By Donald Dinsmore
Why Would a Producer Compress Their Drums
You've probably heard all about the amazing things compression can do for your mix. Add punch, tame peaks, increase the average volume, impart tone, glue a sub-mix etc. But why do producers compress their drums and when should you do it? If you don't know what compression is I would recommend you go back to our last blog post, This is Your Mix on Compression, before you continue with this article.
Compressing drums is a tricky business. If done correctly you can add depth, weight, punch, tone, increase the RMS volume (see Part 1) of the track and glue the drum sub-mix together. If done poorly, compression will obliterate everything that was good about your drums to begin with by removing punch, weight, and groove.
When you look at the sound wave of any given drum hit, the sound can be broken down loosely into two parts. The first part of the sound wave is the initial hit of the drum. This high-amplitude short duration sound at the front of your waveform is responsible for the impact or punch of the drum hit. The transient also helps your brain determine how loud a certain is. The second distinct part of the drum hit is the tail, if you look at the wave this is the part of the drum hit that reduces in volume following the transient. The tail of the drum hit is a major contributor to the average volume (RMS) of the drum hit, how long it rings out and the rumble.
If you think back to our last blog post, I said that a compressor is like a little mix engineer in your DAW riding the fader and turning down the volume when the signal gets too loud. This why you can run into trouble when compressing your drums. If the attack on your compressor is too fast, you'll end up reducing the volume of the transient thereby sucking all the life, punch and high end out of your drums.
Often the goal of compressing drums is to preserve the transient and clamp down quickly on the tail of the drum hit. The result will be a spiky transient and an emphasized tail. That being said not every drum will benefit from compression. The source of the drum sound you're using should dictate the way you compress the drum (if at all). Typically, electronically synthesized drums don't benefit from the dynamic processing imparted by compression in the same way acoustically recorded hits do. However, electronic drums may benefit from compression in other ways. For example, by the addition of tone or an overall glueing effect from sub-mix compression. Another example is if your drum sounds are coming from commercial sample packs (i.e. Vengeance Sample Packs) they may already be heavily compressed, thus probably won't require compression.
Every time you reach for a compressor you should ask yourself, "What am I trying to achieve?" If you have a good reason to compress a sound, go for it. But if you're doing it out of habit, you should reconsider.
Compressing Individual Drums
When compressing your drums there are a few ways of going about it. In my workflow I often start with compressing individual drum sounds. There are a few things I might be trying to achieve when compressing individual hits. If I'm working with an acoustic drum hit the goal might be to have it cut through the mix better and increase the volume of the tail. If I'm working with electronic drums like 808s the goal will often be to add a certain tone or sound effect to the drum. Or maybe, I've layered a few sounds together to make a kick or snare drum sound. In this case, the goal will be to glue the sounds together so they perceived as one coherent hit and to sculpt the transient.
Compressing an Acoustic Kick
If I'm compressing an acoustic kick drum to help it to cut through the mix and emphasize the tail here are some of the settings I might use:
First thing I do is turn off the Makeup Gain, turn the attack all the way down, set the ratio to something reasonable like 4:1 and set a medium release time.
The next step is to bring the threshold down into the "way too much" territory. I'll adjust this later but it helps make the effect more audible and I find it easier to hear what I'm doing. Once you reduce the threshold you should be getting copious amounts of gain reduction. At this point, I'll set a ball park value for the release, I try to set it so that it is fast enough that the gain recovers before the next drum hits. Note: attack and release settings are time based parameter and as such they influence the groove and rhythm of your song, so the values you set for them will depend on the tempo of the track.
If you listen to the drum sound when the attack is ultra-fast, it will sound flabby and weak. To resolve this, fine tune the attack. Recall the goal is to allow the transient to peek through and then clamp down with the compressor. Start with an ultra-fast attack and begin increasing it. As you increase the attack time listen for the drum sound to change. Eventually you will start to hear the transient of the drum really smack. This is the sound you want. Keep increasing the attack until further increases in attack time don't influence the sound of the drum and then bring the attack back a little bit. If you look at your gain reduction meter you should find that the amount of gain reduction you're getting has decreased drastically.
At this point it may be worth while lowering the threshold so the effect is more noticeable. Now start playing with the release time. The goal is to compress (reduce the volume of the drum sound) immediately after the transient hits and have it recover quickly. If you set the release correctly you should start to get a snapping sound almost like a whip cracking. Now revise your threshold and ratio setting so you are getting a few dBs of gain reduction. In this example, somewhere between 3 and 5dB is plenty and gives a relatively transparent effect. For this application it can be okay to apply more gain reduction for a more compressed sound. Heavily compressed drums are a hallmark of certain genres like hip hop, dubstep and techno. Now increase your output gain so the level of the compressed signal matches the level of the uncompressed signal.
The final step is to determine if the compressed drum sounds "better" than the uncompressed drum. Sometimes it won't. If that's the case try revising the settings on your compressor or remove it altogether. I would recommend A/Bing the processed and unprocessed signal by bypassing the compressor while you listen to the solo'ed track. Then repeat the process while you listen to the effect in the context of your entire mix. You may find that sometimes this technique can hurt the low end of your kick. This can be resolved with EQ, add a low shelf boost and adjust the output gain so it matches the uncompressed signal and A/B again.
