Surround Compressor

The Surround Compressor, based on the Compressor, is specifically designed for compression of complete surround mixes. It is commonly inserted in a surround output channel strip, or in audio or aux channel strips—busses—that carry multichannel audio.

You can adjust the compression ratio, knee, attack, and release for the main, side, surround, and LFE channels, depending on the chosen surround format. All channels include an integrated limiter and provide independent threshold and output level controls.

You can link channels by assigning them to one of three groups. When you adjust the threshold or output parameter of any grouped channel, the parameter adjustment is mirrored by all channels assigned to the group.

The Surround Compressor is divided into three sections:

• The Link section at the top contains a series of menus where you assign each channel to a group. See Surround Compressor Link Parameters.

• The Main section includes controls common to all the main channels, and the threshold and output controls for each channel. See Surround Compressor Main Parameters.

• The LFE section on the lower right includes separate controls for the LFE channel. See Surround Compressor LFE Parameters.

Surround Compressor Link Parameters

The Surround Compressor’s Link section provides the following parameters:

• Circuit Type pop-up menu: Choose the type of circuit emulated by the Compressor. The choices are Platinum, Classic A_R, Classic A_U, VCA, FET, and Opto (optical).
• Grp. (Group) pop-up menus: Set group membership for each channel (A, B, C, or no group (indicated by -). Moving the Threshold or Output Level slider for any grouped channel will move the sliders for all channels assigned to that group.

  Tip: Press Command and Option while moving the Threshold or Output Level slider of a grouped channel to temporarily unlink the channel from the group. This allows you to make independent threshold settings while maintaining the side-chain detection link necessary for a stable surround image.

• Byp (Bypass) buttons: Independently bypasses the corresponding channel unless grouped. If the channel belongs to a group, all channels in the group are bypassed.
• Detection pop-up menu: Determines if the Surround Compressor uses the maximum level of each signal (Max) or the summed level of all signals (Sum) to exceed or fall below the threshold.

  • If Max is chosen, and any of the surround channels exceeds or falls below the Threshold, that channel (or grouped channels) is compressed.

  • If Sum is chosen, the combined level of all channels must exceed the Threshold before compression occurs.

Surround Compressor Main Parameters

The Surround Compressor’s Main section provides the following parameters:

• Ratio knob and field: Sets the ratio of signal reduction when the threshold is exceeded.
• Knee knob and field: Determines the ratio of compression at levels close to the threshold.
• Attack knob and field: Sets the amount of time it takes to reach full compression, after the signal exceeds the threshold.
• Release knob and field: Sets the amount of time it takes to return to 0 compression, after the signal falls below the threshold.
• Auto button: When the Auto button is enabled, the release time dynamically adjusts to the audio material.
• Limiter button: Turns limiting for the main channels on or off.
• Threshold knob and field: Sets the threshold for the limiter on the main channels.
• Main Compressor Threshold sliders and fields: Set the threshold level for each channel—including the LFE channel, which also has independent controls.
• Main Output Levels sliders and fields: Set the output level for each channel—including the LFE channel, which has independent controls.

Surround Compressor LFE Parameters

The Surround Compressor’s LFE section provides the following parameters:

• Ratio knob and field: Sets the compression ratio for the LFE channel.
• Knee knob and field: Sets the knee for the LFE channel.
• Attack knob and field: Sets the attack time for the LFE channel.
• Release knob and field: Sets the release time for the LFE channel.
• Auto button: When the Auto button is enabled, the release time automatically adjusts to the audio signal.
• Threshold knob and field: Sets the threshold for the limiter on the LFE channel.
• Limiter button: Enables and disables limiting for the LFE channel.