How to use Compression: Live Mixing With Dynamic Range

Live mixing can be a rollercoaster!

One moment you have a sweet mix, it’s nice, clean and crisp. Then the next moment your vocalists volume spikes because they start belting out. Leaving people’s ears ringing.

This is where compression comes in, and when it comes to live sound, it’s an absolute game-changer.

When I first tried using compression I had no idea what half the controls did. Once I figured it out though, my mixes went from chaotic to controlled.

Compression helps you smooth out wild dynamics, balance the instruments, and ensure your mix is polished, no matter what the room or band throws at you.

Let’s take a look at the basics and focus on how it can transform your live mixing experience.

What Is Compression?

At its core, compression is about controlling dynamics. More specifically, the difference between the loudest and softest parts of a sound.

In live mixing, that means controlling unexpected peaks and dips, especially from vocalists and loud instruments like the drums.

The compressor works by reducing the volume of louder sounds and boosting quieter ones to even things out. You can think of it as an automatic volume control.

It kicks in based on the settings you choose.

Historically, this was used sparingly in live sound due to the limitations of older analog gear, but with digital consoles, compressors are everywhere.

From vocal mics, bass guitars,or to the overall mix bus, compression is now an essential tool for any live sound engineer. It’s especially useful in places where you can’t predict what will happen on stage.

Like when a vocalist suddenly belts it out during the quietest part of a song.

We’ve all been there, right?

Understanding Key Compression Parameters

Now, if you’re staring at the compressor on your console and feeling overwhelmed, don’t worry!

Let’s go over the key controls and how they work in a live sound setting.

Threshold: This is the level where the compressor kicks in. If your threshold is set too high, you can miss the peaks that you want to control. If it’s too low, you’ll squash your sound too much and lose all the dynamics. When mixing live, I usually start with a moderate threshold to catch the louder peaks without making everything sound flat.
Ratio: Think of this as how aggressive the compressor will be. A 2:1 ratio means that for every 2 dB over the threshold, the output will only increase by 1 dB. For example, If you have a 4:1 ratio set up and a -10 dB threshold, and let’s say a vocalist gets up to 0 dB in loudness. Since 0 dB is 10 dB’s over, it will only let 2.5 dB go through. (10 dB divided by 4 = 2.5 dB).
Attack and Release: These define how fast the compressor responds to sound going over the threshold (attack) and how quickly it stops compressing after the sound falls below the threshold (release). Fast attack times are great for catching sudden peaks, but they can also dull the sound if set too low. Release times are tricky—too fast, and the sound will “pump” or breathe; too slow, and the compressor won’t release in time for the next note. It really depends on the style of music and the room’s acoustics on how you set these.
Knee: The knee setting affects how smoothly the compressor starts working. A “hard knee” means the compression kicks in suddenly, while a “soft knee” gradually increases compression as the signal approaches the threshold. For example, I like using a soft knee, especially on vocals, to keep things sounding natural.

What are Common Uses in Live Mixing?

Vocals: This is where compression really shines in live mixing. Vocalists can be unpredictable, and compression helps control big dynamic swings. For example, if your singer tends to go from a whisper to a scream, compression will tame the loud moments without affecting the quieter parts. I usually set the threshold so that the compressor kicks in only on the louder sections, with a 4:1 ratio to keep things under control.
Drums: Drums are tricky because of their wide dynamic range. Kick drums and snares especially benefit from compression, which adds punch while preventing them from overpowering the mix. I like to set a fast attack and release for drums to capture the initial hit and then let the natural sound come through.
Bass: Compression on bass helps maintain consistency in the low end, especially when you have a bassist who varies in playing style. A slower attack allows the initial attack of the note to come through, while a medium release keeps the sustain controlled.
Bus Compression: Applying compression to the entire mix bus can glue the mix together, smoothing out any rough edges between the instruments. Just be careful not to overdo it—too much compression can make your mix sound flat. I like to use a subtle 2:1 ratio on the mix bus, just enough to bring everything together without squashing dynamics.

Mistakes to Avoid When Using Compression

Over-compression: This is probably the most common mistake when starting out. Too much compression kills your dynamics, making your mix sound dull and lifeless. Always remember that less is more. Start with gentle settings and increase compression only when you need it.
Incorrect Attack and Release Times: Setting the attack and release incorrectly can either chop off the transients or make the compressor too slow to react. It’s important to listen carefully and adjust your settings to match the performance and room dynamics.
Forgetting Makeup Gain: When you compress, you’re reducing the overall volume of the signal. Don’t forget to add some makeup gain back to bring the level up so it sits correctly in the mix.
Using Compression in Isolation: Remember, compression is just one tool in your arsenal. Always check how it sounds in the context of the entire mix. A setting that works great on its own might not sit well once the band is playing at full volume.

What Are Some Practical Tips?

Start with Presets: Most digital consoles have compression presets for vocals, drums, guitars, etc. These are a great starting point and you can just tweak them as you see fit.
Use the Gain Reduction Meter: Watch the gain reduction meter to see how much compression is being applied. You don’t want it pegged at maximum reduction the entire time, that’s a sign you’re over-compressing the signal.
Stay Gentle: Don’t be afraid to use light compression! Sometimes just a touch of compression is all you need to tighten up the mix.

Compression is one of the most powerful tools in live sound mixing, but it’s also one of the hardest to master.

Hopefully, this has unpacked some of the basics and given you a solid starting point for experimenting with compression in your live mixes.

Remember, every room and performance are different, so take the time to dial in your settings and listen to how they work in context.

And don’t be afraid to trust your ears. After all, that’s what live sound is all about.

Keep mixing, keep experimenting, and compression will soon become second nature to you.