Everything You Need to Know About Mix Bus Processing
When I first started mixing, I remember thinking: “How do I know when my mix is done?”
Each of the individual tracks sounded good on its own, but my mix just didn’t sound finished.
It was missing something. It still sounded like a recording instead of a song. It didn’t have that professional polish.
That’s where mix bus processing comes in.
In this blog, we’ll teach you everything you need to know about mix bus processing. Keep reading to learn what plug-ins and settings to use to give your tracks that radio-ready sound.
What Is Mix Bus Processing and Why Should I Use It?
Mix bus processing is just a fancy word for fine-tuning your mix as a whole.
Instead of adjusting individual tracks, you use tools like EQ, compression, and saturation on the whole mix. It’s kind of like pre-mastering.
It’s the cherry on top of your ice cream sundae. It’s the coat of polish on your new guitar.
Mix bus processing can be used to tweak the tonal balance of a mix. Or “glue” tracks together with compression for a more cohesive feel. It can even be used for adding automation.
The key to mix bus processing is to use gentle settings. Since mix bus processing affects your whole mix, it can be easy to over-do it.
As they say; “with great power comes great responsibility.”
Just because you can affect the mix doesn’t mean you should. You shouldn’t use mix bus processing to try to correct problems in your mix—just go back and fix them!
For instance, if you notice that the kick drum has too much low-end, just go EQ the kick drum instead of the mix bus. That way you don’t also cut the low-end on the other bass instruments in your mix.
Instead, you should use mix bus processing to turn a good mix into a great mix.
How to Set Up A Mix Bus
Setting up a mix bus is easy. Some DAWs even do it automatically.
Simply create a new auxiliary channel or bus and name it Mix Bus. Then route the output of each channel to the input of the Mix Bus.
If you’re already using busses for other channels, just route the output of each instrument bus to the Mix Bus.
Add plug-ins to your new Mix Bus whenever you need to tweak the sound of your whole mix.
Now that you know how to set up a mix bus, it’s time to break down the most common mix bus processing plug-ins.
Most of the frequency balancing should be done in the mixing stage. But it’s not uncommon to make a few small tweaks here or there on the Mix Bus.
EQ can be used to tame overpowering elements, like boomy kick drums. Or enhance pleasing elements, like shiny cymbals.
Just remember, small EQ moves make a big difference on the Mix Bus. Don’t boost or cut more than 3dB, and be sure to use soft, gentle shapes for subtle changes.
If you need to make any surgical changes, address the issue on the individual track.
Try using a low shelf to boost the bass for a little extra oomph and a high-pass filter to remove unwanted subs.
Cutting any mud around 200 Hz, or boxiness around 400 Hz is often best done with a dynamic EQ. We've got a complete guide to that here.
Add a little sparkle to your tracks with a high shelf boost around 8-12 kHz.
If you’re having trouble identifying which remaining frequencies to cut and which frequencies to boost, try using REFERENCE to compare your track to professional mixes. REFERENCE takes the guesswork out and shows you exactly which frequencies you need to adjust.
The most common problems typically occur in the bass frequencies, which is why BASSROOM is perfect for mix bus processing. Not only does BASSROOM compare your track to professional mixes, but it also makes suggestions on how to get the low end to sit right.
Once you have the tonal balance of the track locked in, it’s time to glue things together with a little compression.
Mix bus compression is all about “gluing” tracks together. It helps maintain consistent levels, prevent peaking, and increase excitement.
The key to mix bus compression is subtlety. Try a ratio of 2:1 to gently compress your mix as a whole and softly squeeze the instruments together.
Use a slow attack time (around 30 ms) and a fast release time (less than 50 ms) for maximum transparency.
Try not to apply more than 2 dB of compression. Any more than that and you run the risk of changing the dynamic balance of the track.
Compressors with side-chain filters work well because they ignore low-end frequencies that are likely to dive-bomb the meter.
If you plan to use a bus compressor, it’s important to insert it before you start mixing. There’s no point in spending hours getting the dynamics just right if you’re going to slap a compressor across the whole track and rebalance everything at the end.
PUNCH makes it easy to quickly dial in more smack into your mix using a few simple controls. It works especially well for accentuating high-frequency transients.
Once you’ve got a thick coat of glue on your mix, it’s time to add some grit!
OK, I know I’ve said this like three times now, but seriously—be gentle.
Take it easy with the saturation plug-ins. A little goes a long way. You just want to add a little harmonic saturation to make things sound more exciting.
The idea is to simulate the subtle distortion created by analog recording equipment—from tubes to tape machines to transformers.
If you’re looking for an authentic analog vibe, check out Mastering The Mix plugin IGNITE. It lets you dynamically add rich harmonic distortion based on your input signal—just like a real tape machine!
Last but not least, it’s time to add the finishing touches to your mix.
The mix bus is used to enhance your mix in every way. Lower lows, higher highs, more dynamic… dynamics.
The last piece of the puzzle is adding space. It’s not recommended to add reverb to your whole mix, as it makes it sound like the music is being played in a gymnasium.
Instead, try increasing the width with stereo widening plug-ins like GROW. Hone in on the high frequencies and instantly increase the width of your mix.
The Mix Bus isn’t just for bells and whistles. It’s also used to measure your audio levels to identify technical issues in your mix.
LEVELS gives you visual feedback on your peak and LUFS levels, stereo field info, dynamic range and more.
Think of this as the final quality control portion of your mix. It’s always best to double-check your meters before bouncing that final mix!
Mix Bus Templates
Many engineers use the same or similar mix bus processing on every track—almost like a sonic fingerprint.
After finding a signal chain that helps you achieve the sound you want, save it as a template and load it into your session before you start mixing. That way, you can mix into the mix bus for more nuance and control.
With this approach, your plug-ins are there from the start so you can push your signal up against the processors for a more exciting sound.
Some engineers prefer to put their mix bus processing on last. This approach works well if you only need a few touch-ups and you know exactly what you’re looking for.
Just be careful—I ruined plenty of mixes when I was starting by adding mix bus processing at the end.
That’s it! Those are the secrets to mix bus processing. Here’s a quick recap of our Mix Bus signal chain:
- EQ to remove unwanted elements and enhance pleasing elements
- Compression to “glue tracks together”
- Saturation to add excitement or create a classic analog vibe
- Stereo widening to add space
- Metering plug-ins to monitor technical issues
Brad Pack is an award-winning audio engineer and writer based in Chicago, IL. He currently owns and operates Punchy Kick, a professional mixing and mastering studio that specializes in pop-punk, emo, punk, grunge, and alternative music. When he’s not in front of his laptop, Brad can be found gaming with his wife, spending time with his son, or throwing down in the mosh pit.