The Quest for Glue: Part 3

So I’m talking about mix glue in this series. When I last left off, I was theorizing about how analog can work to glue a mix together, however, we miss that if we’re working in the digital realm. Another way to get some of that glue can be through the use of a 2-buss compressor placed on the entire mix, but it’s important to understand that this isn’t the same as what we can get from analog. Our analog mix buss has a softer ceiling that isn’t always well-defined. You can almost think about it as running down a beach into the water where it gets harder and harder to run the deeper you get, and the deeper you get the more wet you get. The analog mix buss doesn’t work in a strictly linear fashion which can make it harder to get louder the more we push on the buss, and the harder we push on the buss the more distortion we get. Compression, on the other hand, is like picking a fight. A compressor pushes back.

So how does a 2 buss compressor work towards glueing a mix together? These are simply my theories, but I believe there are a couple things at work. For starters, we have the effect of the compressor. The compressor helps even out the level of the mix making it harder for things to jump out. The compressor pushes down on the mix based on the loudest parts of the mix. As a consequence of the compressors action, we perceive the elements within the rest of the mix as being farther down relative to the loudest which causes us to turn those up in response. So the compressor smooths out the signal level of our mix while forcing us to properly balance things. As the balance gets closer, the compressor continues to smooth over everything making the mix feel more cohesive or glued together.

When I’m using a compressor on my master buss, I don’t use a lot. We’re talking maybe 1-2 dB. It’s very subtle, and I’m really just tickling it. Some guys like to hit them a bit harder when mixing records, but I tend to stay away from this. In the studio, it is a lot easier to taylor a 2 buss compressor for each song, so you can be aggressive or subtle depending on what the song calls for. In the arena I’m mixing the band so I prefer something more subtle that will work on a broader scale.

There are varied opinions on when to add a 2 buss compressor into the mixing process in the studio. Some guys like to get their mix happening, and then throw on the compressor. Personally, I’m not a big fan of doing this because placing a compressor on the mix will affect and change the balance of things. I figure why should I spend a bunch of time mixing only to turn something on that makes me revisit my balancing decisions. Plus, live mixing is ongoing; the mixing isn’t over until the gig is over. I figure one way or the other I’m always going to be mixing into it.

I like to have the compressor turned on right from the start of mixing because I’d rather turn it off when it doesn’t work than add it in and revisit a lot of thing. I also find a couple of additional benefits to mixing into a compressor from the start: I use less compression on individual inputs, and I can put a mix together faster. The speed benefit here is really big for me because in live sound we are always up against time. It also means I don’t need to get bogged down working on individual inputs.

Of course, the big challenge in mixing into a compressor is how to set the thing up properly since it’s hard to anticipate how it’s going to react on an entire mix when that mix doesn’t even exist. You can turn it on and then constantly adjust it as you’re mixing, but it’s easy to start chasing your tail doing that since the compressor will affect your balance and your balance will affect the compressor.

The easiest way I’ve found to get a decent starting setting for my compressor is to use an old mix. Virtual soundcheck is very handy for this, but I can also use a board mix as long as there is no processing already on the mix. There are basically two goals I’m ultimately going after in this initial setup: a small amount of gain reduction and attack/release settings. Both of these things affect each other, but I kind of go after them separately and often use the ARRT method I discussed a few years ago.

I like to start by getting my attack and release time set based off the drums. While looping the loudest section of the loudest song, I’ll mute everything but the drums and slam the buss compressor so that I can really fine-tune the attack time. I like to set my attack so that the transients of the drums won’t have a large impact on the way the compressor reacts in order to have minimal impact on the transients of the drums within my mix. Some guys like to use a very fast attack time here to really compress everything, but it’s all personal preference. I then work on the release time to make sure the comp will release before the next drum hit, but sometimes this setting gets compromised a bit depending on the tempos of the songs in the set. Ultimately my release time probably ends up in the 200-300ms range, however, the attack setting seems to vary much more depending on the specific compressor I’m using.

Next I’ll work on getting a specific amount of gain reduction. This is hard for me because it goes against the principle of actually listening to the comp and setting it. However, setting this by ear is difficult because the existing mix is going to change when the comp gets added to it. Since I’m ultimately setting up the comp to mix INTO it, my experiences have shown that if I can get the unit to behave the way I want I’ll usually be OK when I actually put it into use. I personally like to use a pretty low ratio probably in the 2:1 or less range. Then I’ll bring up the entire mix and adjust the threshold so I’m compressing 1-2 dB in the loudest section of the song. Like I said, I’m going for subtle compression and should also mention that I typically prefer a compressor with a soft knee for this type of duty. I also like to use something with a sidechain filter so that I can make sure the compressor doesn’t respond to the bottom end of the mix and won’t be affected by the kick drum. The ultimate goal in all of this is to create the perception of glue, and it doesn’t take a lot of compression to do this.

Once I’ve got these settings, I write them down or store them as a preset. The next time I’m mixing I’ll start by turning on the compressor and loading my preset. As I mix I might make some slight adjustments to the compressor’s settings, but they are generally in the ball park. However, if things don’t feel right and I find myself trying to make a lot of tweaks on the comp, I’ll generally turn it off and try resetting it another day. This isn’t something I need to put together a mix, and so it’s not something I want to get hung up on getting right.

Now, there are some potential dangers and downsides to using a compressor on the master bus. Too much compression here can make the mix feel small and even fatiguing over time. Then there’s also the fact that this is compression which limits dynamic range. Dynamic range in live sound can really be amazing. Live sound is really one of the final frontiers for actual dynamics in music since record labels, mixers, A&R staff, and mastering engineers have systematically set about to destroy them over the last 15 years. Mix buss compression existed long before the current loudness wars ever began so this form of compression is not inherently bad, but I do believe restraint needs to be exercised with this technique.

As much as I’ve liked what a 2 buss compressor can do to a mix, I don’t use it all the time. If the band has decided to forgo dynamics and is already a wall of sound, the 2 buss comp can sometimes make things worse so I turn it off. It’s also important to me that there is some sense of dynamic change over the course of a set, and if it seems like everything is coming at me all the time the first thing I’ll do is turn off the compressor. Ed Cherney like to refer to a 2 buss comp as the engineer’s helper, but when it’s not helping I have no qualms about shutting it down.

I find that sometimes a good way to find out if it’s helping is to actually turn it off. If the mix completely falls apart without it, then that’s generally a good sign it’s working. If the mix gets better when I turn it off, I’ll leave it off. However, if I’m struggling with a messy mix and turning the comp off leaves the mix in that state, I’ll probably leave the comp off. Messy is hard to really define because it could mean things sound overcompressed or fatiguing or small or any number of other problems, but it’s basically the feeling that I’m fighting against everything. This could be the result of what’s coming off the stage or the comp settings being wrong, but either way I’m happy to turn off the comp and leave it off to rule it out.

In spite of the potential problems, I’ve still found using the 2-buss to be more helpful than not quite a bit when it comes to getting that perception of glue in the mix. I’ll also end this with one more little potential benefit that I’m hesitant to mention since it can lead to overuse, but it’s something that I think bears mentioning. Compressing your mix a little–seriously, just a little–can give the perception of a louder mix while maintaining a lower SPL level. I’ll leave it at that….