The compressor in the sound module: How to use it properly! - Part 1

Get more out of your sound: Learn to master the compressor and create powerful kits!

You can achieve fantastic sounds with the compressor. Here you will learn step by step what you need to consider.

To distribute the drum sound in the stereo image, you utilize three dimensions:

  • Using the equalizer, you adjust the frequencies (Dimension Height)
  • You use the panorama control to position the signal to the left, center, or right (Dimension Width)
  • To create spatial sound, you have delay and reverb devices at your disposal (Dimension Depth).

That should cover everything, right?

In principle, by considering the three dimensions of the stereo image, you can indeed create a good mix in your e-drum module.

But just as with a car, the real driving pleasure comes from the extra features, and your drum sound can still be improved in various ways.

Depending on the equipment of your drum module, you will find effects from different categories, such as modulation effects (flanger, phaser, chorus) or distortion effects (overdrive, distortion).

It is highly likely that you will find a compressor. This belongs to the dynamic effects and can subtly stabilize, enhance, or transform your sound.

Since the compressor is a very versatile device, let's take a detailed look at how it can help you achieve more punch in your sound and make your drums sound cohesive.

What is the difference between Insert and Send/Return effects?

Effects can generally be classified into two groups: Insert effects and Send/Return effects.
The main difference between these groups lies in how they handle the signal you want to process.

Send/Return effects are applied where the processed signal is added to the original signal (dry signal).
This is the case, for example, with reverb. Imagine a choir in a church. When you stand close to the choir, you hear more of the dry signal from the singers than the reverberated signal from the church.

As you move further into the church, the sound gradually shifts towards the reverberated signal. Even when the dry signal is practically no longer audible at a certain distance, both components still contribute to the overall sound.

With Insert effects, it's different. The signal, such as the bass drum, goes into the Insert effect and comes out as the processed signal. This then becomes the "new" dry signal of the bass drum.

Insert effects are applied where the dry signal is replaced; Send/Return effects are used when the processed signal is added to the dry signal.

The compressor is a typical Insert effect. In the case of the bass drum, it can easily "beef up" the sound, making it more impactful.

Bonus knowledge: It is also referred to as effect routing, as you are generally free to place your effect wherever you want. This is particularly interesting for sound enthusiasts who like to experiment with unconventional methods. From this perspective, there is nothing wrong with using the Send/Return effect path for the compressor, for example. This technique is often used in practice nowadays to give the entire drum sound more impact.
All signals of the drum kit (bass drum, snare drum, toms, etc.) are mixed together and sent to an additional compressor. This compressor is set to extreme values and heavily compresses the sound.
If you then add this heavily compressed sound to the normal drum kit through the Send/Return effect path, even at a low level, the drum kit sounds much more powerful.
This technique is known among audio engineers as parallel compression or NYC compression (also NY compression). It is also commonly used in conjunction with the bass.

What does a compressor do?

As the name suggests, a compressor compresses the signal, i.e., it reduces the dynamic range of the signal. In simple terms, a compressor makes the loud parts of the signal quieter and the quiet parts louder.

However, this statement is not entirely accurate, as you will see.

Compression is important in the mix with other instruments to ensure that each instrument has a chance to stand out and is not overshadowed by other instruments.

It's not just about making the instrument in question louder!

The example of a symphony orchestra illustrates this. An orchestra consists of many instruments that provide a wide dynamic range. It can be very soft (harp, violins, flutes) but also extremely loud (timpani, brass, basses).

Imagine driving in a car and listening to an orchestral piece on the car radio. In classical music, the goal is to capture the sound as naturally as possible, preserving the large dynamic range.

As a result, the quiet passages will be drowned out by the noise of the moving car. So, you have to turn up the volume to hear the quiet passages.

Then, suddenly, a loud passage comes on, and the music literally blasts your ears, causing you to quickly turn the volume down.

If the quiet passages were slightly louder and the loud passages slightly quieter, you would have to adjust the volume control less frequently and with less intensity. Ideally, you would find a single pleasant volume level and keep it there.

Bonus knowledge: This ideal scenario results from reducing the dynamic range. The orchestra cannot be as quiet or as loud anymore.

As a result, the sound loses some of its naturalness. However, you will feel that the orchestra sounds louder and maybe even better.

