The L-18 Surround Limiter is the most transparent dynamics device ever created by McDSP.

The L-18 offers up to 36 dB of limiter gain, limiter knee shape and release controls. The L-18 makes use of the same patented technology found in the McDSP ML4000 multi-band and dynamics processor plug-in, but in an all-analog implementation. A color control provides a subtle high frequency correction before the digital to analog conversion, and can be completely bypassed if desired.

The L-18 Surround Limiter includes support for LCR, LCRS, Quad, 5.0, 5.1, 6.0, 6.1, 7.0, 7.1, 7.0.2, and 7.1.2 formats. A set of channel modes (multi-mono, stereo pairs, front/back groups, or all channels) allow processing of the various surround channels in different groups. LFE processing can be separately disabled if needed. There is even an option for triggering all surround channels from a side chain.
  • All analog limiting and saturation stages

  • Variable limiter knee control

  • Pre-analog stage high frequency correction

  • Sample accurate automation of analog processing

  • Additional surround support including LCR, LCRS, Quad, 5.0, 5.1, 6.0, 6.1, 7.0, 7.1, 7.0.2, and 7.1.2 formats

  • Included with APB hardware purchase
  • AAX Native
Channel Linking
Surround channels can be processed independently (multi-mono), in stereo pairs (S-P), using the maximum level of all channels (ALL), in front and back groups (F/B), or using a side chain (SC). These channel linking options are available for all supported surround formats from LCR to 7.1.2.
LFE Options
LFE processing can be optionally enabled or disabled using the LFE button. There is also an LFE Soft mode for a softer limiter curve for the LFE channel only. Note the user can still select an overall limiter knee for all surround channels regardless of LFE Soft mode selection.
More Metering
When the VU+ button is pressed, an additional VU meter bridge appears beneath the main L-18 Surround Limiter interface. Surround channels are organized into logical groups of available VU meters, and the main L-18 interface VU meter continues to show the maximum signal level of all surround channels.
The LFE limiting can have a softer limiter knee than what is used for the other surround channels.
Amount of signal level boost applied to the input during limiting.
Maximum signal level output from the limiter.
Surround channels can be limited independently (same as multi- mono), in stereo pairs (S-P), the max of all channels (ALL), in front and back groups (F/B), or side chain (SC).
Rate at which limiter action stops once signal peaks are no longer detected. May be enabled for user control, or disabled and an automatic release value is calculated.
High frequency adjustment applied pre digital to analog conversion. May be be enabled or disabled.
An important aspect of any APB plug-in is that the plug-in is primarily a controller. The APB plug-in takes the input audio signal, combines it with a control signal, and sends both along a Thunderbolt connection to an APB unit for processing. The control signal sets up the analog components to do the selected algorithm with all the parameter values, and the audio signal is converted to the analog domain. The analog version of the audio signal is processed in the analog domain, and then converted back to the digital domain.

By operating the APB hardware from an APB plug-in in this way, all user controllable parameters are recallable and can be saved as presets. Furthermore, because the control signal is married to the input audio signal, parameters can be updating during playback with sample accurate automation.
List of all APB dealers.
Frequently asked questions about the APB.