What Are In-Ear Monitors and How Do They Work?

In-ear monitors, or IEMs, are devices similar to earbuds that musicians use for monitoring personalized mixes while performing live. Without IEMs, musicians can have a hard time listening to what they’re playing. IEMs solve this and other stage-related monitoring issues.

There are different types of IEMs and associated monitoring systems. But before exploring the ins and outs of how IEMs work, it’s important to understand what is monitoring and why IEMs are so important for stage musicians.

What is monitoring?

Monitoring is the ability a musician has to listen to what he or she is playing while performing live. To deliver a solid performance on stage, musicians need to be able to accurately listen to what they and their bandmates are playing.

When you go watch a live show, it may seem as though everyone can easily listen to what each musician is doing. But the musicians on the stage don’t listen to the same mix that’s being played to the crowd. The sound the crowd listens to comes through a set of Public Address (PA) speakers that was carefully balanced by an audio engineer.

The musicians are on the other side of the PA speakers. On stage, everything can sound confusing, especially if amplified instruments and drums are involved. The cacophony is such that, without correct monitoring, vocalists, bass players, and keyboard players can have a hard time listening to what they are playing, let alone what their bandmates are doing.

Performing live without monitoring was arguably possible when music was mostly acoustic. But with the dawn of electric and electronic music, the need to find monitoring solutions for musicians became more urgent than ever. That’s when the concept of stage monitors, also known as wedges, was introduced.

What is a stage monitor or wedge?

A wedge is a speaker that’s directed at the musician instead of being directed at the crowd. The mix coming through the wedge can be shaped according to the musician’s needs. The function of a wedge is to help musicians deliver better performances by allowing them to accurately monitor what they and their bandmates are playing.

In simpler terms, wedges are the black speakers that you can usually spot on the stage sitting in front of each musician. The wedges are placed behind the PA speakers and balanced according to the preferences of the band. The monitor mix is usually crafted by the in-house audio engineer, but bigger venues may have a second engineer just for the purpose.

Wedges revolutionized music performance because they allowed musicians to listen more accurately to what was going on on stage. They’re still the norm in the music world, especially for bands that are just starting or playing mostly in small venues. However, wedges are far from being the ideal monitoring solution.

The problem with wedges

Imagine you’re Alex Van Halen, the drummer of Van Halen, in the mid-90s. You’re touring the globe and performing live every week with nothing but wedges. Because your drums are extremely loud and you want to listen to what your bandmates are doing, you need your wedges to be even louder. This is causing some serious damage to your ears (probably the biggest disadvantage of music we can think of).

What’s even worse is that your wedges are so loud that they get picked up by your drums’ microphones, generating nasty feedback that hurts your performance. And if that wasn’t enough, you can’t just move around freely because your stage mix will change drastically according to your position on stage.

This is more than a hypothetical scenario. After all, Alex Van Halen did struggle with stage monitoring in the mid-90s and was responsible for ordering the first pair of custom IEMs. It was then that Ultimate Ears created the first set of professional IEMs, helping Alex Van Halen and thousands of other musicians to deal with pretty much all of their monitoring issues.

IEMs vs. stage monitors or wedges

Both IEMs and wedges can reproduce personalized mixes that were carefully crafted by an audio engineer. But the big difference between IEMs and wedges is that IEMs are earbuds each musician can put on his or her ear, while wedges are speakers that sit on a certain area of the stage.

This crucial difference solves pretty much all the wedge issues identified by Alex Van Halen and countless other musicians. These are the main reasons why IEMs are better than wedges as a monitoring solution:

  • Low volume – Because IEMs are placed inside the ear, musicians don’t need to crank up the volume to accurately listen to their personalized mixes. This means they won’t hurt their ears while performing live, avoiding serious issues such as tinnitus.
  • Noise cancellation – Everyone who’s ever used a pair of Apple Earpods knows that earbuds are very good at canceling ambient noise. When using IEMs, musicians are less exposed to the cacophony happening around them on stage, meaning they can listen to their personalized mixes more precisely.
  • No feedback – While the sound coming from wedges will be picked up by the microphones on stage, IEMs won’t make any noise. This means that the possibility of mic feedback is virtually null when all the musicians on stage are using IEMs instead of wedges.
  • Freedom to move around – Because IEMs sit inside the musician’s ear, he or she is free to move around the stage without impacting his or her monitoring mix. This means that the musicians can interact with the audience and their bandmates without hurting their personalized monitoring mixes.

How do IEMs work?

Contrary to over-ear headphones, IEMs are very small. For that reason, they’re powered by balanced armature (BA) drivers that use an electronic signal to vibrate a reed balanced between two magnets. The reed’s motion is later transferred to a diaphragm that delivers a clear sound signal to the ear.

Over-ear headphones are big enough to hold a pair of small loudspeakers. But because they need to fit inside a person’s ear, IEMs have to rely on BA drivers. These BA drivers aren’t all the same, as they carry different frequencies. Some BA drivers are better prepared for dealing with low frequencies, others mid frequencies, and so forth.

For this reason, musicians tend to pay extra to get IEMs with plenty of BA drivers. However, it’s possible to get a good mix out of IEMs with as few as three or five BA drivers, especially if you can count on the help of a talented audio engineer.

