Here’s the thing about compressors: they’re not always used for what you think they’re for! And, how you think about using them fully determines the results you’ll get from them. Most people are taught, or assume, that compressors are for controlling the level of a sound. In fact, that is why they were invented, as “auto-leveling amplifiers,” but we’ve gone way past that application now, and frankly, track automation is probably better for that anyway.
Compressors are really used to change the tone, or the waveform of the signal. So, you see that this is not about level but rather about the way in instrument or vocal sounds in the track.
The quintessential compressor has 4 knobs: Threshold, Ratio, Attack and Release. There are many variations on this, but they’re essentially the same. In fact, there are so many variations that I had trouble finding a good example. However, the stereotypical version, like the revered Avalon pictured in Figure 1, has 2 large knobs, Threshold and Ratio, and two smaller knobs, Attack and Release.
A classic plug-in like the Waves Renaissance Compressor, while using sliders, essentially draws your eye to the two big sliders in the center, Threshold and Ratio, while the Attack and Release are on smaller sliders at the bottom.
Notice that the layout tends to reinforce that the key controls are the Threshold and Ratio. In fact, those may well be the first controls that you need, but are not the ones that require your greatest attention. Once you have the Threshold and Ratio set you can practically forget about them. Where the magic really happens is when you start to adjust the Attack and Release.
The tonal shaping abilities of your compressor are best understood using an example. Let us consider snare drum: any drum hit consists of a very rapid transient, that is made by the stick hitting the drumhead, followed by a decaying tail that is the energy being transferred to the shell of the drum and the shell vibrating in a damped fashion. The interesting thing is that the very fast transient is so fast that our ear doesn’t really hear it. However when our playback system is set to play such a large burst of energy without distorting, the tail or body of the drum hit seems very quiet by comparison. To make the drum seem louder, or more importantly, more present, we need to change the relationship between the height of that transient and the body. We do this by adjusting the attack and release.
By adjusting the attack to a very fast setting we are able to apply the compression to that early large transient. Then by adjusting the release to something that is also very quick we prevent the compression from being applied to the body. Now we’ve changed the relationship between the transient and the body of the hit, functionally making the body louder and changing the tone to emphasize the body characteristics of that drum.
We could, of course, apply the same scenario in reverse. If we have a dull and lifeless snare because it has no pop, we could apply the same compression but with a slow attack and the slow release to emphasize that initial transient. The fun, or the art, is in finding that sweet spot for both attack and release that balances the crack of the stick hit with the tone of the body.
Bass guitar is another instrument where this trick is handy. Most often the bass feels a bit choppy if the bassist isn’t really attuned to his or her dynamics. By applying compression with a medium attack to just let the finger or pick attack through, and then a medium release to contain some of the growl, but allow the distant tail to remain uncompressed, we can even out the note and give the track a fuller, more consistent feel.
Vocals often need compression, and often fairly complex compression. Remember that different compressors will differ in how well they handle certain sounds, and that compressing really hard with one compressor is usually not as effective as two machines working less hard. In pop music, often the vocal is compressed to hell. Typically, this means one compressor to shape the tone as we’ve discussed, for example an Avalon could be used with light compression, medium attack and medium release to even out and thicken the performance, followed by a more brutal assault, say with an LA-2A, to gel the track and get that “in your face” sound we’ve become so used to. (Notice that the LA-2A doesn’t have Attack and Release settings at all, but uses the input knob to drive the circuit, creating the reduction, and the attack and release vary with the level of input and the amount of reduction).
Now that you know, forget about those Threshold and Ratio knobs: set them to get the machine working, but then dial in the tone with your Attack and Release. This is the stuff that makes tracks go from demo to hit!
Now that you know, forget about those Threshold and Ratio knobs: set them to get the machine working, but then dial in the tone with your Attack and Release. This is the stuff that makes tracks go from demo to hit!
BONUS REVIEW BELOW!
by Chris Devine
Below, check out a review of one of our favorite (recent-ish) hardware-based compressors that you can add to any home studio setup easily and affordably, the Warm Audio BUS-COMP VCA Console-style bus compressor.
Warm Audio is one of our absolute faves when it comes to awesome studio gear on a budget. One of the things we’ve been bugging them about for a few years is a stereo bus compressor, and now that we’ve got our hands on the new BUS-COMP, it’s just what we’ve asked for.
We have a modest recording rig here at the mag that we use for testing, but as of late we’ve been doing compression only in the box with a few stock plug-ins. While the sound was fine for demo’ing and testing out products, we knew that for really great sound, we’d want to look into an insertable hardware unit at the end of our master chain.
The new BUS-COMP delivers on everything we wanted, including price. For just under $800, you’ve got a two channel VCA bus compressor that just adds that little extra glue to the end of a mixing session. It’s hard to stress just what a compressor can add to your mix, but A/B testing some scratch sessions with and without the bus compressor confirms that the dynamic gel you hear on radio-ready singles is just the thing this puppy can bring to your rig.
One of the cool things is you can run your mix through this and just use it for slight tone coloration on its own, with no compression settings applied. But of course the magic really kicks in when you start running your stereo sources through it (of course it can be used on single-channel sources, as well). And, it should go without saying, but you don’t just have to use it on your stereo master, you can sweeten background vocals, rhythm section mixes, drum mixes, etc, too from your stems.
Getting into the settings, it comes equipped with exactly what you’d expect and want on the front panel, including knobs for threshold, attack, ratio, release, a high-pass filter and make-up to adjust the gain back you may have lost in previous settings.
The HPF has settings for 30, 60, 105, 125 and 185 Hz and you can do what we did and quickly A/B your sound with and without compression with a button on the front panel. While built to meet a certain price point, for sure, Warm didn’t skimp on quality, which we appreciate. They used Made in the USA CineMag transformers and fully discrete op-amps inside, and the internal guts of neatly wired and. Laid out for easy servicing in the future. There’s also some room inside the chassis for the modders in the crowd.
Turning around to the rear panel, and I/O is dead-simple. Left inputs and outputs and a side-chain input are all that’s needed, and all that’s here. That makes integration into your rig simple and eliminates confusion for newbies.
Overall, the new bus compressor from Warm Audio is an awesome and affordable way to finish off your stereo mixes, or even stereo stems, and we heartily recommend it for any home or pro studio.
PROS:
great sound, easy to install and use.
CONS:
none.
STREET PRICE:
$799