FCP X: Boost and Smooth Audio Levels

Posted on by Larry

You ever have a problem where the audio levels you recorded for your talent are too low, or vary wildly in level? Yeah, me too. All the time. We can add audio keyframes to each clip and try to smooth things out, but, frankly, life is too short.

A while ago, I discovered some audio effects that can make this task a LOT easier. In this article, I’ll show you how they work in Final Cut Pro X. (In a second article, I show how they work in Adobe Premiere Pro CC.)

NOTE: Personally, while the audio processing effects in both FCP X and Premiere aren’t too bad, I find that the precision and control Audition provides is superior to both. While learning an audio app can be intimidating, the time you invest pays major dividends in making your audio sound really, really good. (Here’s a link to my training on Adobe Audition.) ProTools is another excellent audio package, but I’ve never had success working with their iLok copy protection.


The Limiter effect is my tool of choice in FCP X for boosting and smoothing levels.

Because effects process before audio settings in the Inspector, we need to collect the audio we want to control into a compound clip then apply the limiter effect to the compound clip.

Also, while it is a good idea to boost and limit dialog, interviews and narration, it is generally not a good idea to do the same with either sound effects or music.

NOTE: Here’s a companion article I wrote that is the second half of the “good audio” equation: using EQ to shape your sound to make it warm up a voice and make it more intelligible.


The human voice is unquestionably a challenging instrument to record. Whether singing or speaking, it has a huge dynamic range; meaning that it can vary from loud to soft back to loud in an instant. Sometimes, when you are working with professional voice actors, that dynamic range is fully under control.

Most of the time, we’re just hanging on for dear life.

There are two key rules you need to keep in mind about audio when you are mixing:

  1. At NO time during export should your audio levels ever exceed 0 dB. Not once, not even for “a little bit.” Never.
  2. Audio recorded on set is always recorded at lower levels so that there’s no risk of distorting an irreplaceable take.

This means that during our final audio mix, we need to boost soft levels, make the levels consistent so that we can clearly hear what’s being said, yet make sure all levels always stay below 0 dB.


Audio pros, and those folks that need to deliver audio for professional distribution (broadcast, cable, or digital projection), measure levels using “average levels,” or the new standard of LKFS. Current standards in both the US and Europe mandate that levels not exceed a specific LKFS for program content; generally around -24 LKFS.

Final Cut Pro X does not provide built-in meters for measuring average levels, though they can be added using plug-in effects from MeterCast and Waves; among others.

For this reason, this article will talk about “peak” levels, which are suitable when mixing audio for web posting. Final Cut measures peaks using dBFS; which stands for “deciBels Full Scale.”

NOTE: Premiere and Audition both provide LKFS and peak audio level measurement built into the application. This is one of the reasons I prefer using Audition for my mixes, rather than Final Cut.


Here’s a portion of a short dramatic scene. It has a sync dialog track, three effects tracks, and one music track. (This technique can be used for far more clips and tracks, I’m just keeping this simple to explain the process.)

To get an example of our audio levels, I selected just the dialog clips.

Then, I clicked the Solo button in the top right corner of the Timeline.

Soloing allows me to hear the selected clips, but nothing else. (Notice that the dialog clips retain their steel blue color, while the muted clips became black and white.)

NOTE: Soloing has no effect on video clips.

When I played them, the selected audio levels peaked around -20 dB. This is WAY too soft for principle dialog!

Since the dialog clips are selected, it is easy to bundle them into a compound clip. (Choose File > New > Compound Clip). Give the compound clip a name – I used “Drama SOT Audio” – and save the clip. The selected clips in the Timeline are now replaced by the compound clip.

Now that we’ve prepped the clips, it’s time to apply and adjust the Limiter effect.

NOTE: You can still access the individual clips in a compound clip by double-clicking the compound clip. This opens it for editing.


What the Limiter effect does is boost softer passages of audio more than louder passages, without having any audio level exceed the maximum level you specify in the effect. (Hence, the name: this effect “limits” how loud your clips can get.)

In our example, limiting has the effect of making all dialog levels louder and more consistent, without any risk of distortion.

There are two limits that I recommend:

NOTE: The reason I don’t limit to 0 dB is that I’ve been told that MP3 compression is optimized for levels around -6 dB. Also, leaving a bit of headroom is a good idea in general.


Select the compound clip, if it isn’t still selected, and open the Effects Browser (Cmd+5). Scroll down and select the Levels category. Drag the Final Cut Limiter effect on top of the selected compound clip.

This applies the effect to the group of clips contained by the selected compound clip.

NOTE: You could also apply this effect to individual clips. The problem is that you would need to adjust the settings of this effect for each individual clip. Using a compound clip allows you to apply the effect once and have it apply to all clips included in the compound clip.

Again, with the compound clip still selected, click the Audio text button at the top of the Inspector. Click the small icon to the right of the Limiter parameter.

This opens the Limiter effect interface. Four of the settings are generally set to the same values:

The one setting you need to adjust each time you use the filter is Gain.

