How do compressors add note definition?

[mjcarp79]

I am fairly new to using compression, and I am puzzled by something: I notice that using even light compression adds definition to the "leading edges" of notes. (The notes sound like they start more abruptly, giving a "crisp" kind of feel to them.) As the level of compression increases, the effect becomes more noticeable. When I get into very heavy compression, it actually seems the the notes have a "snap" or "pop" to the leading edge.

Now, I like this effect, but my understanding of compression must be faulty, because I don't understand why/how my compressor does this. I have a Keeley Bassist, by the way.

I would appreciate some insight into this, from those who understand compression better than I do. Thanks!

 

[nmiller]

If your compressor has variable attack, I suggest trying different settings on it. A slower attack means that lower frequencies have a chance to sound before the compressor kicks in; at the right settings, this means that a bit of low-end thump can be heard before the volume is squashed. When mixing a recording, I typically use a 3-5ms attack on vocals and guitar, but at least 15ms on bass for this reason. That extra bit of thump can register as note definition, so if you play the same note several times in a row, each one comes through with clarity.

 

[Mushroo]

I agree with @nmiller that the relevant variable is the "Attack" knob.

The longer your attack time, the more of the initial transient gets through, before the compressor clamps down.

The end result of using a slower attack time plus higher compression ratio, is that your playing has more dynamic range (not less dynamic range). Everything gets compressed or squished except the initial peak or transient. That's why they call it the "attack" knob!

It's easy to see this visually in your DAW software if you do any home recording. As you sweep the Attack knob, you will see the waveform get more "peaky."

There is an urban myth that compressors rob your playing of its dynamics. That's only true if you are still learning how to work the knobs. Compressors are a tool for shaping dynamics, not a weapon for destroying dynamics.

(Edit) I see that the Keely Bassist doesn't actually have an Attack knob? It's preset from the factory? So I think you just got lucky, and the folks at the Keely factory happen to have similar tastes to your own ear. They chose a "sane default" setting for the attack time, that just so happens to work well for your needs.

 

[jblock]

I’m a fan of the Keeley. Does this happen even at a low ratio like 2:1? The Keeley Bassist handles attack/release automatically based on your playing so that can seem like it’s clamping down as you’re digging in. Turning down Threshold will mean the compressor engages less so that’s worth a try if you want more transparency.​

 

[Mushroo]

Here are the waveforms from 5 different compressor pedals (the first one is the uneffected "dry" signal). I used a looper pedal to feed them identical input, so any variation in the waveforms, is completely due to the compressor (and not my sloppy playing). As you can see, all 5 compressors have very different waveforms. Some are more "peaky" than others. This is due to many different variables, but two of the biggest variables, are the attack time and the release time.

Can you see, visually, that some of the compressors actually increased the dynamic range between the initial attack transient vs. the sustain of the note's dynamic envelope?

 

[sears]

@Mushroo whoa, that's great! I'm guessing the last one and 3rd to last are optical because they have that first priming note. All but the second compressed signal look like they compress the peaks one lobe (?) more than the other.

 

[Mushroo]

@Mushroo whoa, that's great! I'm guessing the last one and 3rd to last are optical because they have that first priming note. All but the second compressed signal look like they compress the peaks one lobe (?) more than the other.

You're good! Yes, those two are optical compressors.

From left to right: dry, Accountant, Cali76 CB, Monocomp, LAB, PDRV.

My personal favorites from this shootout were the Cali76CB and the LAB. They sounded the "loudest" to my ear, and I think you can see that visually in the waveform. (All of the tracks are normalized.)

 

[Killing Floor]

Compression affects your attack but also the sustain because it can level up notes that are played softly. It’s give and take. That’s primarily how I use it, evening the notes.

 

[mjcarp79]

Can you see, visually, that some of the compressors actually increased the dynamic range between the initial attack transient vs. the sustain of the note's dynamic envelope?

Yes, that is interesting. I am not accustomed to looking at waveforms like that, but what I think I am seeing seems to correlate with what I was describing.

 

[Cave Puppy]

It's the attack as others have said. The time the compressor takes to kick in. There are several excellent videos on youtube (where else?) about this subject. A studio hardware or plug-in (software) compressor works identically to a pedal type of compressor so almost any video about how studio/plug-in/any compressor works should explain it. A lot of pedal compressors don't have all the controls a plug-in or a hardware compressor may have so keep that in mind.

 

[Fuzzbass]

I am fairly new to using compression, and I am puzzled by something: I notice that using even light compression adds definition to the "leading edges" of notes. (The notes sound like they start more abruptly, giving a "crisp" kind of feel to them.) As the level of compression increases, the effect becomes more noticeable. When I get into very heavy compression, it actually seems the the notes have a "snap" or "pop" to the leading edge.

Now, I like this effect, but my understanding of compression must be faulty, because I don't understand why/how my compressor does this. I have a Keeley Bassist, by the way.

I would appreciate some insight into this, from those who understand compression better than I do. Thanks!

Curiosity is a wonderful thing. I'll just say that misunderstanding/misinformation about compression is still pervasive, and leave it at that. Excellent question, and cheers to you for having an open mind.

 

[yakmastermax]

It isn't just attack, but attack is definitely one of the main controls that contribute to the sound that you're describing. I love the sound of "pumped" compression. Longer attack times, short release times, high ratios and low thresholds will result in this sort of pumping sound.

 

[40Hz]

I see that the Keely Bassist doesn't actually have an Attack knob? It's preset from the factory? So I think you just got lucky, and the folks at the Keely factory happen to have similar tastes to your own ear. They chose a "sane default" setting for the attack time, that just so happens to work well for your needs.

It’s not so much a preset as it’s automated.

The way the Keeley Bassist handles attack and release. (source: Keeley Engineering Bassist and GC-2 Limiting Amplifier Owners Manual)

Attack and Release:This pedal has no attack and release controls.There is a reason for this.There is a certain figure that just sounds good as far as compression goes; and that’s 125 dB/ second. With feed forward compressors that use this type of true-RMS detector you use a single time constant parameter. The timing capacitor gives you attack and release times that are adaptive to your playing level or the signal input to the compressor. Bottom line:Attack and Release times vary on program content. Attack times are generally speaking, about 100 times faster than release times. Attack Time: typically 15ms for 10dB, 5ms for 20dB, 3ms for 30dB Release Time: typically 8ms for 1dB, 40ms for 5dB, 80ms for 10dB, 160ms for 20dB, 240ms for 30dB​

 

[makanudo]

They don't 'add' anything. They prevent your signal from going over a set point or attenuate it once it does by a set amount.

So when you slam on a G on the E string and you pluck the G on the D string during a groove, the gain from the more powerful low G is reduced by x amount and remains relatively even to the high G gain which if it crosses the threshold also get's attenuated and thus, keeps things more even. More 'defined'.

Usually the low end of your spectrum will hit the threshold first because it carries the most energy relative to the rest of frequencies. So it will get compressed first/most and keep your signal more even and thus avoiding the bass/mud frequencies from becoming a muddy undefined mess.