How Do In-Ear Monitors Work

In-ear monitors for drummers help musicians to hear the music while playing during a performance. Today, most types of in-ear monitors [In-Ear Monitor Types] are wireless.

Below, we’ll talk more about how in-ear monitors work and how to use them.

How In-Earn Monitors Work

In order to fully understand how an in-ear monitor works, let’s cover the basics of this device first.

You can think of in-ear monitors (or IEMs for short) as professional-grade counterparts of wireless or wired earphones. IEMs are commonly used by audio engineers, audiophiles, and musicians. They’re inserted into both ears to physically block out external noises and clearly hear the music you’re playing, without the need for wedges.

Why do drummers (or other musicians) use in-ear monitors [Why Do Drummers Wear In-Ear Monitors]?

  • Give musicians more freedom to move around, although this isn’t really necessary for drummers
  • Protect them from hearing damage and long-term ringing in the ears due to the extremely loud on-stage sound levels
  • Lessen the work of audio engineers because they don’t need to frequently turn up the volume on the system
  • Reduce drum noise to a safe level
  • Block high-frequency sounds and other undesirable stage noise to allow drummers to always hear what they’re playing (except for hearing the bass drum)
  • Produce a highly clear mix if they work with a skilled monitor engineer

There are three components of a complete in-earn monitor system:


A transmitter is a half-rack unit that’s connected to a mixing console, which merges or mixes sound signals from various sources. It’s usually placed off to one side where it can transfer the audio or monitor mix to a wireless receiver pack (worn as a belt pack) through a system of radio signals (meaning, wirelessly).

Every single mix will need its own transmitter. So, if you’re part of a band, you can use more than one transmitter to designate each mix to each member. However, if your band members are fine with sharing the same mix, one transmitter with many wireless receiver packs is enough for the job.


The receiver of an in-ear monitor is normally worn like a belt bag. The device, which is about the same size of a mobile phone, is where the earphones are plugged in. It also has a knob for correcting the volume playback level of the input sources.

The main job of the receiver is to pick up the monitor signal from the transmitter. Then, it sends the amplified sounds to your ears through a pair of earphones.

Multiple receivers can connect to a single transmitter and get the same mix or audio program. Think of it this way: It’s like 100 people in their cars listening to the same music on their radios.

However, the transmitter and receiver(s) should operate in the same frequency, which is usually between 606 and 614 MHz (megahertz). There are other UHF bands other than what we just mentioned, but they might require a special license.

In the United States, two agencies are responsible for regulating radio frequency or radio spectrum:

  • The Federal Communications Commission (FCC)
  • The National Telecommunications and Information Administration (NTIA)

Different brands of in-ear monitor systems, such as Shure, Sennheiser, and Audio-Technica, provide different operation modes. For instance, the Shure PSM in-ear monitor systems have three modes of operation:


In this mode, the mixing engineer would produce a stereo mix that’s fed to the transmitter. From there, the stereo mix goes to your receiver and you’re able to listen to the mixes in each earphone. If you like the ability to pan different elements in each ear (e.g., drums and vocals), you’ll like this mode.

IEMs with stereo transmitter/receiver tend to be more expensive, but the difference is significant. Compared to mono mode, the stereo mode gives you the ability to clearly hear all of your band mates and at a lower volume. It helps you become more aware of the space around you while performing.


Not everyone is a fan of the mono mode, but it’s still one of the widely used formats. With the mono (meaning, one or single) mode, a single channel audio is fed to one channel to play the recorded sounds. To put it simply, you’ll hear the same mono audio file in your left and right earpieces.

Mono isn’t necessarily inferior to stereo. You can have your sounds in stereo, while the rest of the bad in mono or stereo. Depending on the venue, stereo may sometimes cause phase cancellation issues, which can lead to the production of a hollow and weird sound.

Possible reasons for using the mono mode instead of the stereo mode:

  • You already own a mono system
  • You don’t want to shell out money for a more expensive stereo wireless IEM system
  • You don’t want to expand to more channels (since stereo sources require more channels)
  • Your group is already running mono for front house of house (FOH)


Mix mode is probably the most useful mixing mode because it gives you greater control and flexibility. You can control the volume, operation mode on the receiver (for instance, listen to the mix in mono mode), and balance between every channel. In addition, you can adjust your own mix while on stage.

Let’s say you send two inputs to the transmitter. Let’s call them Input E and Input Z. In Mix Mode, you can choose to hear Input E or Input Z in your left and right ears by making changes to your PSM receiver. For instance: Input E is a mix of all of the other instruments; Input Z is a click track only.

Note: You can choose whatever inputs you prefer and make adjustments, which don’t really affect the other musicians on stage who are also using Mix Mode.


