Introduction
The SM Switcher is a plugin specifically made for learning audio mastering. It offers an easy way to switch between two different audio sources with automatic loudness matching. This makes it possible to avoid loudness bias when comparing your master to the original mix.
Loudness bias is when you tend to perceive louder as better and makes it very difficult to make useful decisions when mastering. In our experience it is much easier to learn mastering when your feedback loop includes the actual differences without any loudness bias. That is the main purpose of this plugin.
The SM Switcher also has useful monitoring features like Mono, Solo Left/Right etc.
Prerequisites
The SM Switcher is available for Windows 10/11 and macOS (Monterey 12.6.3 and upwards).
The plugin is in VST3 (Windows/macOS) and AU (macOS) formats and should be usable in any DAW compatible with those plugin formats. The plugin has two stereo inputs, which in some DAWs will be shown as the Main Input and the Sidechain Input. In order for the SM Switcher to work properly your DAW needs to support plugins with two stereo inputs, or a stereo input + stereo sidechain.
Instructions for setting up the SM Switcher in Reaper and FL Studio can be found in this manual. We are working on instructions for more DAWs. Make sure to try the demo in your own setup before purchasing a license.
Installation
Close your DAW software, run the installer by double clicking the installer file in Explorer (Win) or Finder (Mac), and follow the instructions.
Using the SM Switcher
Where to place the SM Switcher plugin
The SM Switcher is primarily designed to be used for monitoring. You will normally not use the plugin for processing audio within the mix itself and it should not be used in a way that lets it affects any exported or rendered audio.
Other types of monitoring plugins are things like calibration plugins for speakers or headphones, or cross feed plugins for headphone monitoring. You will generally use the SM Switcher plugin in the same chain as any of those plugins. You will generally place the SM Switcher before cross feed and calibration plugins, and after any meters or measuring plugins.
Some DAWs (for example Reaper) have dedicated plugin chains for monitoring plugins. The main advantage of having a separate plugin chain for monitoring is that these plugins will never affect the rendered audio.
For DAWs without a dedicated monitoring chain (for example FL Studio) you will either need to remember to disable any monitoring plugins before exporting, or use a work-around solution by setting up your own monitoring chain.
Routing the signal to the SM Switcher
The SM Switcher has two stereo inputs and one stereo output. The inputs are named “Main input” and “Input 2” and these names are shown by some DAWs. The big buttons labeled “1” and “2” selects which one of the inputs that is heard at the output of the plugin.
When you insert the SM Switcher in a plugin slot in your DAW, the input signal will by default be routed to the Main input, and it will be audible when Input 1 is selected. You can route another signal to the second input of the SM Switcher in the same way as you would send a signal to the sidechain input of a compressor plugin. The exact procedure for using sidechain inputs varies between different DAWs and is usually found in the manual of the DAW.
Three common use cases for the SM Switcher are:
- Routing the master to Input 1 and the unprocessed mix to Input 2. This makes it easier to compare before/after when mastering.
- Routing the master or mix to Input 1 and a reference track to Input 2. This makes it easier to compare the master or mix to a reference track while mastering or mixing.
- Route the mix with mix bus effects to Input 1 and the raw mix to Input 2. This makes it easier to compare the mix with and without mix bus processing while mixing.
How to use the Automated Loudness Matching
The ALM (Automated Loudness Matching) is the core feature of the SM Switcher. It ensures that different audio sources, such as your master and original mix, can be compared at perceptually equal loudness levels. This allows for unbiased A/B listening, by pressing the big 1 and 2 buttons, without being misled by volume differences.
The short version of how to use the SM Switcher with ALM effectively is to follow these steps:
- Enable ALM.
- Select Input 1 and press play.
- Give the ALM a few seconds to measure the loudness of the two inputs.
- Look at the ALM meter and adjust the trim level of Input 2 so that the yellow bars fall within the green area.
- Now you can switch between the two inputs and the loudness will automatically be matched.
- You may need to re-adjust the trim level if the yellow bars fall outside of the green area, which will then turn red. Follow the same procedure as above.
- If the yellow bars are out of reach when using the trim level of input 2 you can also adjust the trim level of input 1 to lessen the loudness difference. If the yellow bars still are out of range you will need to adjust the level at the source instead, i.e. tweak the levels before the signals reach the SM Switcher.
We recommend that you get to know the plugin by following the above steps. The next part of this manual will explain how the ALM works in more detail.
