We’ve come to count bus compression among the essential mixing techniques. It’s common to the extent you can’t imagine a studio life where it didn’t exist.
But it very well didn’t until the early 1980s! This is when Solid State Logic (SSL) in Oxfordshire, England, built a large-format console with dynamics processing on each channel, including the master bus. We can only guess whether it was a deliberate move, or one for completeness’s sake. Regardless, it changed the rules of mixing (and, consequently, the sound of records) forever. Before the SSL G-series console made its way to recording facilities, it didn’t really occur to most audio engineers to compress the entire mix prior to mastering. Once they tried it, literally because they could, mixes wouldn’t leave the studio without a drop of the fabled ‘mix glue’.
The Bus Compressor is famous among studio diehards for this and other overwhelmingly positive reasons. It’s been a while since the SSL 4000 G mix consoles were top of the range. But the bus comp remains there, in mostly original form. The approachable, no-nonsense engineering behind it (very typical of SSL) did turn it into a template for countless clones and spin-offs. But the OG design is a rare instance of a manufacturer of highly specialized and sophisticated equipment getting something 100% right from the get-go. The only hardship with the bus comp is the overwhelming desire to overdo it! Luckily, ripping it out of a vintage console the size of a room isn’t one. SSL caved in to demand, made the 4K bus comp into a rack unit, and let it take a life of its own. When plug-ins became viable means of emulating analog gear, it was among the first studio classics to get a digital reincarnate.
The SSL bus compressor is also renowned for its ability to bring instruments in a mix together in just the right ways. Clean and tight performances, recorded close mic’d (or direct) and mixed competently, may sound overly distinct. In that case, the parts are competing for your attention on their own, instead of uniting to get across what really matters – the song. By subtly squashing their dynamic range, the bus comp ‘glues’ them to each other, but the definition stays. Truthfully, any decent compressor on a bus can pleasantly tighten up a mix, but nothing feels as on-point as the SSL Bus Comp (or a unit made in its spirit) does. While we’re talking complete mixes up till now, the Bus Comp can work pretty much any bus group – especially drums! Nothing beats the 1176 ‘all-buttons-in’ for total obliteration, but the Bus Comp comfortably gets any ol’ drum kit to kick up a fuss in no time.
It only helps that the SSL bus compressor’s faceplate is so clear and to the point. From left to right, these are the essentials you’ll find:
VU Meter – Indicates the amount of compression as gain reduction
Threshold – Adjusts the signal threshold where compression kicks in.
Attack – Adjusts the compressor attack. Slower speeds let more transients through, the compression is perceived as subtle and performances punch through. For faster speeds, the opposite applies.
Release – If you don’t dial it in correctly, the mix kind of sags and loses momentum. You probably don’t want that, but tweak to taste!
Ratio – Adjust the ratio between clean and compressed signal. The higher the ratio, the heavier you’re slamming audio.
Make-up – Lets you dial in the volume lost from gain reduction back to where it was before compression.
For the Synergy Core take on the venerable bus compressor, Antelope Audio modeled the unit from a genuine early 4K board. Included is a sidechain filter knob that lets you prevent unwanted frequencies from influencing the compressor’s behavior (40hz boom and thunder, lookin’ at you!). If their COMP-4K-BUS effect were to exist in hardware form, it would make for a genuine, but meaningfully modernised unit. The COMP-4K-BUS is truly an appropriate treatment for such a classic piece of gear that’s earned its legendary status through sheer prowess.
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The classics: This SSL-made Bus Compressor is an everlasting source of ‘mix glue’