IEMs vs. over-ear headphones

Because they have larger speakers and a format that offers a higher level of ambient-noise cancellation, over-ear headphones deliver better sound quality than IEMs. However, they’re not used on stage for aesthetic reasons.

One thing is to go watch a DJ set and see the DJ wearing a set of over-ear headphones. Another is to pay to see your favorite band perform live and realize they all look like they’re ready for a LAN party.

Even though IEMs are more limited than over-ear headphones in terms of sound quality, they do make musicians look better and move more freely on stage. That’s why IEMs are the monitoring standard instead of over-ear headphones.

You can learn more about this topic here.

Universal IEMs vs. custom IEMs

Universal IEMs can be used by anybody and are designed to fit the standard human ear. They’re readily available in most music stores. Custom IEMs are specifically designed for a musician’s ear. They need to be ordered beforehand and doing so includes an obligatory visit to an audiologist who will scan and create a custom mold of your ears.

Custom IEMs are much harder to get and more expensive than universal IEMs. However, they have several advantages. They’re more comfortable, they’re easier to clean, and they provide superior noise isolation.

You get it: IEMs are powered by BA drivers and are the ideal monitoring solution for live musicians. But how do they work for real? And how do personalized mixes get there in the first place?

To answer this question, we need to understand how an IEM monitoring system works.

How do IEM monitoring systems work?

IEM monitoring systems are responsible for carrying a sound signal from a mixer into the IEM sitting on the musician’s ear. There are two types of IEM monitoring systems: open and closed, but, they both work similarly.

An IEM monitoring system starts at the mixing console. The mixing console receives the output coming from all the instruments and microphones and can be used for balancing the volume, panning, and effects applied to each channel of sound. It can also be used to route specific balanced mixes into a specific output.

The balanced (or personalized) mix is then directed to a transmitter. The function of the transmitter is to send the balanced signal to a wireless bodypack receiver attached to the musician’s body. The signal from the wireless bodypack receiver is finally picked up by the IEM, ensuring that the mix prepared at the mixing console arrives at the musician’s ear.

In simpler terms, for a wireless IEM system, a musician needs a minimum of four different pieces of gear to make an IEM monitoring system at home: a mixing console, a transmitter, a wireless bodypack receiver, and the IEM itself. You can either buy a complete IEM monitoring system (usually without the mixing console) or each of the pieces separately.

For a wired IEM system, the musician would need a mixing console or audio interface, a cable or cables (XLR or TR/TRS depending on your IEM pack), a wired IEM pack, and the IEM itself.

Naturally, even with wireless IEM system, you also need cables to connect the original output source (i.e., the instruments and microphones) to the mixing console and the mixing console output (i.e., the personalized mix) to the transmitter.

Open vs. closed IEM monitoring systems

Whereas open IEM monitoring systems use the personalized mix coming from the audio engineer’s console, closed IEM monitoring systems rely on the personalized mix coming from an independent mixing console, usually set up by the musician.

Closed IEM monitoring systems are more expensive for groups with multiple musicians or complex setups, but they can be very simple for acts with very basic tech specs, such as live solo music producers, which might only need to use the output from their audio interface or mixer to their IEM pack.

Cloud IEM systems are the standard solution for live musicians. Closed IEM monitoring systems are superior to open IEM monitoring systems for two reasons: they save time and they’re more reliable.

Closed IEM monitoring systems save musicians time because musicians don’t have to make their personalized mixes from scratch before every single performance. Working with an audio engineer to craft the mix that’s going to play in your IEM can take up a lot of time during your soundcheck. With a closed system, you can set up your personalized mix at home once and use it for every live show.

Closed IEM monitoring systems are also more reliable because they help musicians to avoid bad audio engineers. Unless you’re lucky to count on an audio engineer of your own, there’s a good chance you’ll find plenty of bad ones on the road. Having your personalized mix ready to go before even setting foot in the venue is the best way of ensuring a bad audio engineer won’t ruin your monitoring and, consequentially, your live performance.

That said, open IEM systems can simply be way easier for more complicated setups. For example, trying to route the sound from multiple drum mics to a cloud IEM system is not an easy task and it’s probably better to just use the output from the mixing desk.

IEM maintenance

IEMs are pretty expensive, so here are a few tips for taking care of yours:

  • Clean the IEMs after every live performance, as ear wax and sweat can damage the equipment.
  • Pay special attention to wax stored in the IEMs ports, as wax can interfere with the way your personalized mix sounds by muffling certain frequencies.
  • Don’t push the volume of the IEMs too hard. Keep in mind that IEMs are powered by small BA drivers that can be easily damaged. Most importantly, though, continuous exposure to loud sounds can damage your ears.
  • Before buying, choose a brand that offers a good replacement policy, as IEMs tend to break easily (even if they’re expensive).


Accurately listening to what you and your bandmates do on stage is essential for delivering a solid live performance. If you want to do the very best for your fans, snub those old-school wedges and opt for a high-quality closed IEM monitoring system with a nice set of custom wireless IEMs.

Brian Clark

Brian Clark

I’ve been a writer with Musician Wave for six years, turning my 17-year journey as a multi-instrumentalist and music producer into insightful news, tutorials, reviews, and features.

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