distortion comes in.
     
  5. Antiphones

    Antiphones Member

    Try bouncing without the limiter and see if you get the distortion when its converted to AAC. If you don't then you know its the limiter which is causing the distortion, or at least you know its emphasising it.

    Limiters stop the signal from exceeding the out ceiling. This may sound simple but its actually a very complex process if you want the result to sound good. As you raise the input of the signal into the limiter more and more of the signal hits the ceiling. This allows you to raise the volume of the track without exceeding 0dB. However, as more and more of the audio gets levelled at the ceiling, the sound will change and it will distort. Its impossible for it not to distort in one way or anther. Imagine you had a mountain range made out of paper and you started to press a board down on it flattening the peaks. You would distort the shape of the mountains. Audio is analogous. The higher you raise the input level into the limiter, the more of the music gets "squashed" when it hits the ceiling, and the more distortion you get. The better the limiter, the nicer the distortion sounds, but there will be distortion if you push up against the ceiling. A great limiter makes it sound like there isn't any distortion, even though there is. Unless you push the signal so hard against the ceiling that no limiter can possibly stop it sounding distorted. Some people like this distorted effect for some kinds of music. Its called driving the limiter.

    If you want to minimise the distortion, then you need to just be limiting the loud momentary transients in the music, which means the signal should only hit the ceiling now and again and not for very long. The music may not sound as loud as if you drive the limiter, but you'll get less distortion. Its a matter of taste and market expectations for the style of music.

    Hope this helps
     
  6. nathan_b

    nathan_b New Member

    well thanks very much for all the info. I've got a lot of new stuff to try out and learn so I really appreciate your help!
     
  7. Antiphones

    Antiphones Member

    No problem. :)
     
  8. joelonsdale

    joelonsdale New Member

    You may find that the clipping is due to frequencies the aiff/mp3 conversion process cannot deal with effectively or maybe the cheap converters in your (and everyones!) iPod cannot deal with! Try the following chain on your master output: 1-highcut at 19khz, 2-lowcut at 28hz, 3-compressor on platinum with only 2 db of reduction showing and no make-up-gain, 4-adlimiter knocking of 2db with output set at 0db, 5-standard limiter knocking off another 2db with output set to -0.1db. You may need to tweak these settings a little...

    It could also be due to the master output being fed to much signal - turning down the master output or attenuating it with a gainer set to a minus figure is NOT the same as reducing the volume of all it's contributory tracks. Make sure all the volumes are nice and low (compensate by turning your monitors up!) and if you see NO RED LIGHTS then you are doing well! You can bring the volume back up with plug-ins on the master output, perhaps the gainer or just the make-up gain on the compressor. Also, make sure the volume of the Apple o/s itself is on unity gain - if this has got turned up you may not notice, but the distortions may create havoc behind the scenes.
     
  9. Leon Gilroy

    Leon Gilroy New Member

    i had a scan but not sure if anybody mentioned this...make sure your individual tracks aren't all hogging the same frequencies, essentially try (if you havent) cleaning up the mix, your style may call for it but i try not to have any overbearing frequencies hit the output...if im not wrong and its the case then try being really strict with frequency space to root out the problem.

    the mountain metaphor was a good one so im gonna steal it...try not to have too many mountains in the same place.

    Im no expert at all but if i ever use a limiter to 'squash' the output its by a very small amount as a last resort, usually i use it to make sure the outputs loud enough for listening.
     

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