What do you see when you look at the Level Meters of a Channel Strip in Logic Pro X? It might be the pre-fader signal or the post-fader signal. Or, it might be something completely different ... as you will find out in this article.
To properly use any meter or gauge, you not only need to know what the displayed value is but also where the value was measured. For example, if the dashboard of a car displays a temperature value of 30°C, then you also need to know whether that value was measured inside the car, outside the car, or at the engine. Otherwise, you cannot do much with that information. The same thing is true for any type of meters in Logic Pro, especially the Level Meters on the Channel Strip and Track Header.
The Level Meter is displayed on the Track Header ➋ in the Tracks Area and on its corresponding Channel Strip ➊ in the Mixer Window.
Meter Appearance The Level Meters on the Track Headers and Channel Strips show the same value for a Track, but they differ in their appearance:
- Channel Strip ➊: The meter is longer and has a scale ➌. The value box above shows the peak value ➍ (in dB), which will be reset when you start playback or click on it.
- Track Header ➋: The horizontal meter has no scale, is shorter, and gets even shorter when you resize the Track Header horizontally. ➎ At its minimum size, the meter changes into a single LED that can only have three colors ➏, gray (no signal), green (signal), and orange (clipped signal).
Meter Characteristics Don't forget to check the Display Preferences in Logic Pro. The Mixer tab has a section specifically for Level Meters ➐ to set their characteristics:
- Peak Hold Time: The meter segment of the highest level (peak) stays on longer after the level decreases. With these options, you can determine for how long.
- Return Time: The dB/s is basically a speed unit that determines how fast the meters go down when the level decreases. In other words, you can select from the popup menu how "busy" the meters appear.
- Scale: The "Sectional dB-linear" ➑ option is selected by default, but if you need a higher resolution in the upper meter range, you can choose the "Exponential" ➒ option. The screenshot on the right shows the same -20dB level displayed on the two scales.
- Channel Order: This selector lets you choose from four different surround sound formats that determine what channel is displayed by what meter bar.
Logic Pro X, like most DAW's, has a mode called Pre-Fader Metering. It determines where the signal level will be measured along the signal flow on a Channel Strip.
- Enabled (pre-fader) ➊: If the mode is enabled, the signal level will be measured right before the Volume Fader (after the Audio Effects). The meter bars ➋ are displayed to the left of the Volume Fader ➌. This mode has the advantage that you can see if a level is really hot (regardless of the Volume Fader position), which could cause problems with some plugins that require a specific signal level range.
- Disabled (post fader) ➍: If the mode is enabled, the signal level will be measured right after the Volume Fader and Mute Button (before the Pan Control). Now, the meter bars ➎ are displayed to the right of the Volume Fader ➏ to reflect the order in the signal flow.
You can toggle the Pre-Fader Metering Mode in three ways:
- Control Bar ➐: Click on the Pre-Fader Metering Button in the Control Bar. This button has to be made visible in the Control Bar Configurations Popover (Main Menu Window ➤ Customize Control Bar and Display...).
- Menu Command ➑: Select from the Main Menu Mix ➤ Pre-Fader Metering.
- Key Command ➒: You can use the Key Command "Toggle Pre-Fader Metering", which it is not assigned by default.
The Third Option!
And finally, here is the most important part of the Level Meters. In addition to measuring the signal level before or after the Volume Fader, the Level Meters on Audio Channel Strips can show you the level on a third point of the signal flow and ignore the Pre-Fader Metering Mode. Look at the following signal flow diagram of Logic Pro's Audio Channel Strip that shows what signal is routed to the Level Meter.
These are the three measuring options:
- Pre-Fader Metering
This measuring point ➊ reads the audio signal before the Volume Fader, but after the Audio Effects. It is the same level that you send to a Pre-Fader Aux Send ➋ (please note that the Aux Send included the Mute Button status).
- Post-Fader Metering
This measuring point ➌ reads the signal after the Volume Fader (and Mute Button), but before the Pan Control. It is the same level that you send to a Post-Fader Aux Send ➍.
- Input Metering
This third measuring point reads the actual Input signal ➎. It is the audio signal that is coming from the external Audio Interface ➏, "entering" into Logic (before any Audio Effects on your Insert Slots) to be recorded onto an Audio Track ➐ as an Audio Region. The Level Meters are automatically switched to this "Input Metering Mode" whenever you enable either the Input Monitoring Button or the Record Enable Button. Please note that, although the Pre-Fader Metering Button now has no effect on the Level Meters, it still switches the position of the Level Meters to place them to the left or right of the Volume Faders on the Channel Strip.
As you can see on the signal flow diagram, the audio input in Logic (that the Level Meter is now measuring), is identical to the audio output of the audio channel that you are recording from the Audio Interface ➏. At this point, the signal is a digital audio signal and when you see clipping on the Level Meter in Logic Pro, it indicates that the clipping is happening "outside", or "before" Logic Pro. That means the Audio Interface is clipping, not Logic Pro. Logic's Level Meters only "report" that you have an issue on the external Audio Interface and you have to turn down the Input Gain ➑ on the Audio Interface (not Logic!) because Logic doesn't have an input gain knob ... or does it?
Remember the Audio Device Controls knob ➒ on top of the Audio Channel Strip. This is technically an Input Gain control. However, instead of adjusting the incoming signal in Logic Pro, it lets you remotely adjust the input gain on the external audio interface (a feature that has to be supported by the manufacturer).
So technically, while in Input Metering Mode (enabled Input Monitoring Button or Record Enabled Button), you are measuring the output ➓ of the audio interface, the specific channel you are feeding into the Audio Channel Strip.
Graphically Enhanced Manuals
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For an up to date list of my "Graphically Enhanced Manuals (GEM)" series and all the links, go to my website.
Thanks for your time and interest,