Compressing an Electronic Kick
Every compressor has its own sound. As you start to push different compressors you'll start to notice more than just the dynamics of a signal can be changed. When Ableton 9 Suite was released it came with a new compressor developed by Cytomic called Glue Compressor. It was modelled after "a famous 80's mixing console" and it imparts, in my opinion, lovely harmonics and warmth. In this example, we'll use the Glue Compressor to add some grit to an 808 kick from Ableton 808 Core Kit.
In this case the goal is really to be creative and abuse the sound using the compressor. Start by setting a ratio of 10:1, an attack of 30ms and the release to A (for auto). If the input gain is high enough you'll start to see a little red light labelled clip turn on in the upper righthand corner. Enable the button below it labelled 'Soft', this will give us more distortion. Really that's all there is to it. Feel free to play with the other parameters to dial the sound in to just the way you want it.
Using Compression to Glue Layered Snares Together
Layering drums is a fundamental part of sound design in many popular genres of electronic music. In a nutshell, the idea to have each layer contributing a certain characteristic to the sound. If you apply this to a snare drum, you would choose one sample that provides the low end smack, the next sample will provide the mid range (maybe a clap) and the final layer will fill in the high end (white noise or a snare with a really crisp top). Generally this technique involves shaping the envelopes and EQing the individual sounds to fit together before glueing them with a compressor. But for simplicity we will deal exclusively with the final compression step.
For this task I'll use Ableton's Glue Compressor. To start I'll set a gentle ratio of 2:1, the fastest attack (0.01ms), a release of 1.2ms and soft clip on. I'll bring the threshold down to so I'm getting around 10dB of gain reduction.
Just like in our first example, I'll start by increasing the attack while listening for the transient. In this case 30ms sounds good to me.
Now dial in the release. In this case I selected a release of 0.4ms.
The final step is to set the makeup gain. Because soft clip is enabled I can overdrive the makeup to add distortion, which also helps glue the sound, without exceeding -0.5dB. In this case, I adjusted it to 4.6dB. If you compare the uncompressed and the final compressed signal you'll notice that the compressed snares sound more cohesive and full.
Compressing a Drum Sub-Mix
The goal of compressing a drum sub-mix (or bus track) is a similar to compressing layered drum sound: gently raise the RMS volume, bring out some of the quieter elements of the drum mix and glue the drums sounds together so they sound like one kit. All that's needed in most cases is gentle compression. I think of this type of compression as the buttery smooth suspension of a luxury car. It should even out the bumps in the road for a nice gently ride but it won't be very responsive off the line or in the corners like a sports car. I'll use the Glue Compressor in this example to gently squeeze a hip hop beat.
I'll start with a ratio of 2:1, a fast attack (0.01ms) with the release set to Auto. I like the sound of the soft clip so I'll enable that too. Again, drag the threshold down to "way too much."
The first step, as always, is to dial in the attack. Start bringing it up. In this situation I still want the transients coming through so a slower attack is more desirable.
Adjust the release so it is a little more responsive (faster). You don't want to have it so fast you're getting that snappy sound so I generally try to set it so the gain recovers before the next major hit and it enhances the groove of the beat.
Next I'll adjust my threshold so I'm getting somewhere between 3 and 5dB of gain reduction. Finally adjust the makeup gain so it's the same volume as the uncompressed signal and A/B.
At the end of the day, compressing drums is all about what your specific goals are. A good rule of thumb if you want snappy, crisp sounding drums is a medium-slow attack time with a fast(ish) release. The reason being you want the transient of the drum hit to pass through the compressor largely unaffected. If the attack is too fast you will compress the life right out of the drums by reducing the volume of the transient. The release time is fast to allow an increase the volume of the tail. When the release is set too slow you will find the tail of the hit becomes quiet (room noise, the sustain) because the compressor will maintain the gain reduction through the tail of the hit.
I can't emphasize enough the importance of proper A/Bing of uncompressed and compressed drums. Make sure the makeup gain is disabled and set the output yourself so the level of the unprocessed and processed signals match. Once they match, you're in a positions to make a definitive decision when you A/B in the context of your entire mix. Sometimes it can be hard to scrap an effect after you spent 10-15 minutes tweaking it but be ruthlessly critical. If an effect doesn't help the entire mix, it doesn't belong in it.
Don't be afraid to experiment. After all, rules were made to be broken. Some of the best producers I've ever worked with break any and every mixing "rule" I've ever heard. Try ridiculous amounts of compression, try extreme ratios, low thresholds and odd attack and release times. Try a different compressor, put two compressors back to back with the same settings, put two compressors back to back with different settings, try putting a compressor in a different part of your effect chain. If it sounds right, it's right.
Next week we will investigate how to use compression on your bass sounds in Part III of our series This Is Your Mix on Compression.
More more information on compression and how to use it check out our Mixing and Mastering class taught by Tim Allan.
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