There are two reasons for this. Firstly, a softly played instrument is not just quieter; it sounds different too! Our ears can perceive this very accurately, and they want to hear it that way!

So, the sound is just as important as the volume. Therefore, the effect of moderate compression of the dynamic range does not have a negative impact. The sound of the softly or loudly played instrument is still preserved.

The second reason is that the overall sound image appears louder, even though it is not.

It's comparable to a group of people comfortably spreading out in a room, and then more people enter the room, which is only half the size. The people have to come closer together. With the same number of people, the small room appears fuller because the people are closer together.

It's the same with instruments. With a reduced dynamic range, all instruments still need to find their place in terms of their volume, but suddenly they have less "room" to do so.

This is the actual effect of compression, which is the reduction of the dynamic range. The sound becomes thicker.

It appears louder, more impactful, and more present, which our ears generally perceive as better.

By the way, radio stations often use heavy compression for this reason. It ensures that the signal sounds loud even on small speakers and during car rides.

In fact, format radio stations tend to use excessive compression. You can test it yourself: turn on your car radio but keep the volume low. It can take your ears up to a minute to identify individual instruments in the compressed sound mix.

You should use such extreme settings with caution because they can also quickly fatigue your ears.

What are the different types of compressors?

Automatic Gain Control (AGC)

The simplest type of compressor is not adjustable. It is used in devices with Automatic Gain Control (AGC) in the recording path. AGC adjusts the recording sensitivity based on the volume of the incoming signal.

This type is not suitable for specific sound modifications.

Channel Compressor

This is the most commonly used compressor, often referred to as the "standard" compressor. With various controls, you can specifically manipulate and shape the sound. The range of adjustments can vary from subtle signal smoothing to extreme sound alteration.

You will most likely find the channel compressor in your drum module.

Bus Compressor

A bus compressor works similar to a channel compressor. Bus compression refers to compressing the entire mix (usually subtly) instead of an individual instrument. The compression of the bus signal "glues" the individual signals together, creating a more cohesive and unified overall sound.

Multiband Compressor

A multiband compressor consists of multiple compressor units, with each unit assigned to a specific frequency range. This allows for different treatment of the bass, midrange, and treble frequencies, providing more precise control over the dynamics of different frequency bands.

The multiband compressor is typically used on the master or bus signal rather than on individual instruments.


A limiter is a special type of compressor that provides an absolute ceiling for the signal's level, preventing it from exceeding a specified threshold. Unlike a compressor, which dynamically reduces the signal's level, a limiter sets a hard limit on the maximum level.

A limiter is often used as a safety measure to prevent signal distortion or clipping. It acts as a protective barrier against excessive peaks. That's why it's sometimes referred to as a "brickwall" limiter.

If set too aggressively, a limiter can also alter the sound or cause artifacts. "Driving the sound into the wall" is a common phrase used by audio engineers in this context.

What can I adjust on the compressor?

There are different versions of compressors available. The common models have up to four parameters that you can adjust.

With the Threshold control, you determine at what input level the compressor should start working. If the set threshold is not reached, the compressor remains inactive.

The Ratio control determines the ratio between the input level before compression and the output level after compression.

A ratio of 2:1 means that the signal enters the compressor with a certain level but comes out with half of that level. This applies only to the part of the signal that exceeds the threshold.

The Attack control allows you to set the time it takes for the compressor to engage after the threshold is exceeded.

Bonus Knowledge: A sound or tone starts with a transient phase that is louder than the actual tone. During this phase, there are the most changes within the developing sound. The part of the signal that undergoes the transient phase is called transient.

The Attack control gives you the ability to influence the transient. Since the transient is so characteristic of the sound, it is often undesired to have the compressor alter the transient.

Therefore, with the Attack control, you can set the compressor to start its action with a delay after the threshold is exceeded. The transient is somewhat "let through."

Release controls the time during which the compressor continues to act after the threshold has been undershot. Within this time, the normal ratio of 1:1 is restored.

There may be another adjustment called Make Up or Make Up Gain.

This is essentially a regular volume control placed after the compressor. It allows you to compensate for the volume loss caused by compression.

Even though the compressed signal may subjectively appear louder, it has actually become quieter.

Occasionally, there is also a Gain control. This is placed before the compressor to initially boost a potentially weak signal so that the compressor can work properly.

Continue to Part 2 here

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