Using Compression on Your Master Fader

Mix bus compression. Do you do it? Should you do it?

First off, let me explain what I’m talking about. When you’re mixing a song, regardless of what DAW you’re using, all of your audio tracks are being fed into a single mix bus. This is normally represented by a master fader of some sort.

When you’re first starting out mixing, you’re main goal is to mix everything at a decent level without clipping your master bus. As long as you’re happy with your mixes, you can keep doing this…and you don’t have to read the rest of this article. ;-)

However, a lot of mix engineers use some sort of compression on the master bus. They’ll slap a compressor or limiter on the master fader. There are several reasons to do this…and not all of them are necessarily “good” reasons. Let’s take a quick look at a few examples of why you might want to use compression on your entire mix.

Scenario #1 – You’re client wants a demo CD to play in the car.

This is a common request. You finish up a recording session, and before the artist goes home, she would like to take something with her to listen to between now and the next session. (If you’re an artist, you know what I’m talking about. You just want something to listen to, right?)

In this situation, you could simply do a bounce of the song, burn it to CD and send her on her merry way. However, chances are your phone will ring thirty minutes later, and she’ll say, “Something’s wrong with this recording. It’s too quiet! It doesn’t sound as loud as my other CDs.”

What your client may not know is that the audio on a finished, mastered CD has gone through a LOT of compression. Her music will need to be both mixed and mastered before it will be at a relatively “normal” volume.

You can try to explain this to her, and explain why it’s not a faulty recording, but there’s the chance she may start to doubt you a little.

I know, I know. This is probably an extreme example, but it can certainly happen. For this reason, a lot of engineers will simply throw a compressor and/or limiter on the master bus right before bouncing the song down for the client. Since the client knows it’s a rough mix, she won’t expect it to sound perfect, but at least it will be plenty loud.

Scenario #2 – You want your mixes to sound like they’ve been mastered.

In the first scenario, we applied compression/limiting to the mix for the sake of the client, NOT the mix.

However, as you’re working on a project, and listening to your various mixes, you may get the urge to squash them with some compression and limiting to make them sound more like a “polished,” finished, mastered recording.

Here’s where things can get dangerous. Now you’re changing the sound of the mix. Mixing and mastering were meant to be two completely independent phases. When you start trying to mix AND master at the same time, you’ll inevitably do a poor job of both.

What ends up happening is you use too much compression, and you begin to rely on the compressor and limiter to achieve that “sound” you’re going for. This is a backwards work flow. You should use the normal methods of mixing — EQ and compression on individual tracks, effects, automation, etc. — to make your mixes sound good. As soon as you start relying on the mix bus compression to save you, you’re going down the wrong path.

This isn’t to say you shouldn’t use ANY compression during mixing, but you need to be clear as to why you’re using it. Keep mixing and mastering separate.

Scenario #3 – You want something to help “glue” your mixes together.

This scenario describes what I try to do when I mix. I almost always use a compressor on the master bus. However, I’m not using it to compress the living daylights out of my mixes. I just use light compression (usually with a 2:1 ratio) to give me no more than 2-4 dB of gain reduction. That’s it. (My compressor of choice right now is the Waves SSL Bus Compressor, which is a part of their SSL Bundle.)

The reason I do this is because the compressor causes everything to “stick together” a bit better in the mix. It’s the glue that holds my mixes together. It helps my mixes sound more like a mix and less like a bunch of individual instruments.

A couple things to consider when using a bus compressor:

  1. Use it from the beginning. – You should instantiate your bus compressor VERY early in the mix process. Don’t wait until the last five minutes to throw it on there. If you do, the compression will essentially “undo” everything you’ve been working on for the past few hours. For example, you could have an amazing balance going on in your mix, but when you add a bus compressor, suddenly the lead vocal seems lost, and the shaker and high hat are too loud. Use the compressor from the beginning, so you’re making all of your changes while listening TO the compressed signal.
  2. Don’t use it “just because.” - If you’re happy with your mixes, don’t start compressing everything just because you can. It’s much easier to over-compress something and make it sound worse than it is to just leave it alone. Be very conservative with any bus compression you do.
  3. Don’t use a limiter. - Limiters should be left for the mastering engineer.
  4. Ask your mastering engineer. – Contrary to what some people say, a lot mastering engineers don’t mind if you send them a mix that’s been compressed a little bit. In fact, some say that it’s easier to master a song that’s been lightly compressed than one that hasn’t been compressed at all. Keep in mind, though, that if you go overboard with compression, you’re making the mastering engineer’s job much harder, and you’re giving him less room to work.

Do you use a bus compressor? Why or why not? Leave a comment and let us know. I need at least 10 comments from you folks (let me know you’re out there). ;-)

  • Ana Morgan

    I do not use bus compressor. But I compress tracks alone. I am trying to not over-compress. Any way I like compressor. I like EQ’ing as well :) Nice home page you have here, Joe! Thank you!!! Regards, Ana Morgan

    • http://www.homestudiocorner.com Joe Gilder

      Thanks Ana!

  • Sojcher12

    sweet just found this article and thought: “hey that sounds like what I do!” I use that SSL Bus compressor which I think is fantastic and use just a little bit of compression on my master to give me some “glue” and I never mix without it!

    • http://www.homestudiocorner.com Joe Gilder

      It’s great stuff, eh?

  • Stewee1092

    I noticed that all my mixes sounded a little quite like scenario one. I am throwing a compressor on my track now ( late in the mix :[ ) to get it sounding a little more professional, I’m only left the gr go to about 4 db max and I turn it off and on a lot to make sure I’m not screwing up my beautiful, but quite unglued, mix. thanks so much for the tutorial type thing, helped a lot!!!! 

    • http://www.homestudiocorner.com Joe Gilder

      You’re welcome. Thanks!

  • http://www.MasteringTuition.com Dave

    Getting back to the original subject…

    If you plan to use a mastering service, as in have a dedicated engineer process the master-bus, leave it free from any processing while you mix because the prcocesses you use will affect the decisions made by the engineer and can even limit the things he/she can do. If you insist on mixing with master bus compression to help your mix sound good, keep it to a very small amount.

    If you don’t plan to send your mix to a mastering house, go crazy, shove what ever you like on the masters!

    There are some very angry people on here and a pretty warped view of the responsibilities and skills of dedicated mastering engineers.

    I do agree that in a lot of cases, it makes perfect sense to do your own mastering. For anyone who is thinking of doing their own mastering, check out my website… http://www.MasteringTuition.com

    For anyone reading all these comments, I advise you go get a free sample and see what a dedicated mastering service can do for you. You might be pleasantly surprised.

    • http://www.homestudiocorner.com Joe Gilder

      Thanks Dave. I agree that IF you use compression on the master, then use only a little bit and use it the entire time you mix, from early in the process. Don’t just slap a compressor on at the end.

      As with all things mixing, don’t do anything “by default.” If you’re compressing the master bus, make sure you know WHY you’re doing it.