How it works – in more detail
The ALM operates in two stages:
- Manual loudness matching using the trim sliders
- Automated fine tuning via the ALM engine, within a ±3 dB range
The ALM Meter shows the difference in loudness between the two inputs. This meter will guide you into setting the correct manual trim levels and make sure that you get the optimal range for the automated loudness matching.
The ALM Meter has three short horizontal bars; two yellow bars on each side and one green bar in the centre.
The yellow bars show the current loudness difference between the inputs. They basically show where the trim level needs to be set in order to match the loudness. The left yellow bar is based on a long-term measurement, and the right yellow bar is based on a short-term measurement.
The green bar in the middle shows the current gain applied to input 2, which is the sum of the manual trim level and the ALM gain. The ALM will try to compensate for the short-term loudness difference and can adjust the gain within ±3 dB. The available range is shown in the ALM meter as an area around the green bar.
The ALM range area can have different colors:
- The area is green while you are listening to Input 1 and the needed compensation gain is within the ALM range.
- The area is red while you are listening to Input 1 and the needed gain is outside of the ALM range. Adjust the trim levels to bring the yellow meters within the range.
- The area is dark yellow while you are listening to Input 2. Whenever you switch to Input 2 the automatic gain will freeze to the current value. This is to avoid that the level fluctuates while you are listening to Input 2. The loudness difference is still measured and visible via the yellow meters.
- The area is dark grey when playback is stopped.
Setting the Output Level
The compensation gain of the ALM together with the manual trims can result in peak levels above 0 dBFS after loudness matching. The border around the Output Level will flash red if the output signal exceeds 0 dBFS. In order to avoid clipping you can decrease the Output Level.
The default value for the Output Level is -8 dB, which creates 8 dB of headroom for the manual trim and Automatic Loudness Matching before there is any risk of clipping. This is usually enough, considering that there is up to +5 dB gain from the manual trim plus up to +3 dB of gain from the ALM, in total a maximum of +8 dB gain.
⚠️ Note that lowering the Output Level makes the output of the plugin quieter than the input when enabled, so beware of this difference in loudness if you should bypass the plugin.
Stereo monitoring features
Mono and Pol
Mono sums the left and right channel so you can listen to the mono signal. Pol flips the polarity of the right channel and makes the signal appear “out-of-phase”. This can sometimes be good for troubleshooting, but it is most useful together with the Mono button since pressing both of them will let you hear the Side (Difference) signal.
Flip L/R
Flips the stereo image, i.e. lets left and right trade places. Makes it super easy to check if the stereo image is tilting to the left or right.
Solo L/R
Solos the left and right channels respectively. Use it together with the Mono button to quickly hear any tonal differences between the left and right channel.
Help and info
Press the Help button to enable helpful tooltips for most controls.
Press the Info button to see more information about the plugin.
Setting up in Reaper
The goal with this section is to add the SM Switcher plugin to Reaper’s Monitor FX chain, add two tracks in the arrange view, and route the output of the tracks to the two inputs of the SM Switcher plugin.
Step-by-step
1. Add the Plugin to the Monitoring FX Chain
Open the Monitoring FX Chain from the top menu “View → Monitoring FX”.
Add the SM Switcher to the plugin chain. If you have other monitoring plugins in the chain, make sure to add the SM Switcher before any speaker/headphone calibration or cross-feed plugins and after any measuring plugins, like LUFS meters or spectrum analyzers.
Open the Plugin pin connector window and make sure that “Track channels” is set to 4 or more. Note that in Reaper you can have up to 128 channels in the Monitoring FX chain, no matter how many outputs your audio interface actually has.
If your audio interface has more than two mono outputs, and you want to use the third and fourth output channels for other things, then you can route the signal via any other two channels. Remember what channels you chose here, you will need them soon.
2. Create and route tracks
Create two tracks in your Reaper project. You can name them however you want, for example:
Track 1: Master
Track 2: Original Mix
Click the “Route” button on Track 1.
Ensure Master Send is enabled. This sends audio to Channels 1–2 by default, which go to Input 1 of the SM Switcher. Close the routing window.
Click the “Route” button on Track 2.
Disable “Master Send” (you don’t want it going to Inputs 1-2).
Under “Add new hardware output”, select “Spare 3 / Spare 4” (or Channels 3/4, depending on your system’s naming) OR select the same outputs as you chose earlier when you added the plugin to the Monitor FX chain. This sends the audio to Input 2 of the SM Switcher.