Here’s the secret to adjusting the filter. Play your clips. Then, while the clips are playing, adjust the Gain so that the Gain Reduction setting, at the top, is bouncing around 1 – 3 dB. This provides maximum amplification, without excessive limiting, which can sound fat and “blatty.”

That’s it. Try this and you’ll be amazed at how much better dialog, interviews and narration can sound.

NOTE: Remember to adjust the filter when all other tracks are silent or muted.


In some cases, you’ll still need to adjust some clips which are a bit loud or, more likely, a bit soft. The good news is that now, you are adjusting for the exceptions, rather than everything.

What I generally do is open the Compound clip and adjust the clips inside as necessary. I almost never apply keyframes or adjustments to the Compound clip, just the clips inside it.


I am a huge fan of the Limiter effect and its cousins, the Compressor and Multi-band Compressor, because they simplify the process of setting levels and preventing distortion. While I like compressors, I’ve found that in Final Cut, the Limiter effect is easier to use.

While I do move complex mixes into Audition, for simple projects like this, creating compound clips and applying the Limiter effect makes my audio life easy and helps me get projects done on time and without excessive audio stress.

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32 Responses to FCP X: Boost and Smooth Audio Levels

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  1. David Farquhar says:

    Thanks for this post it has really helped me. Am I right in thinking I don’t have to worry too much about the audio levels in the underlying clips, provided they are all correct relative to each other? So if the original clip is recorded too loud, I don’t have to adjust it provided I’m happy with the limiter reducing all the over loud parts down to -4.5db (or whatever else I’ve set)?

    • Larry says:


      Well…. you’re an editor – you should always worry.

      If your underlying clips are distorted, the Limiter won’t help. If, however, your underlying clips are not distorted, then the Limiter – if applied to the Master track – will make sure the final mix is not distorted.

      However, don’t think of this as a magic button – you still need to get the relative levels of your clips to sound good. The Limiter is a final guard against an errant level. Creating the mix is still your responsibility.


  2. CLD says:

    Hello Larry,

    Thanks for these articles. I have applied your knowledge to a few clips and they work very well, but I am stuck on one in particular of which I don’t understand the behaviour and how the settings apply to it. Screenshot here:


    After applying the Limiter filter (while keeping the clip volume to 0), its Gain Reduction slider already peaks over -10 db which you say is too much amplification, but the green meters are below -6 and the audio is quite low (I am not editing on an ideal setup – I am using an iMac, and keeping its volume setting in the middle because I thought that would be as neutral as possible and where I would like to hear things properly without having to increase it to the maximum).

    I am wondering if, after the limiter has been applied, it is ok to raise the Volume level of the clip in the Audio inspector, ignoring the blue Gain Reduction slider in the filter, or if there are better ways to raise the volume once the limiter filter has been applied.

    Thank you very much for these articles and your time.

  3. Kris says:

    Thanks for this, it SAVED me! You’re awesome!

  4. […] Larry provides some wonderful guides for the Final Cut Pro X workflow. One of the best is the Boost and Smooth Audio Levels. You can follow his workflow and even out those […]

  5. Hans Douma says:

    Hi Larry,

    My FCPX is not showing me the Limiter effect. It’s just not there. What am I missing ?

  6. Hi Larry,

    I use FCPX 10.3.4 and I’m trying to raise the low audio levels of my clip, while restricting its highs so that it does not exceed 0. My audio clip (an MP3) was recorded using one H1 zoom recorder at an input level of 50 at about a foot from its (two) speakers.

    When I followed your Limit Effect recommendations, I received little or no Gain Reduction, with the exception of when the two narrators raised their voices. In any case, I’m interested in attained a clear, balanced sound and I hope you might help me.

    I’d be more than happy to send you my MP3 file. Feel free to respond publicly or privately to my work email.


    – Marc

    • Larry says:


      Thanks for writing.

      If your audio is too low, it won’t hit the top end of the limiter. Remember:

      * To prevent distortion, don’t boost the clip level, just apply the Limiter filter
      * Increase the limiter gain so that you see it “rejecting” 1-2 dB in the Reduction display. The maximum you can raise the level is 20 dB. For some really soft clips, this won’t be enough.
      * Be sure the Limiter filter is the last audio filter you apply. Putting EQ AFTER the filter destroys the “limiting” the filter provides.
      * I generally recommend setting the Look Ahead to the smallest level possible, with the Release set to 500 ms.
      * Set the Output to -3 dB.


  7. Bill Rabkin says:

    This technique (applying and adjusting the audio Limiter effect) still works as described, but in an FCPX update Apple significantly changed the UI.

  8. Tiff says:

    I so hope youll be able to do an update to this for the newer UI. Theres a couple of features that dont seem available but mostly that your how to is the only one with this instruction. Its most helpful even if harder to implement for the novice due to chnages. The main thing, the Gain Reduction Display is no where to be found now. I have web searched and apparently not even FCPX thought it was necessary to provide guidance on its location. I’m having to guess on my Gain levels now.

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