The Balancing Act – Parallel Subgroup Compression

I remember back when I first started figuring things out in my club days. I only had 2 compressors and 4 gates on my Foh rack. There was always something that needed a compressor more than the drum channels. Whether it was vocals, keys, or bass, they always needed it more. So I fell in love with the crispness of uncompressed drums, when tuned well and played with dynamics. There’s a visceral impact to a live drum kit that makes them a joy to listen to. The emotion that drives our primal desires is prodded by the attack and decay of a resonate object struck by hand or stick. Drums are cool. But I digress – back to my lonely compressors. Since this was pre-internet, most of my knowledge was gained from industry mags and watching other engineers. Everyone talked about how cool their “comp” was. And the meters looked rad. What’s not to like about a little dynamic control? I started collecting compressors and amassed 8 or 10 channels in no time. I put them on everything, including kick and snare, and slowly began sucking the life out of my drums. I mean, they sounded ok, right? Mesmerized by the flashing lights, I fell down the gain reduction rabbit hole. I liked the added energy and slower decay of compressed drums. Between the comp and gate, the attack and decay of the drum could be contoured to what I wanted… mostly. It took a while to figure out how attack and release worked. But I was in control and my drums sat in the mix. Fast forward to the widespread introduction of digital consoles – suddenly every channel had a compressor. More recently, you can get compressor “plugins”. Put vintage tube compressors on everything. Sometimes two or three. They’re cheap!

I spent a few years working for a percussionist who had a lot of drums. One tour we had 37 channels coming from the percussion riser. Compressors and gates were necessary to keep this chaotic landscape listenable. But I began to grow dissatisfied with the way compressors were affecting my “drum kit” mix. Between club gigs and festivals, I was mixing many different bands, most with decent drummers, so I refined my drum sounds constantly.  It was easy to experiment with different techniques and compare/contrast between them.

One day, I was reading an old copy of TapeOp and there was an article about this technique called “Parallel Subgroup Compression”. I had never heard of such a thing. The article described how you set up the drum channels without inserting individual channel compressors. Instead use one stereo compressor inserted on a pair of subgroups, using it to compress the whole kit (or just the channels you assign), then mixing that in with the uncompressed drums. The technique made sense. It sounded like the best of both worlds. I tried it and loved the results: the snap and pop of a well tuned snare but with a sustained decay from the subgroup compressor.

After a few gigs I worked out a system something like this:

I usually start with the subgroup fader all they way down. Route the drum channels to the Main Bus (Left-Right, ST, whatever it’s labeled) AND to a stereo subgroup, then route that subgroup to the Main Bus. Insert a stereo compressor on the “drum” subgroup. Build a good drum mix on the Main Bus without compression. Since they’re also routed to the drum subgroup, I should start seeing metering on the compressor. Set the subgroup compressor aggressively, with short attack and medium/slow release times. I really squeeze that subgroup. I find that a 6:1 ratio resulting in 10-12dB of gain reduction, with the drummer playing hard, is a good starting point. As I raise the subgroup fader, I’m adding the extra RMS energy and harmonic density of the compressed drums to the crisp transients of uncompressed drums. It does require a well tuned drum kit, but the results are exciting. Especially with the ability to change the overall amount of compression on the drum subgroup with one set of controls and the subgroup fader level. I find that this configuration sounds great and provides flexibility in tone and dynamics. It allows the drum kit, which has a low RMS energy acoustically, to compete in a mix filled with guitars and keys, which can have a higher RMS energy. Your mileage may vary.


5 Comments Add yours

  1. Savanna says:

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