Overview

In 2015 SPL released the IRON mastering compressor based on an original concept.

Their goal was to conceive a compressor that provided a pleasant, melodic-sounding, transparent compression, inspired by the vintage compressors of the radio era. But they wanted it to be versatile enough to adapt perfectly to the needs of modern mastering studios.

Thus, the IRON combines not only the sonic virtues of legendary vintage tube compressors with the advantages of the High Dynamic 120 V operating voltage in a single unit. It also sets a new benchmark in terms of tube compressor technology, with the innovative implementation of a parallel dual-tube circuit.

Iron is a variable-bias tube compressor, often called a “Vari-Mu” design. Unlike most standard variable-bias designs, which use the bias of a single tube for compression, Iron uses a dual circuit topology. This means, the incoming signal is split between two tubes via a specially designed Mu-Metal iron transformer, running in parallel and then recombined. One tube is a 12AX7/ECC83 and the other a 12AU7/ECC82. Each tube yields a slightly different compression curve and feel.

The Attack and Release parameters have six different settings ranging from Slow to Fast. The times are not constant, they vary according to the Rectifier circuit selected: There are six different Rectifier settings available with different diodes (Germanium, Silicon, LED, mixed).

Mastering is not the only domain where the IRON sets new standards. It can also be used to process subgroups or individual signals, like vocals, bass, guitar, strings, etc.

Features

  • Variable Bias Tube Compressor
  • Parallel Dual Tube Circuit
  • Custom Mu-Metal Iron Transformers
  • Feed-forward resistive Vactrol-Opto-Isolator
  • Six different Rectifier settings available
  • Sidechain that allows you to choose between Off, four sidechain-filter presets or an external sidechain signal
  • In Link mode, the Threshold, Tube Bias, Attack, Release, and Rectifier parameters, as well as the Sidechain EQs, are controlled with the right side (channel 2) of the unit
  • Master out features an additional, Passive Equalizer with two fixed sounds
  • Brainworx plugin only features such as TMT, M/S Processing, Mono-Maker and Stereo Width, Parallel Mix and Headroom

Audio Examples

Industry Reviews

  • Gentry Studer

    Gentry Studer

    I downloaded the plug in, I've had to shoot it out against the real thing on every project, just to see how it stacks up. You guys did an amazing job with the plug in. Everything from the color it… Read More

  • Michael Romanowski

    Michael Romanowski

    I use the hardware SPL Iron for my mastering everyday. What I love about it is the tonal and dynamic flexibility is has for every style of music. And it’s always smooth and musical. Brainworx… Read More

  • Brendan Duffey

    Brendan Duffey

    When I need a tool that gives me a plethora of gain, tone and shape controls the Iron Mastering Compressor is the first thing I turn to. The Iron Plugin has all the controls features of the… Read More

Customer Reviews

  • spl iron

    ★★★★★
    by Hflex
    this thing is so fat it's obese!
    not only is it a great mastering/buss comp, in which it excels, it makes a fabulous tool for fattening up kick/bass/sub&synth tracks and is equally gorgeous on… Read More
  • Astonishing!

    ★★★★★
    by Folia Soundstudio
    Well, what an addition top my UAD Shadow Hills + UAD Manley Vari-Mu collection! It has lots of controls (read the manual to take full control over the plugin), but it is absolutely easy to… Read More
    Plugin Alliance response
    Thanks!
  • SPL Iron is huge

    ★★★★★
    by T. W. Tobin
    After using this for mastering compression on a recent EP project, all I can say is wow. This thing sounds huge. I was choosing between UAD SSL G, TDR Kotelnikov and SPL Iron. All are excellent in… Read More
  • Must have

    ★★★★★
    by Carambo
    Well, it's now my go to bus or master compressor, it can do everything, and I like that you can fine tune the sound with the Eq settings, tape emulations,... Must have in your sonic arsenal !
  • Truly gorgeous sound and soundstage. And It's ALMOST there with the GUI.

    ★★★★☆
    by In-Stereo
    I have many high end compressor plugins so it's really hard to impress me, and IRON did without a single doubt. You can go from very subtle super glue to very audible pumping to everything else in… Read More

Specification

Supported Plugin Formats
AAX DSP, AAX Native, AU, AAX AudioSuite, VST2, VST3

Supported Operating Systems
MacOS 10.9 through 10.14
Windows 7 through 10

Mac
Intel CPU only (minimum 2 GHz recommended)

PC
Intel-compatible CPU with SSE2 instruction set (Pentium 4 compatible or higher; minimum 2 GHz recommended)

System Requirements
Display resolution: 1440 × 900px or 1280 × 960px or higher
Memory: 2 GB RAM

Downloads

With the Installation Manager, you can select, download and install just the Plugin Alliance products and formats you need for your system.

ChangeLog

IRON

SPL IRON - Changelog

Version 1.2 (Nov 06, 2019)
- General: Qualified for use with macOS 10.15 Catalina
- General: Qualified for use with Windows 10 November 2019 Update
- General: Fixed plugin validation in Logic under macOS Catalina
- General: Fixed preset name restore in Logic when reopening a session
- General: Fixed opening authorization dialog triggering automation
- General: Improved instantiation times for plugins
- General: Improved license functionality and branding for subscription
- General: Removed 32-bit support on macOS and Windows
- Fixed automation highlighting for the lower area in the mono version

Version 1.1 (Jul 10, 2019)
- General: macOS 10.14.5 Update compatibility
- General: Windows 10 1903 Update compatibility
- General: Fixed activation issue in Windows hosts set to non-English language (e.g. Cakewalk)
- General: AU: Fixed issue with increased CPU and memory on reopening UI
- General: VST3: Fixed issue with adapting to host knob mode, and now prioritizing linear
- General: VST3: Fixed issue with VST3 preset permissions
- General: VST3: Improved synchronization between parameter states and some UI functions, e.g. toolbar reset
- Fixed artifact when switching between LR and MS modes
- Fixed GR meter not being shown in Pro Tools
- Fixed UI coloring not being saved with session

Version 1.0 (Jan 9, 2019)
- Initial Release