Now you have two tracks, routed to the two inputs of the SM Switcher. Place the audio items you want to listen to onto each of the tracks. You can for example work on your master on the top track and keep a copy of the original mix on the second. Then you can easily do loudness matched comparisons between the master and the mix using the big 1 and 2 buttons on the SM Switcher. Save the project as a template in order to quickly get started in the future.
Setting up in FL Studio
FL Studio doesn’t have a dedicated monitoring plugin chain. This means that in order to use plugins that are meant for monitoring only, like the SM Switcher, you will need to adapt some kind of work-around. This also applies for other monitoring plugins like room/headphone correction or cross-feed plugins.
There are basically two ways to use the SM Switcher in FL Studio: 1. On the master track or 2. On a separate monitor track. We will describe both options in this manual.
The first option, placing the SM Switcher on the master track, is the easiest to set up but has some disadvantages. As the SM Switcher is a monitoring plugin, you will need to remember to disable it before exporting your master files.
The second option, using a separate monitor track, has a more complicated setup but also has big advantages in the long run.
Option 1: Put SM Switcher on the Master track (easiest)
With this option you will get a simple setup that can be great for learning or doing a quick A/B. The main downside is that since it’s on the Master, you must bypass/disable SM Switcher before exporting and enable it again afterwards.
Step-by-step
1. Insert SM Switcher on the Master
- Open the Mixer (F9).
- Select the Master track.
- In the last FX slot, load SM Switcher. If you are using other monitor-only plugins like room correction or cross-feed for headphones, then the SM Switcher should be placed in a slot directly before/above these plugins.
2. Create a REFERENCE track and sidechain it to the Master
- Pick an empty mixer insert and name it REFERENCE.
- Select the REFERENCE mixer track, right-click the small arrow on the Send control switch on the Master, and select “Sidechain to this track”.
3. Map the sidechain input into SM Switcher
- Open SM Switcher on the Master and click the Plugin Wrapper settings (the gear icon / wrapper menu).
- Click the Plugin options button.
- Go to the Processing tab.
- Enable Input 2.
- Select “REFERENCE” as the source for Input 2.
Now when Input 1 is selected in the SM Switcher you will hear your master output, and when Input 2 is selected you will hear whatever is routed to the REFERENCE track. This could be your mix without master processing, a different mix version, a reference song or anything else that you want to use for comparison.
⚠️ Export reminder (important) ⚠️
- Before exporting:
- Lower the level of your speakers or headphones. This is to avoid a loud surprise if you forget to re-enable the SM Switcher after exporting.
- Go to the Master track.
- Bypass/disable SM Switcher (and any other “monitor only” plugins), then export.
- After exporting:
- Go to the Master track.
- Enable SM Switcher (and any other “monitor only” plugins).
By default, the SM Switcher lowers the output level by 8 dB. This is to provide enough headroom to do loudness matched comparisons without clipping the output of your audio interface. After exporting, you must remember to enable the SM Switcher again, otherwise the output may be quite a lot louder than you expect when hitting play.
Option 2 — Use a separate Monitor track
With this option you can keep monitor-only tools (SM Switcher, headphone calibration, cross-feed, etc.) off your render path. This means that you don’t need to disable these plugins before exporting.
Step-by-step
Images coming soon.
- Create a MASTER track that everything routes into. This is where you will place any master effects. Note that this track is separate from the main “Master” bus in FL Studio.
- Create a MONITOR track that will host the SM Switcher (and any other monitoring plugins) and be used as the output to the audio interface.
- Make sure the MONITOR track does NOT feed FL Studio’s main Master bus.
- Create a REFERENCE track that will be used for routing signal to the second input of the SM Switcher.
- Route MASTER → FL Studios main Master bus.
- Route MASTER → MONITOR.
- Route REFERENCE → MONITOR as Sidechain.
- Put SM Switcher on the MONITOR track and select REFERENCE as the source for Input 2
- Set the output of the MONITOR track to the main output of your audio interface.
- Set the output of FL Studios main Master bus to “None”.
Now when Input 1 is selected in the SM Switcher you will hear everything that is routed to the MASTER track, and when Input 2 is selected you will hear whatever is routed to the REFERENCE track. This could be your mix without master processing, a different mix version, a reference song or anything else that you want to use for comparison.
Note: Avoid adding plugins to the main Master bus when using this setup, other than meters or other plugins that don’t alter the sound. Plugins on the master bus will be included in the export, but will not be audible through the monitor bus.