The earphones of in-ear monitors are smaller because they have to fit comfortably in your ear to create a tighter seal, while still reproducing low frequencies with accuracy. Compared to consumer earphones or headphones, in-ear monitors have smaller drivers (usually three or more) to create their sound quality.

The quality of the sound will depend on every component in your in-ear monitor system. Even if you use a good-quality transmitter, using generic earphones will prevent you from hearing the entire frequency spectrum. On the other hand, using a low-quality wireless system will still limit the capacity of any top-notch in-ear earphones.

If you’ve never used in-ear monitors before, it’s important to know that you might feel uncomfortable the first time you wear them. One major reason is the background noise, including the noise from the audience and your band mates, completely disappears.

Solution: Some manufacturers solved this issue by producing earpieces that are capable of mixing ambient sound with the monitor mix. Sensaphonics’ IEM system with 3D Active Ambient™ IEM technology, which embeds MEMS microphones, accurately picks up room sounds and allows you to add those sounds to the monitor mix.

Here’s How In-Ear Monitors Work

The concept behind how in-ear monitors work can be confusing at times. We’ll try our best to explain it below.

Step 1:

You could probably liken a wireless in-ear monitor system to playing music that’s saved on your mobile electronic device (e.g., tablet and phone) or computer using a Bluetooth-capable speaker. Your mobile device acts as the transmitter, while the Bluetooth-capable speaker is the receiver.

In-ear monitors also operate using wireless technology. But before going to the transmitter, you’ll send the sound of your mics and musical instruments into the mixer, which is set by either a monitoring engineer or the performer. (There are many affordable personal mixers on the market, so it’s easy to make your own mix.)

Why shouldn’t you set up your in-ear monitors without passing the audio through a mixer? A digital mixing console offers several advantages, like:

  • Can EQ (helps boost, cut, or lower frequencies) individual monitor
  • Allows more monitor outputs
  • Allows drummers to run a click track in only one earpiece or pan the signal of other instruments
  • Can save your mixes
  • Can save and remember your settings (beneficial for bands on tour)

Next, you’ll delegate an output to your mics or musical instruments to make it possible to listen to them individually. After that, the monitor mix is fed into the transmitter.

Step 2:

The audio signal from the digital mixing console is routed to your wireless transmitter. Then, this transmitter wirelessly sends the audio signal through its antenna to the receiver that’s worn by the artist around his or her waist like a fanny pack.

Both the transmitter and receiver transmits audio signals through a VHF or UHF radio frequency. Between the two radio frequencies, UHF is better because it produces better-sounding audio and is less vulnerable to interference.

There’s usually a dedicated transmitter for every monitor mix, as well as a receiver for every in-ear monitor. If you set up your transmitters for two mono mixes, you can use the other transmitter to receive two different monitor mixes. On the other hand, multiple receivers can receive one monitor mix.

Step 3:

After picking up the signal from the transmitter, the belt pack receiver converts that signal back into audio. It then amplifies the audio signal through a pair of earpieces. Whether the sound you’ll hear is going to be glorious or not, it mainly depends on the quality of the parts of your in-ear monitor system.

Wired In-Ear Monitors

There are several considerations when choosing an in-ear monitor (IEM) system. For instance, should you go for wired or wireless IEMs? For musicians who don’t need to move around the stage, such as drummers and keyboard players, going wireless may not be important for them.

The concept behind how a wired in-ear monitor works is the same as its wireless counterpart. The only difference is it doesn’t have to deal with radio frequency signals. Wired IEMs are significantly more affordable (since you don’t need a wireless receiver pack) and less stressful to use in challenging RF environments.

Here’s an overview of how it works:

  • If it’s a single wired monitor: Plug your in-ear monitors in the “phones out” input on your digital mixing console.
  • If you want to tweak the volume of each musical instrument, connect your IEMs to the “aux send” input, which you’ll find in the back of your digital mixing console. Turn the aux knobs to adjust the volume of the musical instruments individually.

Note: The number of monitor outputs or aux outputs your in-ear monitor has affects how much individual mixes it can send. So, when choosing an in-ear monitor system, it’s important to know if it gives you the ability to set up a different mix for every performer in your group.


Before we end this article, let’s go over how IEMs work for the last time. From your digital mixing deck, the audio signal configured by you or a monitoring engineer is fed to your transmitter wirelessly. Your transmitter then sends this signal wirelessly via an antenna to the receiver, which is where the earphones are plugged in.

And there you have the basic information on how in-ear monitors work. With this knowledge, we hope it’s easier for you to choose and buy a new or secondhand in-ear monitor [How To Buy A Second Hand In-Ear Monitor].

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