To many of us, the stereo bus compressor has become an important, if not indispensable tool in our mixing workflow. It’s almost as if we can’t truly “complete” a mix until we’ve applied the magic dust that our favorite comp seems to impart.
I am as guilty as any of sometimes relying on stereo bus compression as a crutch of sorts—though the benefits are undeniably real. My use (and love) of a good 2-mix compressor didn’t develop overnight, and in the beginning, it didn’t always seem to help in the way I expected it to.
Over time however, I realized that strapping a good compressor across the main mix provided a bit of sheen that I could not achieve by automating faders alone. It may not be “magic”, but it can be pretty damn cool.
Below, we’ll take a look at a range of some of the best and most popular options available today, to help you hear the differences for yourself and pick your own favorites.
What Makes for a Good Mix Bus Compressor?
The tricky thing about 2-mix compressors (as in with things audio) is that everyone has very specific and often idiosyncratic preferences. These preferences are formed as much by how each of us use the compressor and what kind of impact we expect the compressor to offer to the mix.
Many engineers think of a stereo bus compressor as something that forms a large part of the impact and aggressiveness of the mix, and will set the compressor accordingly, using as much as 4-6dB of gain reduction at all times. Others prefer to just use it for very gentle and transparent level control, while perhaps adding a bit of density to the mix. Both of these approaches are valid, and can yield results that are exciting and effective.
I tend to live in the “gentle and transparent” camp and have always had a hard time really digging way into a main mix compressor without feeling like something is being taken away from the mix. By contrast, I know people who use theirs more aggressively and would argue that hearing it working is the point of using it in the first place. To each his own, right?
Here’s a quick glance at all the compressors in the running. More on each in a moment:
“The Same, But Different”
When I set up this shootout, I had a clear process in mind and was pretty sure I knew what kind of result I would achieve. I have a bunch of 2-mix-worthy comps at my disposal and have used them all at one point or another with some success, so it knew it wouldn’t be hard to clearly show what each one does on the same piece of music.
I painstakingly set up each compressor as identically as possible, with regards to threshold, ratio, and attack and release times. I used a 400Hz tone to make sure they were all nearly identical in terms of gain reduction and output level. I had to ensure that my assessment was as objective as possible so that you could know that I wasn’t just trying to steer you toward what I prefer.
Once I had setup all 11 compressors to a very gentle setting (about 1dB of gain reduction) I was a bit surprised. When they’re barely working, the differences between them all were somewhat insignificant. There were definitely subtle variations in tone, but for the most part it wasn’t black and white, like “this one sounds the best”, or “this one will never work”.
It makes sense that the character of a compressor is defined largely by the sound of its gain reduction scheme and circuit, so naturally, the more you use it, the more it reveals. In essence, a shootout that doesn’t explore a compressor audibly compressing would be of little use to someone who wants to compare the differences between different models and types of compressor.
So, I modified my approach and came up with a better plan:
As an additional test, I figured it would be more useful to try the compressors on a few different types of music and then curate things a little bit by selecting only the ones that performed the best for that specific task.
This was meant to keep you from having to listen through all 11 different samples that are only subtly different while trying to maintain any perspective. It’s hard to hold that many sounds in your head at once, especially when the differences are minute, so that didn’t sound too productive to me. (But for those of you who want to really nerd out, I’ve also attached all the samples for download.)
While I would still test each compressor in the normal (for me), transparent manner, I also did my best to use the compressors in ways that are atypical of my approach, compressing the mix more aggressively. It was eye-opening (ear-opening?) to say the least!
In the end, all of the compressors I tested performed adequately—if not exceptionally—on all of the program material I tested with. But for brevity’s sake it made more sense to focus on the very best performers for each style of music.
I have quite a few of these “compressor” things at my disposal, and they represent a pretty good cross-section of what is most commonly used by professionals across many genres. All the major bases are pretty well covered here, including:
Manley Variable-Mu by Universal Audio – $299.00
This is an emulation of the famous all-tube compressor by Manley which employs the same gain-reduction method as a Fairchild 670.
It has a 1.5:1 ratio in “compress” mode and goes from 4:1 to 20:1 in limit mode, depending on the amount of gain reduction applied.
Elysia Alpha Master by Plugin Alliance (also available for UAD) – $299.00
This is an emulation of the Elysia mastering compressor, renowned for its ultra-high-quality Class A signal path and gain reduction circuit. It can operate in Feedback or Feed-Forward modes which makes it extremely versatile.
Brainworx Vertigo VSC-2 by Plugin Alliance – $299.00
This is an emulation of the Vertigo VSC-2 VCA based compressor.
It’s much like a classic SSL buss compressor with a couple more ratio settings and an all-discrete, mastering-grade signal path.
Chandler Limited Zener Limiter by Softube (also available for UAD) – $299.00
This is an emulation of the Chandler version of the Abbey Road/EMI limiters from the late 60’s and early 70’s, with a very colored, but musical, signal path.
The plugin version has been adapted and updated from the original designs to make it more versatile, consistently useful and modern.
Virtual Buss Compressors by Slate Digital – $149.00
This is a bundle of popular buss compressors offered by Slate Digital that includes three distinct models, each with a different tone:
The FG Red is modeled after the transparent Focusrite Red compressor, with a few added features. The FG Mu is modeled after the Fairchild 670 and adds some more versatility with fully variable attack and release times. The FG Grey is modeled after the classic SSL 4000 buss compressor.
Shadow Hills Mastering Compressor by Universal Audio – $299.00
This beast of a plugin is based on a beast of a hardware unit that carries the same name. It is comprised of an optical compressor and a VCA compressor in series.
In addition to these two stages of compression, it has three switchable output transformers—”Nickel”, “Iron” and “Steel”—and a built-in sidechain filter.
Fairchild Tube Limiter Collection by Universal Audio – $299.00
This emulation was an update of the already great Fairchild 670 from UAD.