The following excerpt has been pulled in its entirety from Zen and the Art of Mixing:
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Stereo 2-Bus Compressor
If you’re mixing classical music, straight-ahead jazz, or any music that is best delivered with a dynamic worthy of only a dedicated listening room, a stereo 2-bus compressor is unwarranted. If you’re mixing any other popular genre of music, you need a stereo compressor, and you need a good one.
I’ve used the same stereo compressor on my 2-bus for nearly 20 years: the SSL G384, which is a one-space rack unit compressor modeled off the ones in the G series desks (although as of this writing I’m not able to determine how faithfully). When it comes to what goes on my 2-bus, I’m superstitious beyond the point of rationality. There are only a handful of compressors other than the G384 that I’d actually ever strap across my 2-bus, but I’d be hard-pressed to actually use any of them (hence my admission that I’m beyond the point of rational where this is concerned). If you’re about to go online to find the best price on a G384, you’d best make your way to eBay. Solid State Logic doesn’t make these particular compressors any longer—they now sell a “new and improved” version, and we all know what that means (HINT: It means it’s not as good as the original model). So, if you want the SSL G384, you’re going to have to purchase one used. I’m hopeful that this testimonial alone will raise the value of these compressors. As it is, I can already sell mine for more than I purchased it. Not that it matters. I wouldn’t sell it—not even from my deathbed.
Your stereo bus compressor is the one compressor that you would be ill-advised to use in the plug-in form. This might be reasonable on a temporary basis as you learn (and earn!), but analog compressors are far better than their digital counterparts for the job. This is especially so when you directly compare the plug-in to the analog compressor it emulates. You can perform about 80 percent of the heavy lifting where compression is concerned with a hardware 2-bus compressor, but it’d better be pretty damn stellar at the job. If you get the impression that I freak out about everything and anything that goes on the 2-bus, you’re right; and there’s a good reason for this. The 2-bus affects the entire mix!
The Internet is a great place to get bad advice where your stereo compressor is concerned. The number-one myth is the notion that stereo compression should be left in the hands of the mastering engineer. While there’s no doubt that mixing with a stereo compressor takes practice, and while it’s quite possible that you’ll fuck up several mixes in the process (can you say overcompression?), it’s essential that you as the mixer—and only you—compress your mix.
Most mixes of popular music will need compression, particularly if you want the mix to work anywhere outside of an isolated listening room. As has been pointed out repeatedly, a dynamic range of anything more than 4 dB is unrealistic for the habits of today’s music buyer. A wider range might have been acceptable 30 years ago, but today people tend to listen to music as they engage in other activities. This means that music must compete with external noise, and if the dynamic range is too great, sections will all but disappear from audibility in any real-world situation. Most music must compete with noise from cars, dishwashers, dryers, babies crying, hairdryers, etc.
So why not leave compression up to the mastering engineer? Simple: your balances will change far too drastically for this to be a reasonable option. Balance is your main weapon for manipulating the listener’s emotions and focus. If you’re going to spend hours upon hours getting those balance relationships just right, why would you find it acceptable for them to completely change come mastering time? If you don’t compress the stereo bus while you mix, you’re not delivering a mix. You’re delivering some weird approximation of a mix, and it’s not even that, since you can’t predict precisely how the mix is going to change—and it will change.
One could certainly argue that EQ done by the mastering engineer will change balances, and although that’s technically true, EQ adjustments work relatively uniformly across your mix. Your mix won’t suffer from some minor EQ adjustments, and if it requires major EQ adjustments, then the mix was broken to begin with. Frankly, I take great offense when a mastering engineer puts a compressor on my mix.
You can certainly mix without an analog stereo compressor, and if your monitoring and summing have left your bank account depleted, this coveted addition to your mix arsenal can wait. But this will put you in the unenviable position of having to do all of your compression on the individual channels, which is time-consuming and nowhere near as effective as a stereo compressor on the 2-bus. One high-quality analog stereo compressor can make your life so much easier and mixing so much faster that the time you ultimately save (once you get past the learning curve) will pay for the unit in just a few projects.
Stereo 2-bus compression is like adding glue. Whether you choose to use it aggressively as I do, to reduce the amount of individual channel compression necessary, or whether you prefer a more subtle approach, it’s an invaluable tool for mixing.
In general, you should strap your 2-bus compressor onto the mix right from the start. But if you really want to get an idea of the power of a 2-bus compressor, take a moment to get your bass and drums mixed, and then strap on the compressor. The control it will supply over the bottom of your mix will be obvious, and you may never take it off your 2-bus again. I have mine strapped across the 2-bus even while I’m recording.
Most stereo compressors have a sweet spot. If you hit the compressor too hard, your mix will become too compacted and your low end will be neutered. Both of these symptoms will actually make mixing more difficult. If you hit the compressor too lightly, you won’t get the gluing benefit, and your bottom end will be inconsistent at best. I’ll warn you now: mixing with a compressor strapped to your 2-bus can be nothing short of frustrating, and can give you a whole new appreciation for the overall tail-chasing experience that is mixing. Even after you get past the learning curve, you’ll still find yourself adjusting the threshold when the mix is getting close. Reducing or increasing the threshold of your 2-bus compressor at any time during the mix, even by the tiniest margin, will completely change your internal balances and overall EQ curve. That said, a threshold adjustment can also be the one change that brings your mix into perfect focus.
The ratio you use on your stereo compressor is up to you. I typically use a 4:1 ratio, as I find 10:1 far too aggressive for the 2-bus. Pick whatever ratio works best for you. Your attack and release settings really have more to do with the program than anything else. These should be set purely by ear. When you hit upon the best attack/release settings for the track, your mix will immediately start to sing, so avoid getting into the rut of using one setting for everything that you mix. Once you’ve figured out the best settings for your mix, don’t change it! Otherwise I fear you’ll be cursing me until the day you retire for having convinced you to strap a compressor onto the 2-bus. We wouldn’t want that to happen.
There’s one other way to gel your mix, and that’s by slamming your 2-bus with your mix. This method allows the electronics on your 2-bus to act like a limiter. If you’re mixing in the box, this isn’t an option. You have to have an analog 2-bus to do this. Furthermore, not all 2-buses are created equal. The 2-bus on an SSL will crumble in short order, yet you can absolutely hammer the 2-bus on most of the 80 series Neve desks to the point that the meters are pinning at all times as you work. If you find yourself on a vintage console, try it, and see how far you can push it. You might find it makes your life easier.
Zen and the Art of Mixing is the first book in my ongoing Zen and the Art of series. The digital versions (Kindle, eBook) contain loads of supplemental videos. You can purchase any and all of these books HERE.
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