Alloy’s Limiter serves two purposes: it allows you to aggressively limit high level signals to prevent clipping, and it allows you to create an overall louder or fuller sound by limiting the dynamic range and boosting the perceived overall level of the audio.
Key Features:
• Soft and Brickwall limiting algorithms
• Release control helps you fine tune the Limiter’s response perfectly to your source material
• Gain Reduction and Histogram meters provide valuable visual feedback
Threshold: Determines the level at which the limiter will begin limiting. Turning down the threshold limits more of the signal which in turn will create an overall louder output. In other words, by turning down the Threshold you limit the dynamic range of the audio. The limiter also automatically applies gain as you bring down the Threshold, boosting the overall level of your audio.
Release: This is the release time in milliseconds for the particular limiting algorithm being used. In general, more extreme limiting will benefit from longer release times.
Margin: Determines how much to boost the output signal after limiting. If the Margin is set to 0 dB, the signal will be boosted all the way up to 0 dB. If the Margin is set to -0.3 dB, makeup gain will be applied until the output signal is at -0.3 dB. Note that in the Soft mode, the level may be allowed to cross the Margin setting, while in Brickwall mode the Margin serves as an absolute "stop" point.
Mode: This allows you to select between the two types of limiting algorithms (Soft and Brickwall).
Soft: The soft limiting algorithm uses the Margin output value as a guide but not as a fixed limit for the output level. It provides a natural "soft" limiting effect at the expense of allowing the level to exceed the Margin.
Brickwall: The brickwall limiter, on the other hand, uses the Margin output value as an absolute guide, and the final output level will not exceed this point.
Both algorithms provide a natural analog limiter effect, so the choice is related more to the behavior of the limiter and the output level than a choice in sound quality.
Limiter Meters
A loudness histogram level meter gives you visual feedback to help you set the Limiter. The height of the level meter represents the level at any point in time of the mix, while the width shows the history of the level over time. As you decrease the Threshold, the top of the meter will become red. This indicates the range that is being limited.
By default, the range of the meter is from 0 dB to -64 dB. You can adjust the range by pressing down the Ctrl key under Windows or the Command key under OS X and clicking with the left mouse button to zoom in or clicking with the right mouse button to zoom out. Under OS X you can also Command-ctrl-click to zoom out.
Alloy also provides a gain reduction meter next to the threshold slider, which provides a visual and numeric decibel readout of the amount of limiting or gain reduction that is being applied.
Phase Tools
Rotate Phase:
By rotating the phase, this feature can help reduce asymmetric waveforms that are found in dialog and voice. Making the waveform more symmetrical allows the voice to ride perceivably higher in the mix. This is useful in broadcast radio and dialog mixing.
This effect can be viewed in the Phase Tools meter just above Rotate Phase. The waveform is displayed in real-time in yellow. When Rotate Phase, Invert Phase, or Filter DC Offset is enabled, the effected waveform will be shown in shaded grey underneath the yellow waveform.
Amount: This parameter controls the amount of phase rotation of your signal will be rotated in order to account for any asymmetrical waveforms.
Invert Phase: When activated, this will flip the phase of the (L)eft, (R)ight, or both channels from positive to negative and from negative to positive.
Filter DC Offset
DC offset is characterized by an audio signal’s average waveform being offset slightly from zero. This in most cases is undesirable as this offset will rob your final output signal of extra headroom, keeping your audio from reaching the maximum possible output volume.
The advantage of performing the DC correction with Alloy is that it's after all of Alloy’s internal effects and filters drifting DC offset in real-time as opposed to just applying an average offset correction for the mix.