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dB-L is a mastering plugin designed to control or boost the overall loudness of your mix and to prepare your audio for final burning onto CD. Increasing loudness of a mix dB-L uses an intelligent lookahead limiter to transparently boost the loudness of your mix. Ever tried using a normal compressor plugin to boost volume? If so, you know that a compressor with zero attack time distorts the audio, particularly with bass-heavy music. The dB-L lookahead algorithm does not suffer from this problem - even very bassy material can be boosted without problems. Controlling the mix volume - brickwall limiting dB-L can also be used as a straightforward brickwall limiter. A common problem with PC sequencers & editors is how to keep the final volume of your wav file under control. Add too much EQ or reverb - your the mix goes over the magic 0dB level, and you get digital clipping. Reduce the volume of the original to give you some headroom to work with, and you end up with a wimpy sounding mix. The solution: stick dB-L at the end of your effect chain. You can blast any level into it, and it will brickwall anything above your chosen output level. And because it uses that intelligent lookahead algorithm, you get no distortion. Dithering Dithering is the process of adding a small amount of noise to the mix, to compensate for the shortcomings of 16 bit audio. (ADDING noise? Surely not!) 16 bit audio does not perform very well at low volumes. The dynamic range of 16 bit audio only extends down to -96dB. Now that's pretty quiet, and you might think that nothing at that level would affect your mix. But in reality, a lot of the ambience in music is contained below -72dB. Now here's the problem. Most PC audio applications work at 32 bit internal resolution. Great - that's enough to faithfully store a 24 bit audio signal, with 6dB of headroom spare. But what happens when you create your 16 bit wav file to record onto CD? Well, better applications will dither. But some simply truncate your 32 bit audio by chopping off 16 bits. This results in a nasty non-linear distortion in the quiet passages of your music. Here is a simple test to hear the effect of truncation for yourself. (Please note - this test requires you to crank up your headphone volume VERY loud - don't do this through your speakers or monitors, and please be careful!). First, create a 1khz sine wave at a volume of -70dB in your wav editor. Then crank up your headphone volume and listen to the sine wave. Without dithering, the sine wave has a very harsh, almost squarewave quality to it. Now switch on dB-L dithering to "type2" (noise-shaped dithering) and listen again. You will hear a slight increase in background noise, but the sine wave now sounds like a sine wave again! Try the same test listening to the tail of a long reverb. Without dithering, you will hear an unpleasant distortion at the very end of the reverb. With dithering, the reverb will sound clean, at the expense of a very slight increase in background noise. Even if you record mainly loud rock or dance mixes, I still recommend you use dithering on your CD masters - your fades will sound so much better. If you're interested in learning more, an excellent in-depth article on the subject of dithering by Bob Katz is available on the Digital Domain Website. I also recommend you check out the article on the use of compression in mastering by the same author. It contains a lot of useful information about when (and when not) to use limiting & compression. Lookahead algorithm and latency The dB-L lookahead algorithm introduces a small amount of latency into the signal path - the audio is delayed by 3ms (if attack=hard) or 20ms (if attack=soft). This has a couple of implications:
general controls
display The VU meters on the left of the display show the exact input and output levels. (For mono signals, only the left VU meters will work). Each meter has a peak hold indicator. You can change the peak hold time from the popup menu (press right mouse button) The blue meter on the right shows the amount of limiting currently being applied. For transparent results, this meter should normally read no more than 6dB, or occasional peaks of 9dB. Much more than this and you will start to hear a "pumping" effect in the audio. gain Increases the volume of the audio. (For those interested, this control actually decreases the limiter threshold, while simultaneously increasing the plugin output gain). The amount of boost you can sensibly apply depends on the material. A raw mix might be able to take 12dB of boost. However, a mix which has already been compressed might only have 3dB of potential boost left in it. Remember that over-boosting any material can be a bad thing - you could end up with a very loud but very dull mix, free of any dynamic interest whatsoever. release Sets the release time of the limiter - the time taken for the limiter to return to normal gain. In general, you should set this control as low as you can without introducing any distortion into the output. For most materials, if you are boosting less than 6dB, a release time of around 20-50ms usually works well. As you increase the boost setting, you will need to increase the release setting too. output Sets the maximum output level. attack dB-L offers two different lookahead algorithms. In normal use, you should leave this button set to hard, which will work well for the majority of mixes. However, you may occasionally have extremely bass-heavy audio which you want to process using dB-L - for example a raw synth pad. For these, the soft setting (which uses a longer lookahead time of 20ms and a different attack algorithm) can provide better results. dither
type1
dithering adds a precise amount of white noise to the audio. This is
pure dithering, and is guaranteed to mask all 16 bit truncation
distortion (see the introduction on dithering for an explanation) Very Important - when you use dithering, dB-L must be the very last effect in the chain, and the last effect you apply to your audio before burning to CD. Never apply any further processing to a wave file which has already been dithered. ALWAYS DITHER LAST! bypass Switches off the plugin. Pretty dull control really. But useful for doing A/B comparisons between the original & processed audio, particularly when your sequencer or editor doesn't have its own effect bypass button.
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dB-L
mastering limiter